The effect of flaxseed supplementation on body weight and body composition: A systematic review and meta-analysis of 45 randomized placebo-controlled trials

Article (PDF Available)inObesity Reviews 18(9) · June 2017with 1,441 Reads
DOI: 10.1111/obr.12550
Cite this publication
Abstract
Flaxseed consumption may be inversely associated with obesity; however, findings of available randomized controlled trials (RCTs) are conflicting. The present study aimed to systematically review and analyse RCTs assessing the effects of flaxseed consumption on body weight and body composition. PubMed, Medline via Ovid, SCOPUS, EMBASE and ISI Web of Sciences databases were searched up to November 2016. Mean changes in body composition indices including body weight, body mass index (BMI) and waist circumference were extracted. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Heterogeneity between studies was assessed with the I(2) test. Publication bias and subgroup analyses were also performed. The quality of articles was assessed via the Jadad scale. A total of 45 RCTs were included. Meta-analyses suggested a significant reduction in body weight (WMD: -0.99 kg, 95% CI: -1.67, -0.31, p = 0.004), BMI (WMD: -0.30 kg m(-2) , 95% CI: -0.53, -0.08, p = 0.008) and waist circumference (WMD: -0.80 cm, 95% CI: -1.40, -0.20, p = 0.008) following flaxseed supplementation. Subgroup analyses showed that using whole flaxseed in doses ≥30 g d(-1) , longer-term interventions (≥12 weeks) and studies including participants with higher BMI (≥ 27 kg m(-2) ) had positive effects on body composition. Whole flaxseed is a good choice for weight management particularly for weight reduction in overweight and obese participants.
Obesity Treatment/Prevention
The effect of flaxseed supplementation on body weight
and body composition: a systematic review and meta-
analysis of 45 randomized placebo-controlled trials
M. Mohammadi-Sartang,
1,2
Z. Mazloom,
1,2
H. Raeisi-Dehkordi,
1,2
R. Barati-Boldaji,
2,3
N. Bellissimo
4
and
J. O. Totosy de Zepetnek
4
1
Department of Clinical Nutrition, School of
Nutrition and Food Sciences, Shiraz University
of Medical Sciences, Shiraz, Iran,
2
Meta-
Research Innovation Office, School of Nutrition
and Food Sciences, Shiraz University of
Medical Sciences, Shiraz, Iran,
3
Department of
Community Nutrition, School of Nutrition and
Food Sciences, Shiraz University of Medical
Sciences, Shiraz, Iran, and
4
School of Nutrition,
Ryerson University, Toronto, Ontario, Canada
Received 3 January 2017; revised 2 March
2017; accepted 9 March 2017
Address for correspondence: Z. Mazloom,
Department of Clinical Nutrition, School of
Nutrition and Food Sciences, Shiraz University
of Medical Sciences, Shiraz, Iran.
Email: zohreh.mazloom@gmail.com
Summary
Flaxseed consumption may be inversely associated with obesity; however,
findings of available randomized controlled trials (RCTs) are conflicting. The
present study aimed to systematically review and analyse RCTs assessing the
effects of flaxseed consumption on body weight and body composition.
PubMed, Medline via Ovid, SCOPUS, EMBASE and ISI Web of Sciences
databases were searched up to November 2016. Mean changes in body
composition indices including body weight, body mass index (BMI) and waist
circumference were extracted. Effect sizes were expressed as weighted mean
difference (WMD) and 95% confidence intervals (CI). Heterogeneity between
studies was assessed with the I
2
test. Publication bias and subgroup analyses
were also performed. The quality of articles was assessed via the Jadad scale.
A total of 45 RCTs were included. Meta-analyses suggested a significant
reduction in body weight (WMD: 0.99 kg, 95% CI: 1.67, 0.31,
p= 0.004), BMI (WMD: 0.30 kg m
2
, 95% CI: 0.53, 0.08, p= 0.008)
and waist circumference (WMD: 0.80 cm, 95% CI: 1.40, 0.20,
p= 0.008) following flaxseed supplementation. Subgroup analyses showed that
using whole flaxseed in doses 30 g d
1
, longer-term interventions (12 weeks)
and studies including participants with higher BMI (27 kg m
2
) had positive
effects on body composition. Whole flaxseed is a good choice for weight
management particularly for weight reduction in overweight and obese
participants.
Keywords: Body mass index, body weight, flax, obesity.
Abbreviations: ALA α-linolenic acid; BMI body mass index; CI confidence
interval; PCOS polycystic ovary syndrome; RCTs randomized controlled trials;
SD standard deviation; SEs standard errors; SDG secoisolariciresinol diglucoside;
WC waist circumference; WMD weighted mean difference.
Introduction
Obesity is a major health concern and an important risk
factor for diabetes, cardiovascular disease and cancer.
According to the World Health Organization in 2014, more
than 1.9 billion adults were overweight (body mass index
[BMI] 25 kg m
2
), and 600 million were obese
(BMI 30 kg m
2
) (1,2). It is predicted that ~1.12 billion
individuals will be obese by 2030 (2). The increasing
prevalence of obesity and its related metabolic abnormalities
(e.g. dyslipidaemia, insulin resistance and hypertension) has
created an urgent need for finding an effective approach to
obesity reviews doi: 10.1111/obr.12550
© 2017 World Obesity Federation Obesity Reviews
reduce obesity (3). A large body of evidence suggests a
potential of utilizing functional foods or dietary
nutraceuticals for the management of obesity and associated
abnormalities (46).
Flaxseed (a.k.a. linseed) is a functional food that is a rich
source of α-linolenic acid (ALA), an omega-3 fatty acid
found in vegetables (7,8). Previous studies have shown
anti-inflammatory, antithrombotic and antiarrhythmic pro-
perties of ALA (9). Flaxseed oil contains 5062% ALA,
while whole flaxseed contains 22% ALA (10). Further,
flaxseed contains a high quantity of soluble dietary fibre
(1113) and is a rich food source of lignan, one of the
three major groups of phytoestrogens (14). Flaxseed and
its components have been shown to be beneficial in
reducing risk of cardiovascular diseases, diabetes, blood
pressure and hyperlipidaemia (1517); its consumption
may also positively influence body weight, and by
extension obesity (1820).
Despite increased research on flaxseed in the last decade,
there are inconsistencies between trials examining its effects
on body composition indices. Some trials suggest an inverse
association between flaxseed consumption and body
composition indices (21,22), while others show no little or
reduction in body composition compared with control
following flaxseed supplementation (2325). The present
study performed a comprehensive systematic review and
meta-analyses of available randomized controlled trials
(RCTs) to help quantify the overall effects of flaxseed
products on body composition indices in adults.
Materials and methods
Search strategy
Preferred Reporting Items for Systematic Reviews and
Meta-Analyses statement guidelines were followed as a
framework for reporting meta-analyses of RCTs (26). A
systematic literature search was conducted in medical
databases including PubMed, Medline via Ovid, SCOPUS,
EMBASE and ISI Web of Sciences up to November 2016
using the following subject headings (MeSH) and non-
MeSH keywords: flax* OR flaxseed* OR flax seed*OR
flax-seed*OR linseed* OR lignan* OR Linum
usitatissimum*(Supporting Information S1). The search
was confined to RCTs exploring the influence of flaxseed
or its products (whole or ground flaxseed, lignin
supplement and flaxseed oil) using the English language,
and only studies among human participants were included.
The reference list of related articles, reviews and meta-
analyses were hand-searched for additional relevant studies.
Two independent investigators (H. R. D. and R. B. B.)
screened titles and abstracts for relevant studies, and
discrepancies were resolved using a third investigator
(M. M. S.). The PubMedsMy NCBI(National Centre
for Biotechnology Information) email alert service was
created for identifying new articles that may be published
after our search.
Inclusion criteria
Publishes studies were included if they met the following
criteria: (i) full-text articles written in the English
language; (ii) RCTs with either parallel or crossover
design; (iii) conducted among adults (age 18 years);
(iv) intervention duration of at least 2 weeks; (v) no use
of hormone replacements, fish oil or ALA in the control
group; and (vi) assessed body weight, BMI and waist
circumference (WC) as outcome measures (sufficient
information including standard deviation [SD], standard
error [SE] or 95% confidence interval [CI] must have been
available at baseline and at end study in both flaxseed
and control group). Studies were not included if we were
unable to extract the net effect of the flaxseed intervention
(i.e. if flaxseed was supplemented as an adjunct to another
supplement, the control group containing that
supplement).
Quality assessment
The quality of eligible studies was evaluated
independently by two investigators (M. M. S. and
Z. M.) using the quantitative 5-point Jadad scale (27).
Articles were assigned 0 or 1 point for each of the
following five criteria: (i) randomization, (ii) suitable
method of randomization, (iii) double blinding, (iv)
suitable method of double blinding and (v) explanation
and reason of withdrawals and dropouts (27). Articles
with scores with 3 and 2 were considered of high and
low quality, respectively (28).
Data extraction
Eligible RCTs were reviewed independently by two
authors (H. R. D. and R. B. B.), and the following data
were extracted using a standardized electronic form: first
authors name, publication year, study location, sample
size (enrolment and number completed), type and dose
of intervention and placebo, study design, duration of
the intervention, patients status and other information
including age and sex. Mean and SD of outcome
measures at study baseline, post-intervention and/or
change between baseline and post-intervention were
recorded. For studies reporting data at multiple doses
or multiple time points, only the highest dose of
supplementation at end study were extracted. Three
studies included a fish oil arm that we did not assess in
accordance with our inclusion criteria (2931).
2Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
Quantitative data synthesis and statistical analysis
We evaluated the influence of flaxseed supplementation on
change of the following outcomes: (i) mass (kg); (ii) BMI
(kg m
2
) and (iii) WC (cm). Effect sizes for the meta-
analysis were defined as weighted mean difference (WMD;
value at end trial minus the value at baseline) and 95%
CI. In the event of no reported SD of the mean difference,
it was calculated as follows: SD = ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
SD baselineðÞ2þ½
p
SD end studyðÞ22RSD baselineSD end studyðÞ:
A correlation coefficient of 0.5 was assumed as this R
value is a conservative estimate between 0 and 1 (32). When
SE was reported in place of SD, we converted it SD for
analyses: SD = SE × ffiffi
n
p, where nis the number of
participants in each group. If interested outcomes were
reported as median and range, all mean and SD values were
estimated using the method described by Hozo et al. (33).
Plot digitizer software was used to extract data when the
outcome variable was presented in graphic form only. Pre-
defined subgroup analyses were performed on different
types of flaxseed, supplementation duration, participant
BMI, participant sex, type of study and quality assessment
using the Jadad scale. Random-effects meta-regression
analysis was performed using an unrestricted maximum
likelihood method to explore the association between
changes in body composition indices and duration and dose
of flaxseed supplementation.
Statistical heterogeneity between studies was evaluated
using CochransQ-test (significance set at p<0.1) and I
2
(50% assumed to indicate substantial heterogeneity
among studies). In the presence of heterogeneity, pooled
effect size was calculated using a random-effects model;
otherwise, we applied a fixed-effects model. Sensitivity
analysis was used to explore the extent to which inferences
might depend on a particular study using the leave-one-
out method (i.e. removing a single trial at a time and
repeating the analyses) (34). Publication bias was assessed
by funnel plot, Beggs rank correlation and Eggers weighted
regression tests. In the event of publication bias, the Duval
and Tweedie trim and filland fail-safe Nmethods were
utilized (35). All statistical analyses were performed using
Comprehensive Meta-Analysis (CMA) V2 software
(Biostat, Englewood, NJ, USA) (36) with a level of
significance of p<0.05.
Results
A total of 2,592 reports were initially identified; after
removing duplicates (n= 1,259), 1,333 articles remained.
Of the 1,333 articles, 1,264 were excluded because they
were either not RCTs in humans or unrelated to our
present meta-analyses according to inclusion criteria. A
total of 69 potentially relevant articles were chosen for
full-text evaluation and detailed examination. Among
the full-text articles evaluated, 24 studies were excluded
for the following reasons: duplicate report (n= 2), not
randomized placebo-controlled studies (n= 2), no
anthropometric measurements performed (n= 17) and
use of flaxseed in combination with other components
without an appropriate control group (n= 3). Forty-five
eligible RCTs with 49 treatment arms were included in
the meta-analyses (2125,30,31,3774). Of these, 28
articles reported effects of flaxseed on weight (21
23,25,31,37,38,40,4345,4749,5154,57,59,62,63,66
68,71), 35 articles on BMI (21,22,24,25,30,31,3739,42
44,4651,53,5562,6466,6871,74) and 13 articles on
WC (21,22,31,39,41,44,48,55,60,61,66,72,73). The study
selection process is shown in Fig. S1.
Characteristics of the included studies
Study characteristics of the 45 eligible articles are presented
in Table S1. Data were pooled from the 45 studies
comprising 48 treatment arms; sample size ranged from 9
to 277. Overall, 2,789 participants were randomly assigned
in these trials, and 2,561 participants (91.82%) completed
the studies. Mean age of the participants ranged from 25.6
to 67 years. Nine of the 45 trials were performed exclusively
on women (31,38,41,43,45,48,51,57,75) and nine on men
(40,44,46,54,56,63,65,70,74), and the remaining trials
included both sexes; however, three studies did not mention
sex composition of participants (58,67,68). Eligible studies
were published between 1995 and 2016, and most of them
were conducted in the USA (31,37,38,46,52,57,60,61,66,70,75),
Canada (22,23,4143,48,50,67), Iran (21,59,69,71,73) and
Brazil (24,39,44,45,49). The remaining studies were conducted
in China (62,72), Australia (40,56,63,74), Greece (64,65),
Germany (47), Denmark (51), Romania (58) India (53) and
Japan (54).
Twenty-two treatment arms used whole
(21,22,24,38,42,44,46,48,49,53,57,67,68,7173), ground
(25,43,45,58,66) or deffated (52) flaxseed for the
intervention. Sunflower seed (38), raw rice (44), collagen
(45), wheat germ (48), manioc flour (49), cassava flour
(24), wheat bran (52,66) and wheat (67) were used for the
control groups. Eighteen treatment arms supplemented
flaxseed oil for the intervention (23,30,31,39,40,47,50,54
56,5961,6365,69,70,74), while the control group was
provided canola oil (50,56), corn oil (54,70), olive oil
(30,40,55,60), soybean oil (31,75), safflower oil (6365),
sunflower oil (23,47), MCT oil (59), n-6 oil (74) or placebo
(22,39). One study used both whole flaxseed and flaxseed
oil (22), and five studies used flaxseed lignan
(37,41,45,51,62); the controls in these studies were assigned
placebo. Three studies (21,72,73) incorporated lifestyle
advice only for the control group, while the intervention
group was assigned lifestyle advice and 30 g d
1
flaxseed.
Two other studies (46,58) provided a low-fat or regular diet
Flaxseed and body composition M. Mohammadi-Sartang et al.3obesity reviews
© 2017 World Obesity Federation Obesity Reviews
for the control group, and the intervention group was
provided the same diet in combination with additional
flaxseed.
A wide range of flaxseed supplementation doses were
utilized in the study designs: whole flaxseed 13 to
90 g d
1
, flaxseed oil 1 to 15.4 g of ALA per day and lignan
50 to 600 mg d
1
. Supplementation duration varied from 3
to 48 weeks. Participant characteristics also varied between
studies, many focusing on special and diseased populations:
metabolic syndrome (70,72,73), type 2 diabetes
(22,30,41,62), cardiovascular disease (42,44,67), obesity
(24,49,66), hyperlipidaemia (38,47,50,52,58,64,65,68,71),
postmenopausal women (45,57), polycystic ovary
syndrome (31), prostate cancer (46), haemodialysis
(25,59), diabetic nephropathy (69), non-alcoholic fatty liver
disease (21), fire-fighters (23), normolipidaemic men (63),
healthy adults (37,40,48,51,5456,60,61,74) and older
adults (39).
Data quality
Twenty-nine trials were classified as high quality
(Jadad score 3) (23,24,30,31,3739,4143,46
49,51,52,54,55,57,59,60,62,63,65), and 16 trials
were of low quality (Jadad score <3)
(21,22,25,40,44,45,50,53,56,58,61,64,66,68,71,73).
The last column of Table 1 provides the quality
assessment results of the studies.
Three of the 45 included articles did not report
randomization (53,58,68), but excluding these three
studies had no impact on the meta-analyses. Thirty-
two studies did not adequately explain the
randomization procedure (21,22,25,3741,43
45,47,4958,60,61,63,64,66,68,70,71,73,74). Twenty
studies reported double blinding (24,30,31,37
39,41,43,4749,51,54,57,59,60,62,67,69,70), but 28
studies did not clearly describe the blinding procedure
(2123,25,31,38,40,42,4447,50,53,54,56,58,60,61,64
66,68,69). Details of dropouts were provided in all the
studies.
Meta-analysis results
Twenty-eight studies with 30 treatment arms including a
total of 1,837 participants reported body weight as an
outcome measure. Pooled results from the random-effects
model showed that a reduction in body weight was
significant following flaxseed consumption (WMD:
0.99 kg, 95% CI: 1.67, 0.31, p= 0.004) with
significant heterogeneity (I
2
= 50.00%, p= 0.001) (Fig. 1A).
Thirty-five trails with 38 treatment arms including a total
of 2,209 participants reported BMI as an outcome measure.
Pooled results from the random-effects model showed that
BMI was reduced in the flaxseed group compared with the
control group (WMD: 0.30 kg m
2
, 95% CI: 0.53,
0.08, p= 0.008), with significant heterogeneity among
the studies (I
2
= 54.93%, p<0.001) (Fig. 1B).
Thirteen studies with 14 treatment arms including a total
of 912 subjects reported WC as an outcome measure.
Pooled results from the random-effects model showed that
WC was reduced following an intervention of flaxseed or
its derivatives (WMD: 0.80 cm, 95% CI: 1.40, 0.20,
p= 0.008), with no significant heterogeneity among the
studies (I
2
= 46.94%, p= 0.027) (Fig. 1C).
Sensitivity analysis
Effect sizes for the influence of flaxseed on body weight
were robust in the sensitivity analysis, suggesting that
omission of each trial did not have a significant effect on
the results (Fig. S2A). However, effects of flaxseed on BMI
and WC were sensitive to studies performed by Yari et al.
(73) and Taylor et al. (22), respectively. Removing these
two studies from the analyses rendered the effect of flaxseed
on BMI and WC non-significant (Fig. S2BC).
Subgroup analysis
Results of the subgroup analyses are summarized in Table 1.
When stratified on the basis of type of intervention (whole
flax, flaxseed oil and lignan), a significant reduction in body
weight was observed in trials using whole flaxseed (WMD:
1.75 kg, 95% CI: 2.87, 0.63, p= 0.002), but not
flaxseed oil (WMD: 0.37 kg, 95% CI: 1.48, 0.74,
p= 0.514) or lignan extract (WMD: 0.20 kg, 95%
CI:0.23, 0.63, p= 0.363). BMI was also decreased in the
interventions using whole flaxseed (WMD: 0.63 kg m
2
,
95% CI: 1.17 to 0.09, p= 0.021), but not flaxseed oil
(WMD: 0.004 kg m
2
, 95% CI: 0.08, 0.09, p= 0.930)
or lignan extract (WMD: 0.10 kg m
2
, 95% CI: 0.06,
0.26, p= 0.234). Finally, WC decreased in studies using
whole flaxseed (WMD: 1.21, 95% CI 1.96, 0.46,
p= 0.001), but not in flaxseed oil (WMD: 0.05, 95%
CI: 1.06, 0.96, p= 0.921).
The subgroup analyses performed to identify the
effective dose of whole flaxseed on body composition
showed that body weight (WMD: 0.21 kg, 95% CI:
0.34, 0.09, p= 0.001) and BMI (WMD: 0.60 kg m
2
,
95% CI: 0.81, 0.39, p<0.001) were reduced in whole
flaxseed doses 30 g d
1
, but not in lower doses. With
regard to duration of supplementation, there was a
reduction in body weight (WMD: 1.50 kg, 95% CI:
2.41, 0.60, p= 0.001), BMI (WMD: 0.44 kg m
2
,
95% CI: 0.73, 0.16, p= 0.002) and WC (WMD:
0.69 cm, 95% CI: 1.61, 0.32, p= 0.003) among
trials with 12 weeks of duration, compared with those
lasting <12 weeks.
4Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
Table 1 Results of subgroup analysis of included randomized controlled trials in meta-analysis of flaxseed supplementation and body composition indices
Variables Type of intervention Duration Baseline BMI Gender RCT type Study quality
Body weight WF FXO LIG 12 <12 27 <27 F M Both RP RC Low (<3) High (3)
No. of comparison 18 7 4 18 12 13 17 7 4 19 22 8 14 16
WMD, 95% CI 1.75, 2.87,
0.63 0.37,
1.48, 0.74
0.20,
0.23, 0.63 1.50, 2.41,
0.0.60
0.138,
0.96, 1.23 1.80,
3.30,
2.35
0.17,
0.46,
0.11
0.46,-
3.04, 2.10
0.72,
6.32,
7.52
1.20,
2.01,
0.39
1.31
2.18,
0.45
0.19,
0.23,
0.62
2.19,
3.68,
0.71
0.15,
0.44,
0.13
pvalue 0.002 0.514 0.363 0.001 0.806 0.019 0.242 0.722 0.610 0.003 0.003 0.378 0.004 0.282
I
2
(%) 61.65 0.00 0.00 69.74 0.00 49.51 0.00 0.00 0.00 68.27 54.69 0.00 50.33 0.00
p-heterogeneity <0.001 0.994 0.944 <0.001 1.00 0.011 0.893 1.00 0.990 <0.001 0.001 1.00 0.016 0.914
BMI WF FXO LIG 12 <12 27 <27 F M Both RP RC Low (<3) High (3)
No. of comparison 19 15 3 19 18 24 13 6 7 25 18 9 14 23
WMD,95% CI 0.63, 1.17
to 0.09
0.004,
0.08, 0.09
0.10,
0.06, 0.26 0.44,:
0.73, 0.16
0.146,
0.35, 0.61 0.55,
1.04,
0.06
0.02,
0.08.
0.14
0.28,
0.54.
0.03
0.16,
0.87,
0.55
0.36,
0.65,
0.07
0.43,
0.73,
0.12
1.00,
0.06,
0.26
0.66,
1.23,
0.08
0.004,
0.07,
0.08
pvalue 0.021 0.925 0.234 0.002 0.565 0.028 0.633 0.028 0.660 0.015 0.005 0.232 0.025 0.918
I
2
(%) 50.24 0.00 0.00 76.46 0.00 66.04 0.00 0.00 18.54 66.34 64.04 0.00 47.26 0.00
p-heterogeneity 0.007 0.548 0.950 <0.001 1.00 <0.001 0.690 0.997 0.288 <0.001 <0.001 0.999 0.026 0.864
WC WF FXO LIG 12 <12 27 <27 F M Both RP RC Low (<3) High (3)
No. of comparison 7 6 1 9 5 9 5 2 1 11 12 2 7 7
WMD, 95% CI 1.21, 95%
CI 1.96, 0.46 0.05, 95%
CI: 1.06,
0.96
1.50,
12.72,
9.72
0.69, 95%
CI: 1.61,
0.32
0.22, 95%
CI: 1.40,
1.86
1.12,
1.97,
0.26
0.50,
1.34,
0.34
1.44,
3.04,
0.16
1.36,
1.68,
3.68
0.80,
1.47,
0.14
0.83,
1.44,
0.22
0.28,
3.75,
3.94
1.82,
2.92,
0.72
0.37,
1.09,
0.34
pvalue 0.001 0.921 0.793 0.003 0.784 0.010 0.245 0.079 0.465 0.017 0.007 0.878 0.001 0.305
I
2
(%) 70.53 0.00 0.00 63.04 0.00 62.17 0.00 0.00 0.00 54.37 54.24 0.00 64.52 0.00
p-heterogeneity 0.002 0.974 1.00 0.006 0.899 0.007 0.676 0.618 1.00 0.016 0.013 0.741 0.010 0.821
BMI, body mass index; F, female; FXO, flaxseed oil; LIG, lignans; M, male; RC, randomized crossover design; RCT, randomized controlled trial; RP, randomized parallel design; WC, waist circumference; WF,
whole flaxseed; WMD, weight mean difference.
Flaxseed and body composition M. Mohammadi-Sartang et al.5obesity reviews
© 2017 World Obesity Federation Obesity Reviews
Figure 1 Forest plot detailing weighted mean difference and 95% confidence intervals (CIs) for the impact of flaxseed supplementation on body
composition indices. BMI, body mass index. [Colour figure can be viewed at wileyonlinelibrary.com]
6Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
When stratified on the basis of BMI status, flaxseed
consumption reduced body weight, BMI and WC among
participants with BMI 27, but not among participants
with BMI <27 (Table 1). We also observed a significant
reduction in BMI in women compared with men, with mean
changes of 0.28 kg m
2
(95% CI: 0.54, 0.03, p= 0.03)
and 0.16 kg m
2
(95% CI: 0.87, 0.55, p= 0.66),
respectively.
A significant reduction in body weight, BMI and WC was
found in studies using a parallel design but not crossover
Figure 2 Meta-regression plots of the association between mean changes in body composition indices and duration of flaxseed supplementation. The
size of each circle is inversely proportional to the variance of change. BMI, body mass index; CI, confidence interval; WC, waist circumference.
Flaxseed and body composition M. Mohammadi-Sartang et al.7obesity reviews
© 2017 World Obesity Federation Obesity Reviews
design when assessing based on the type of RCTs. Finally,
subgroup analyses suggested significant reducing effects of
flaxseed and its derivatives on body weight, BMI and WC
in low-quality studies, but not in high-quality studies.
Meta-regression
The effect of flaxseed intervention on body weight (slope:
0.049; 95% CI: 0.06 to 0.03; p= 0.02), BMI (slope:
0.007; 95% CI: 0.01 to 0.0001; p= 0.046) and WC
(slope: 0.015; 95% CI: 0.11 to 0.04; p= 0.028) were
associated with supplementation duration (Fig. 2AC).
When assessing the influence of flaxseed and flaxseed
derivatives dose (whole flaxseed or flaxseed oil, expressed
as ALA g d
1
and lignan extract), no association effects
were found with body weight, BMI or WC (Table S2).
Publication bias
Funnel plots revealed asymmetry in the meta-analyses of
flaxseed consumption on body weight and BMI, but there
was no sign of publication bias with respect to WC. Using
the trim and fillmethod for adjusting publication bias,
seven and six potentially missing studies were imputed for
the meta-analyses of body weight and BMI, respectively
(Fig. S3). Corrected effect sizes after imputation of
potentially missing studies, as well as results of Eggers
linear regression, Beggs rank correlation and fail-safe N
tests, are summarized in Table S3.
Discussion
The present systematic review and meta-analyses of
RCTs explored the effects of flaxseed product
consumption on body composition indices in adults.
Our major findings indicate that participants ingesting
flaxseed products had lower body weight, BMI and
WC after the intervention than controls. However,
subgroup analyses revealed that body composition
indices were reduced with whole flaxseed consumption
only, in trials lasting 12 weeks, and among participants
with BMI 27 kg m
2
.
Flaxseed is a rich source of plant lignans (primarily
secoisolariciresinol diglucoside [SDG]) (12,13); in fact,
flaxseed contains more than 100 times higher SDG than
most other foods (76). Purified lignans in the form of SDG
have been shown to reduce visceral (abdominal) fat in mice
compared with those not consuming SDG (77). The authors
suggested that the high content of SDG may contribute to
the overall effects of flaxseed via a reduction of mRNA
levels of sterol regulatory element-binding proteins that
are involved in TAG synthesis (77). SDG may also be useful
in regulating adiponectin levels and can prevent or reduce
obesity through increased fat oxidation in skeletal muscle
(77,78). In the present meta-analyses, five studies used
lignin supplements (37,41,45,51,62), but subgroup analysis
revealed that lignan did not have any benefit for body
composition in adults. The limited data on humans make
it difficult to draw conclusions regarding the effects of
lignan on obesity. Further, flaxseed oil did not significantly
reduce body weight, BMI and WC, supporting previous
studies reporting no effects of ALA on body composition
(40,47,54,59).
We did observe reductions in body composition indices
with whole flaxseed, however, possibly owing to the high
fibre content (25% soluble form) (13,79). Dietary fibre,
particularly soluble fibre, has anti-obesity effects that have
been shown to decrease body weight (80). Dietary fibre
may help prevent weight gain or promote weight loss via
delayed gastric emptying, inducing feelings of fullness by
absorbing large amounts of water (81), and/or increasing
the concentration of short chain fatty acids that act to
enhance satiety by a variety of mechanisms (82). Further,
dietary fibre can induce viscosity and reduce re-uptake of
bile acids, subsequently reducing micelle formation and
lipid uptake (83,84).
The present meta-analysis found that duration of
flaxseed supplementation had an effect on body
composition indices. Subgroup analysis showed a
significant reduction in body weight, BMI and WC
following intervention durations of 12 weeks. These
findings may be explained by the subsequent increase in
circulating ALA after flaxseed supplementation. ALA is
converted to eicosapentaenoic acid (20:5 n-3) and
docosahexaenoic acid (22:6 n-3) in the body (85); the
anti-obesity effects of eicosapentaenoic acid and
docosahexaenoic acid have been shown in previous studies
(8688). In the long-term supplementation, concentrations
of these long chain omega-3 fatty acids are increased (89),
potentiating the anti-obesity effects of flaxseed.
Furthermore, dietary fibre consumption leads to a gradual
increase in intestinal gut flora (90), which may enhance
lignan absorption (91) and result in the formation of the
main component of mammalian lignans, enterolactone
(92). An inverse relationship between enterolactone and
obesity has been observed (93,94).
Positive effects of flaxseed interventions were observed
among participants with BMI 27 kg m
2
.These
findings suggest that higher BMI has a potent moderating
impact on the effects of flaxseed consumption on changes
in body composition. In other words, it appears that
individuals with higher BMI were more likely to be
positively affected by the supplementation. Our meta-
analysis also showed that the influence of flaxseed on
BMI was more striking in women than in men; however, as
three articles did not report the sex composition of the
participants, the exact sex-specificity effect of flaxseed
remains unclear.
8Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
Limitations
The present study has several limitations; the findings
should be interpreted with caution. First, our results
showed that body weight, BMI and WC were reduced in
low-quality studies but not in higher-quality studies.
Second, the protocol design differences between studies
may have affected our findings. Crossover trials utilized a
washout period of anywhere between 2 (52) and 12 weeks
(41,62), creating different carry-over effects between trials.
This may, in part, help explain the significant reduction
effect observed in parallel design versus crossover design.
In most of the included crossover studies (seven of 12),
the duration of supplementation was <12 weeks, perhaps
providing explanation as to why we observed a significant
effect of flaxseed on body weight, BMI and WC in studies
lasting 12 weeks but not in lower durations. Third,
significant heterogeneity between studies indicates that
the effects of flaxseed on body weight and BMI are not
uniform, likely owing to employing different
methodologies and assessing different populations. Finally,
more than half the eligible studies had a small sample size
(30 of 44 included studies had a sample size lower than 50
participants).
Further, it should be noted that sensitivity analyses
revealed that the results of BMI and WC were highly
determined by the studies of Yari et al. (73) and Taylor
et al. (22), respectively. It is likely that more studies will
help confirm whether flaxseed and its products affect
BMI and WC.
Conclusions
The current meta-analysis pooled results from 45 RCTs
regarding the effects of flaxseed consumption on body
composition indices; we believe that our findings are
valuable for researchers and clinicians. Our findings show
that supplementation of whole flaxseed for more than
12 weeks in individuals with a BMI higher than 27 kg m
2
may reduce body weight, BMI and WC. Flaxseed
consumption may be a valuable dietary approach for the
prevention and treatment of obesity, and many trials have
explored the effects of flaxseed interventions on body
composition. However, more research is needed with larger
sample sizes, adequate durations and well-designed trials
lasting over 12 weeks in order to confirm the beneficial
effects of flaxseed consumption on body composition.
Future research should determine the ideal quantity of
flaxseed for weight loss.
Acknowledgements
The authorsresponsibilities were as follows: M. M. S. and
Z. M. conceived the study. M. M. S. carried out the literature
search. H. R. D. and R. B. B. carried out data extraction and
independent reviewing. M. M. S. and Z. M. assessed the
quality of included studies. M. M. S. performed data
analysis and interpretation. M. M. S. wrote the manuscript.
Z. M., N. B. and J. T. revised the manuscript. The
manuscript has been read and approved by all authors.
Conflict of interest statement
The research did not receive any specific grant from funding
agencies in the public, commercial or not-for-profit sectors.
The authors declared that they have no potential conflicts of
interest.
Supporting information
Additional Supporting Information may be found online in
the supporting information tab for this article. http://dx.doi.
org/10.1111/obr.12550
Table S1 Demographic characteristics of the included
studies.
Table S2 Meta-regression between changes in body
composition indices and administered doses of various
flaxseed products.
Table S3 Assessment of publication bias in the impact of
flaxseed supplementation on body composition indices.
Figure S1 Flow diagram of the study selection procedure
showing the number of eligible randomized controlled trials
for the meta-analysis of the impact of flaxseed
supplementation on body composition indices.
Figure S2 Leave-one-out sensitivity analysis of the impact of
flaxseed supplementation on body composition indices.
Figure S3 Funnel plots detailing publication bias in the
studies selected for analysis of flaxseeds effects on body
composition indices. Trim and fill method was used to
impute for potentially missing studies. Open circles
represent observed published studies; closed circles
represent imputed unpublished studies. BMI, body mass
index; WC, waist circumference.
References
1. World Health Organization. Obesity and Overweight. Fact
Sheet No 311. Updated March 2013. World Health Organization
Available: http://www.who.int/mediacentre/factsheets/fs311/en/
index html Accessed. 2013.
2. Kelly T, Yang W, Chen C-S, Reynolds K, He J. Global burden of
obesity in 2005 and projections to 2030. Int J Obes 2008; 32:
14311437.
3. Huang H, Chen G, Liao D, Zhu Y, Pu R, Xue X. The effects of
resveratrol intervention on risk markers of cardiovascular health in
overweight and obese subjects: a pooled analysis of randomized
controlled trials. Obes Rev 2016; 17: 1329.
4. Baboota RK, Bishnoi M, Ambalam P et al. Functional food
ingredients for the management of obesity and associated co-
morbidities a review. J Funct Foods 2013; 5: 9971012.
Flaxseed and body composition M. Mohammadi-Sartang et al.9obesity reviews
© 2017 World Obesity Federation Obesity Reviews
5. Hirai S, Takahashi N, Goto T et al. Functional food targeting
the regulation of obesity-induced inflammatory responses and
pathologies. Mediat Inflamm 2010; 2010.
6. Kovacs E, Mela D. Metabolically active functional food
ingredients for weight control. Obes Rev 2006; 7:5978.
7. Oomah BD. Flaxseed as a functional food source. J Sci Food
Agric 2001; 81: 889894.
8. Cunnane SC, Ganguli S, Menard C et al. High α-linolenic acid
flaxseed (Linum usitatissimum): some nutritional properties in
humans. Br J Nutr 1993; 69: 443453.
9. Covington MB. Omega-3 fatty acids. Atlantica 2004; 1: 2.0.
10. Pan A, Yu D, Demark-Wahnefried W, Franco OH, Lin X.
Meta-analysis of the effects of flaxseed interventions on blood
lipids. Am J Clin Nutr 2009; 90: 288297.
11. Bloedon LT, Szapary PO. Flaxseed and cardiovascular risk.
Nutr Rev 2004; 62:1827.
12. Muir AD. Flax lignans analytical methods and how they
influence our understanding of biological activity. J AOAC Int
2006; 89: 11471157.
13. Hall C, Tulbek MC, Xu Y. Flaxseed. Adv Food Nutr Res 2006;
51:197.
14. Adlercreutz H, Fotsis T, Lampe J et al. Quantitative
determination of lignans and isoflavonoids in plasma of
omnivorous and vegetarian women by isotope dilution gas
chromatographymass spectrometry. Scand J Clin Lab Invest
1993; 53:518.
15. Ursoniu S, Sahebkar A, Andrica F et al. Effects of flaxseed
supplements on blood pressure: a systematic review and meta-
analysis of controlled clinical trial. Clin Nutr 2016; 35: 615625.
16. Bassett CM, Rodriguez-Leyva D, Pierce GN. Experimental and
clinical research findings on the cardiovascular benefits of
consuming flaxseed. Appl Physiol Nutr Metab 2009; 34: 965974.
17. Hutchins AM, Brown BD, Cunnane SC, Domitrovich SG,
Adams ER, Bobowiec CE. Daily flaxseed consumption improves
glycemic control in obese men and women with pre-diabetes: a
randomized study. Nutr Res 2013; 33: 367375.
18. de Kleijn MJ, van der Schouw YT, Wilson PW, Grobbee DE,
Jacques PF. Dietary intake of phytoestrogens is associated with a
favorable metabolic cardiovascular risk profile in postmenopausal
US women: the Framingham study. J Nutr 2002; 132: 276282.
19. Yari Z, Rahimlou M, Poustchi H, Hekmatdoost A. Flaxseed
supplementation in metabolic syndrome management: a pilot
randomized, open-labeled, controlled study. Phytother Res 2016;
30: 13391344.
20. Brant LHC, LFMdF C, Velarde LGC, Boaventura GT. Impact
of flaxseed intake upon metabolic syndrome indicators in female
Wistar rats. Acta Cir Bras 2012; 27: 537543.
21. Yari Z, Rahimlou M, Eslamparast T, Ebrahimi-Daryani N,
Poustchi H, Hekmatdoost A. Flaxseed supplementation in non-
alcoholic fatty liver disease: a pilot randomized, open labeled,
controlled study. Int J Food Sci Nutr 2016; 67: 461469.
22. Taylor CG, Noto AD, Stringer DM, Froese S, Malcolmson L.
Dietary milled flaxseed and flaxseed oil improve N-3 fatty acid
status and do not affect glycemic control in individuals with well-
controlled type 2 diabetes. J Am Coll Nutr 2010; 29:7280.
23. Barceló-Coblijn G, Murphy EJ, Othman R, Moghadasian
MH, Kashour T, Friel JK. Flaxseed oil and fish-oil capsule
consumption alters human red blood cell n-3 fatty acid
composition: a multiple-dosing trial comparing 2 sources of n-3
fatty acid. Am J Clin Nutr 2008; 88: 801809.
24. Faintuch J, Bortolotto LA, Marques PC, Faintuch JJ, França JI,
Cecconello I. Systemic inflammation and carotid diameter in obese
patients: pilot comparative study with flaxseed powder and cassava
powder. Nutr Hosp 2011; 26: 208213.
25. Khalatbari Soltani S, Jamaluddin R, Tabibi H et al. Effects of
flaxseed consumption on systemic inflammation and serum lipid
profile in hemodialysis patients with lipid abnormalities. Hemodial
Int 2013; 17: 275281.
26. Moher D, Shamseer L, Clarke M et al. Preferred Reporting
Items for Systematic Review and Meta-Analysis Protocols
(PRISMA-P) 2015 statement. Syst Rev 2015; 4:1.
27. Jadad AR, Moore RA, Carroll D et al. Assessing the quality of
reports of randomized clinical trials: is blinding necessary? Control
Clin Trials 1996; 17:112.
28. Moher D, Cook D, Jadad A et al. Assessing the quality of
reports of randomised trials: implications for the conduct of meta-
analyses. Health Technol Assess (Winch Eng) 1999; 3:i.
29. Zheng JS, Lin M, Fang L et al. Effects of n-3 fatty acid
supplements on glycemic traits in Chinese type 2 diabetic patients:
a double-blind randomized controlled trial. Mol Nutr Food Res
2016; 60: 21762184.
30. McManus RM, Jumpson J, Finegood DT, Clandinin MT, Ryan
EA. A comparison of the effects of n-3 fatty acids from linseed oil
and fish oil in well-controlled type II diabetes. Diabetes Care
1996; 19: 463467.
31. Vargas ML, Almario RU, Buchan W, Kim K, Karakas SE.
Metabolic and endocrine effects of long-chain versus essential
omega-3 polyunsaturated fatty acids in polycystic ovary syndrome.
Metabolism 2011; 60: 17111718.
32. Higgins JP, Green S. Cochrane Handbook for Systematic
Reviews of Interventions. Wiley Online Library, 2008.
33. Hozo SP, Djulbegovic B, Hozo I. Estimating the mean and
variance from the median, range, and the size of a sample. BMC
Med Res Methodol 2005; 5: 13.
34. Sahebkar A. Are curcuminoids effective C-reactive protein-
lowering agents in clinical practice? Evidence from a meta-
analysis. Phytother Res 2014; 28: 633642.
35. Duval S, Tweedie R. Trim and fill: a simple funnel-plot-based
method of testing and adjusting for publication bias in meta-
analysis. Biometrics 2000; 56: 455463.
36. Borenstein M, Hedges L, Higgins J, Rothstein H.
Comprehensive Meta-Analysis version 2, Vol. 104. Biostat:
Englewood, NJ, 2005.
37. Almario RU, Karakas SE. Lignan content of the flaxseed
influences its biological effects in healthy men and women. JAm
Coll Nutr 2013; 32: 194199.
38. Arjmandi BH, Khan DA, Juma S et al. Whole flaxseed consumption
lowers serum LDL-cholesterol and lipoprotein(a) concentrations in
postmenopausal women. Nutr Res 1998; 18:1203
1214.
39. Avelino APA, Oliveira GMM, Ferreira CCD, Luiz RR, Rosa G.
Additive effect of linseed oil supplementation on the lipid profiles of
older adults. Clin Interv Aging 2015; 10: 16791685.
40. Barden AE, Croft KD, Durand T, Guy A, Mueller MJ, Mori
TA. Flaxseed oil supplementation increases plasma F1-
phytoprostanes in healthy men. J Nutr 2009; 139: 18901895.
41. Barre DE, Mizier-Barre KA, Stelmach E et al. Flaxseed lignan
complex administration in older human type 2 diabetics manages
central obesity and prothrombosis an invitation to further
investigation into polypharmacy reduction. J Nutr Metab 2012;
585170: 7.
42. Blackwood DP, LaVallée RK, Al Busaidi A, Jassal DS, Pierce
GN. A randomized trial of the effects of ezetimibe on the absorption
of omega-fatty acids in cardiac disease patients: a pilot study. Clin
Nutr ESPEN 2015; 10: 155159.
43. Brooks JD, Ward WE, Lewis JE et al. Supplementation with
flaxseed alters estrogen metabolism in postmenopausal women to
a greater extent than does supplementation with an equal amount
of soy. Am J Clin Nutr 2004; 79: 318325.
10 Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
44. Cassani RSL, Fassini PG, Silvah JH, Lima CMM, Marchini JS.
Impact of weight loss diet associated with flaxseed on inflammatory
markers in men with cardiovascular risk factors: a clinical study.
Nutr J 2015; 14:5.
45. Colli MC, Bracht A, Soares AA et al. Evaluation of the efficacy
of flaxseed meal and flaxseed extract in reducing menopausal
symptoms. J Med Food 2012; 15: 840845.
46. Demark-Wahnefried W, Polascik TJ, George SL et al. Flaxseed
supplementation (not dietary fat restriction) reduces prostate cancer
proliferation rates on men presurgery. Cancer Epidemiol Biomark
Prev 2008; 17: 35773587.
47. Dittrich M, Jahreis G, Bothor K et al. Benefits of foods
supplemented with vegetable oils rich in alpha-linolenic,
stearidonic or docosahexaenoic acid in hypertriglyceridemic
subjects: a double-blind, randomized, controlled trail. Eur J Nutr
2015; 54:881893.
48. Dodin S, Lemay A, Jacques H, Légaré F, Forest JC, Mâsse B.
The effects of flaxseed dietary supplement on lipid profile, bone
mineral density, and symptoms in menopausal women: a
randomized, double-blind, wheat germ placebo-controlled clinical
trial. J Clin Endocrinol Metab 2005; 90: 13901397.
49. Faintuch J, Horie LM, Barbeiro HV et al. Systemic
inflammation in morbidly obese subjects: response to oral
supplementation with alpha-linolenic acid. Obes Surg 2007; 17:
341347.
50. Gillingham LG, Robinson KS, Jones PJH. Effect of high-oleic
canola and flaxseed oils on energy expenditure and body
composition in hypercholesterolemic subjects. Metabolism 2012;
6: 15981605.
51. Hallund J, Ravn-Haren G, Bügel S, Tholstrup T, Tetens I. A
lignan complex isolated from flaxseed does not affect plasma lipid
concentrations or antioxidant capacity in healthy postmenopausal
women. J Nutr 2006; 136:112116.
52. Jenkins DJA, Kendall CWC, Vidgen E et al. Health aspects of
partially defatted flaxseed, including effects on serum lipids,
oxidative measures, and ex vivo androgen and progestin activity:
a controlled crossover trial. A Am J Clin Nutr 1999; 69: 395402.
53. Katare C, Saxena S. Amelioration of selected cardiac risk
factors through supplementation of diet with flaxseed and soya
bean. Int J Nutr Pharmacol Neurol Dis 2013; 3: 352.
54. Kawakami Y, Yamanaka-Okumura H, Naniwa-Kuroki Y,
Sakuma M, Taketani Y, Takeda E. Flaxseed oil intake reduces
serum small dense low-density lipoprotein concentrations in
Japanese men: a randomized, double blind, crossover study. Nutr
J2015; 14: 39.
55. Kontogianni MD, Vlassopoulos A, Gatzieva A et al. Flaxseed
oil does not affect inflammatory markers and lipid profile
compared to olive oil, in young, healthy, normal weight adults.
Metabolism 2013; 62: 686693.
56. Li D, Sinclair A, Wilson A et al. Effect of dietary α-linolenic
acid on thrombotic risk factors in vegetarian men. Am J Clin Nutr
1999; 69: 872882.
57. Lucas EA, Wild RD, Hammond LJ et al. Flaxseed improves
lipid profile without altering biomarkers of bone metabolism in
postmenopausal women. J Clin Endocrinol Metab 2002; 87:
15271532.
58. Mandaşescu S, Mocanu V, DăscaliţaAet al. Flaxseed
supplementation in hyperlipidemic patients. Rev Med Chir Soc
Med Nat Iasi 2004; 109: 502506.
59. Mirfatahi M, Tabibi H, Nasrollahi A, Hedayati M,
Taghizadeh M. Effect of flaxseed oil on serum systemic and
vascular inflammation markers and oxidative stress in hemodialysis
patients: a randomized controlled trial. Int J Nephrol Urol 2016;
48: 13351341.
60. Nelson TL, Hokanson JE, Hickey MS. Omega-3 fatty acids
and lipoprotein associated phospholipase A2 in healthy older adult
males and females. Eur J Nutr 2011; 50: 185193.
61. Nelson TL, Stevens JR, Hickey MS. Adiponectin levels are
reduced, independent of polymorphisms in the adiponectin gene,
after supplementation with alpha-linolenic acid among healthy
adults. Metabolism 2007; 56: 12091215.
62. Pan A, Sun J, Chen Y et al. Effects of a flaxseed-derived lignan
supplement in type 2 diabetic patients: a randomized, double-blind,
cross-over trial. PLoS One 2007; 2e1148.
63. Pang D, Allman-Farinelli M, Wong T, Barnes R, Kingham K.
Replacement of linoleic acid with α-linolenic acid does not alter
blood lipids in normolipidaemic men. Br J Nutr 1998; 80:
163167.
64. Paschos GK, Zampelas A, Panagiotakos DB et al. Effects of
flaxseed oil supplementation on plasma adiponectin levels in
dyslipidemic men. Eur J Nutr 2007; 46: 315320.
65. Rallidis LS, Paschos G, Liakos GK, Velissaridou AH,
Anastasiadis G, Zampelas A. Dietary alpha-linolenic acid
decreases C-reactive protein, serum amyloid A and
interleukin-6 in dyslipidaemic patients. Atherosclerosis 2003;
167: 237242.
66. Rhee Y, Brunt A. Flaxseed supplementation improved insulin
resistance in obese glucose intolerant people: a randomized
crossover design. Nutr J 2011; 10: 44.
67. Rodriguez-Leyva D, Weighell W, Edel AL et al. Potent
antihypertensive action of dietary flaxseed in hypertensive patients.
Hypertension 2013; 62: 10811089.
68. Saxena S, Katare C. Evaluation of flaxseed formulation as a
potential therapeutic agent in mitigation of dyslipidemia. Biom J
2014; 37: 386390.
69. Soleimani A, Taghizadeh M, Bahmani F, Badroj N, Asemi Z.
Metabolic response to omega-3 fatty acid supplementation in
patients with diabetic nephropathy: a randomized, double-blind,
placebo-controlled trial. Clin Nutr 2015; 10:16.
70. Tint D, Anghel M, Lupu D, Fischer L, Niculescu M. Low dose
flaxseed oil supplementation alters the fatty acids profile and the
progression of metabolic syndrome in men without adequate
medical treatment. J Nutr Disord Ther 2011; S7.
71. Torkan M, Hassan Entezari M, Siavash M. Effect of flaxseed
on blood lipid level in hyperlipidemic patients. Rev Recent Clin
Trials 2015; 10:6167.
72. Wu H, Pan A, Yu Z et al. Lifestyle counseling and
supplementation with flaxseed or walnuts influence the
management of metabolic syndrome. J Nutr 2010; 140:
19371942.
73. Yari Z, Rahimlou M, Poustchi H, Hekmatdoost A. Flaxseed
supplementation in metabolic syndrome management: a pilot
randomized, open-labeled, controlled study. Phytother Res 2016;
30: 13391344.
74. Mantzioris E, James MJ, Gibson RA, Cleland LG. Dietary
substitution with an alpha-linolenic acid-rich vegetable oil increases
eicosapentaenoic acid concentrations in tissues. Am J Clin Nutr
1994; 59: 13041309.
75. Karakas SE, Perroud B, Kind T, Palazoglu M, Fiehn O.
Changes in plasma metabolites and glucose homeostasis during
omega-3 polyunsaturated fatty acid supplementation in women
with polycystic ovary syndrome. BBA Clinical 2016; 5:
179185.
76. Bhathena SJ, Velasquez MT. Beneficial role of dietary
phytoestrogens in obesity and diabetes. Am J Clin Nutr 2002; 76:
11911201.
77. Fukumitsu S, Aida K, Ueno N, Ozawa S, Takahashi Y, Kobori
M. Flaxseed lignan attenuates high-fat diet-induced fat
Flaxseed and body composition M. Mohammadi-Sartang et al.11obesity reviews
© 2017 World Obesity Federation Obesity Reviews
accumulation and induces adiponectin expression in mice. Br J
Nutr 2008; 100: 669676.
78. Prasad K. Reduction of serum cholesterol and
hypercholesterolemic atherosclerosis in rabbits by
secoisolariciresinol diglucoside isolated from flaxseed. Circulation
1999; 99: 13551362.
79. Thompson LU, Cunnane SC. Flaxseed in Human Nutrition.
AOCS Press, 2003.
80. Howarth NC, Saltzman E, Roberts SB. Dietary fiber and
weight regulation. Nutr Rev 2001; 59: 129139.
81. Kristensen M, Jensen MG. Dietary fibres in the regulation of
appetite and food intake. Importance of viscosity Appetite 2011;
56:6570.
82. Sleeth ML, Thompson EL, Ford HE, Zac-Varghese SE, Frost
G. Free fatty acid receptor 2 and nutrient sensing: a proposed role
for fibre, fermentable carbohydrates and short-chain fatty acids in
appetite regulation. Nutr Res Rev 2010; 23: 135145.
83. Kristensen M, Jensen MG, Aarestrup J et al. Flaxseed dietary
fibers lower cholesterol and increase fecal fat excretion, but
magnitude of effect depend on food type. Nutr Metab 2012; 9:1.
84. Theuwissen E, Mensink RP. Water-soluble dietary fibers and
cardiovascular disease. Physiol Behav 2008; 94: 285292.
85. Burdge G. α-Linolenic acid metabolism in men and women:
nutritional and biological implications. Curr Opin Clin Nutr Metab
Care 2004; 7: 137144.
86. Garaulet M, Hernández-Morante J, Tébar F, Zamora S.
Anthropometric indexes for visceral fat estimation in
overweight/obese women attending to age and menopausal status.
J Physiol Biochem 2006; 62: 245252.
87. Buckley JD, Howe P. Anti-obesity effects of long-chain omega-
3 polyunsaturated fatty acids. Obes Rev 2009; 10: 648659.
88. Buckley JD, Howe PR. Long-chain omega-3 polyunsaturated
fatty acids may be beneficial for reducing obesity a review.
Nutrients 2010; 2: 12121230.
89. Wien M, Rajaram S, Oda K, Sabaté J. Decreasing the linoleic
acid to α-linolenic acid diet ratio increases eicosapentaenoic acid
in erythrocytes in adults. Lipids 2010; 45: 683692.
90. Kuo S-M. The interplay between fiber and the intestinal
microbiome in the inflammatory response. Adv Nutr: An Intern
Rev J 2013; 4:1628.
91. Muir A, Westcott N, Ballantyne K, Northrup S. Flax lignans:
recent developments in the analysis of lignans in plant and animal
tissues. Proc Flax Inst of the USA 2000; 58:2332.
92. Setchell K, Adlercreutz H. Mammalian lignans and phyto-
oestrogens recent studies on their formation, metabolism and
biological role in health and role of the gut flora in toxicity and
cancer. 1988; 315.
93. Horner NK, Kristal AR, Prunty J, Skor HE, Potter JD, Lampe
JW. Dietary determinants of plasma enterolactone. Cancer
Epidemiol Biomark Prev 2002; 11: 121126.
94. Morisset A-S, Lemieux S, Veilleux A, Bergeron J, Weisnagel SJ,
Tchernof A. Impact of a lignan-rich diet on adiposity and insulin
sensitivity in post-menopausal women. Br J Nutr 2009; 102:
195200.
12 Flaxseed and body composition M. Mohammadi-Sartang et al.obesity reviews
© 2017 World Obesity FederationObesity Reviews
  • Article
    Full-text available
    • Siti Raihanah Shafie
      Siti Raihanah Shafie
    • Stephen Wanyonyi
      Stephen Wanyonyi
    • Sunil Panchal
      Sunil Panchal
    • Lindsay Brown
    Linseed is a dietary source of plant-based ω–3 fatty acids along with fiber as well as lignans including secoisolariciresinol diglucoside (SDG). We investigated the reversal of signs of metabolic syndrome following addition of whole linseed (5%), defatted linseed (3%), or SDG (0.03%) to either a high-carbohydrate, high-fat or corn starch diet for rats for the final eight weeks of a 16–week protocol. All interventions reduced plasma insulin, systolic blood pressure, inflammatory cell infiltration in heart, ventricular collagen deposition, and diastolic stiffness but had no effect on plasma total cholesterol, nonesterified fatty acids, or triglycerides. Whole linseed did not change the body weight or abdominal fat in obese rats while SDG and defatted linseed decreased abdominal fat and defatted linseed increased lean mass. Defatted linseed and SDG, but not whole linseed, improved heart and liver structure, decreased fat vacuoles in liver, and decreased plasma leptin concentrations. These results show that the individual components of linseed produce greater potential therapeutic responses in rats with metabolic syndrome than whole linseed. We suggest that the reduced responses indicate reduced oral bioavailability of the whole seeds compared to the components.
  • Article
    • Alireza Gheflati
      Alireza Gheflati
    • Elham Adelnia
    • Azadeh Nadjarzadeh
      Azadeh Nadjarzadeh
    Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver diseases associated with unfavorable metabolic profiles and oxidative stress parameters. This study was designed to determine the effects of purslane seeds consumption with a low‐calorie diet on insulin resistance, lipid profile, and oxidative stress indices in patients with NAFLD. This randomized controlled clinical trial was conducted on 54 individuals with NAFLD. Subjects were randomly assigned to consume either 10 g/day of purslane seeds sachet before breakfast and dinner in addition to a low‐calorie diet (n = 27) or only the low‐calorie diet (n = 27) for 8 weeks. Fasting blood samples were collected at the beginning and end of the study to measure relevant variables. Intake of purslane seeds with the low‐calorie diet led to a significant decrease in serum concentrations of fasting blood sugar (FBS; −3.52 ± 10.45 compared with 3.03 ± 9.01 mg/dl, P = 0.017), quantitative insulin sensitivity check index (QUICKI; 0.13 ± 0.27 compared with −0.002 ± 0.016, P = 0.017), total cholesterol (4.33 ± 34.04 compared with 23.48 ± 29.47 mg/dl, P = 0.032), and low‐density lipoprotein cholesterol (LDL‐C; −4.35 ± 22.65 compared with 11.82 ± 16.08 mg/dl, P = 0.004) after intervention. Compared with the control group, purslane seeds consumption with adherence to a low‐calorie diet had beneficial effects on FBS, HOMA‐IR, QUICKI, serum total, and LDL‐C in patients with NAFLD but did not affect other glycemic, lipid profile, and oxidative stress parameters.
  • Article
    Full-text available
    • Noureddin Soltanian
    • Mohsen Janghorbani
      Mohsen Janghorbani
    Background To compare the effects of baked flaxseed versus those who received a placebo on constipation symptom scores, weight, glycemic and lipid control in constipated patients with type 2 diabetes (T2D). Methods In a single-blinded, randomized controlled trial, 53 constipated patients with T2D with body mass index (BMI) 20.5–48.9 kg/m² received either 10 g of flaxseed pre-mixed in cookies twice per day or placebo cookies for 12 weeks. The constipation symptom scores, BMI, fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1c), and lipid profile were determined at the beginning and end of 4, 8, and 12-week period. Constipation was evaluated with a stool diary (ROME III). Results After the 12-week intervention, constipation symptom scores (2.46), weight (− 3.8 kg), BMI (− 1.5 kg/m²), FPG (− 26.7 mg/dl), cholesterol (− 37.3 mg/dl), triglycerides (− 10.4 mg/dl), LDLC (− 21.0 mg/dl), HDLC (4.7 mg/dl), cholesterol/ HDLC ratio (− 1.4 mg/dl) significantly decreased from baseline in the flaxseed group (all P-values < 0.05). The differences of absolute change of constipation symptom scores (2.46 vs. 0.41), weight (− 3.8 vs. 0.0 kg), BMI (− 1.5 vs.-0.1 kg/m²), FPG (− 26.7 vs.-1.9 mg/dl), >HbA1c (− 0.8 vs. 1.0%), cholesterol (− 37.3 vs. -10.4 mg/dl), LDLC (− 21.0 vs. -4.3 mg/dl), and HDLC (4.7 vs. -4.4 mg/dl) between the flaxseed and placebo groups were statistically significant (all P-values < 0.05). The compliance was good and no adverse effects were observed. Conclusion In constipated patients with T2D, flaxseed cookies used as a snack may be a useful tool for decreasing constipation symptoms, weight, glycemic and lipid levels. Trial registration irct.ir: IRCT20110416006202N2.
  • Article
    • Haohai Huang
      Haohai Huang
    • Dan Liao
    • Ying Zou
    • Honggang Chi
    Although several clinical trials studied the efficacy of chitosan on weight loss, controversial results have been found. Herein, we evaluated randomized controlled trials (RCTs) of chitosan consumption in adult participants on body weight and body composition through a meta-analysis with trial sequential analysis (TSA). We searched EMBASE, MEDLINE, Web of Science, and CENTRAL databases. The primary body composition indices including body weight, body mass index (BMI), waist circumference, body fat, and hip circumference were extracted. The quality of included articles was assessed according to the Cochrane risk of bias tool. Data were pooled using the random-effects models and calculated as weighted mean difference (WMD) with 95% confidence intervals (CI). Heterogeneity investigated using I² statistics. TSA, subgroup analyses, sensitivity analysis, meta-regression and publication bias were also evaluated. Overall, 15 eligible trials (18 treatment arms) with 1130 subjects were included. The pooled analyses revealed a significant reduction in body weight (WMD, −0.89 kg; 95% CI, −1.41 to −0.38; P = 0.0006), BMI (WMD, −0.39 kg/m²; 95% CI, −0.64 to −0.14; P = 0.002) and body fat (WMD, −0.69%; 95% CI, −1.02 to −0.35; P = 0.0001) receiving chitosan supplementation. Subgroup analyses also showed that consuming chitosan in dose (>2.4 g/d), shorter-term (<12 weeks), studies with parallel design and studies including participants with obese or overweight had positive effects on body composition. TSA provided conclusive evidence for the benefit of chitosan supplementation. Our findings provided evidence that chitosan consumption might be a useful adjunctive pharmacological therapeutic tool for body weight management particularly in overweight/obese participants. Further well-constructed clinical trials that target body weight and body composition as their primary outcomes are needed.
  • Article
    • Alireza Gheflati
      Alireza Gheflati
    • Mohammad Mohammadi
    • Nahid Ramezani-Jolfaie
    • Azadeh Nadjarzadeh
      Azadeh Nadjarzadeh
    Pomegranate is rich in tannins, polyphenols, flavonoids, and several other types of antioxidant compounds whose role in weight loss has been shown in previous studies. However, the results have been mixed regarding the effects of pomegranate consumption on weight loss. Electronic databases such as PubMed, Scopus, ISI Web of Science, and Google Scholar were systematically searched up to May 2018 for controlled clinical trials assessing the effect of pomegranate consumption on weight loss. A random effects model was used to calculate the weighted mean difference (WMD) and 95% confidence interval (CI) as the difference between the mean for the intervention and control groups. Thirteen randomized controlled trials (including 513 participants) were included in the present meta‐analysis. Compared with the control groups, there was no significant reduction in bodyweight, body mass index, waist circumference, and body fat percentage after pomegranate consumption (WMD = −0.23 kg, 95% CI: −0.94, 0.47, P = 0.515; WMD = −0.12 kg/m², 95% CI: −0.29, 0.03, P = 0.132; WMD = −0.08 cm, 95% CI: −0.33, 0.17, P = 0.534; WMD = −0.05, 95% CI: −1.66, 1.55, P = 0.947, respectively). According to the results of the present systematic review and meta‐analysis, there was no significant effect of pomegranate consumption on weight and body composition indices.
  • Article
    • Hamidreza Raeisi-Dehkordi
      Hamidreza Raeisi-Dehkordi
    • Mojgan Amiri
      Mojgan Amiri
    • Karin H Humphries
    • Amin Salehi-Abargouei
      Amin Salehi-Abargouei
    A number of clinical trials have examined the effect of canola oil (CO) on body composition in recent years; however, the results have been inconsistent. The present investigation aims to examine the effect of CO on body weight (BW) and body composition using a systematic review and meta-analysis of controlled clinical trials. Online databases including PubMed, Scopus, and Google Scholar were searched up to February, 2018 for randomized controlled clinical trials that examined the effect of CO on anthropometric measures and body composition indexes in adults. The Cochrane Collaboration's tool was used to assess the risk of bias in individual studies. A random-effects model was used to evaluate the effect of CO consumption on several outcomes: BW, body mass index, waist circumference, hip circumference, waist-to-hip ratio, android-to-gynoid ratio, and body lean and fat mass. In total, 25 studies were included in the systematic review. The meta-analysis revealed that CO consumption reduces BW [weighted mean difference (WMD) = -0.30 kg; 95% CI: -0.52, -0.08 kg, P = 0.007; n = 23 effect sizes], particularly in participants with type 2 diabetes (WMD = -0.63 kg; 95% CI: -1.09, -0.17 kg, P = 0.007), in studies with a parallel design (WMD = -0.49 kg; 95% CI: -0.85, -0.14 kg, P = 0.006), in nonfeeding trials (WMD = -0.32 kg; 95% CI: -0.55, -0.09 kg, P = 0.006), and when compared with saturated fat (WMD = -0.40 kg; 95% CI: -0.74, -0.06 kg, P = 0.019). CO consumption did not significantly affect any other anthropometric measures or body fat markers (P > 0.05). Although CO consumption results in a modest decrease in BW, no significant effect was observed on other adiposity indexes. Further well-constructed clinical trials that target BW and body composition as their primary outcomes are needed.
  • Article
    • Amin Salehi-Abargouei
      Amin Salehi-Abargouei
    Previous studies on the effect of sesame products consumption on body weight and composition have led to inconsistent results. Relevant databases were searched up to April 2018 to conduct a systematic review and meta-analysis of controlled clinical trials. Data on body weight, body mass index (BMI), body fat percent, waist circumference (WC), hip circumference (HC), waist to hip ratio (WHR), and body adiposity index (BAI) were extracted. Ten studies were included in the systematic review. Sesame products consumption did not significantly affect body weight and BMI (P > 0.05). Only sesame oil significantly decreased the body weight and BMI (P < 0.05). The body fat percent and the BAI were significantly reduced after sesame consumption (P < 0.05). Sesame consumption did not affect other body composition indices (P > 0.05). The present study provided some evidence regarding the beneficial effects of sesame on body adiposity indices. Further studies are still required to confirm our results. Registration code: CRD42017054149.
  • Article
    • José J. van den Driessche
    • Jogchum Plat
      Jogchum Plat
    • Ronald P Mensink
      Ronald P Mensink
    Functional foods can be effective in the prevention of the metabolic syndrome and subsequently the onset of cardiovascular diseases and type II diabetes mellitus. More recently, however, another term was introduced to describe foods with additional health benefits: “superfoods”, for which up to date no generally accepted definition exists. Nonetheless, their consumption might contribute to the prevention of the metabolic syndrome, for example due to the presence of potentially bioactive compounds. This review provides an overview of controlled human intervention studies with foods described as “superfoods” and their effects on metabolic syndrome parameters. First, an Internet search was performed to identify foods described as superfoods. For these superfoods, controlled human interventions trials were identified till April 2017, investigating the effects of superfood consumption on metabolic syndrome parameters: waist circumference or BMI, blood pressure, or concentrations of HDL cholesterol, triacylglycerol or glucose. Seventeen superfoods were identified, including a total of 113 intervention trials: blueberries (8 studies), cranberries (8), goji berries (3), strawberries (7), chili peppers (3), garlic (21), ginger (10), chia seed (5), flaxseed (22), quinoa (1), cocoa (16), maca (1), spirulina (7), wheatgrass (1), acai berries (0), hemp seed (0) and bee pollen (0). Overall, limited evidence was found for effects of the foods described as superfoods on metabolic syndrome parameters, since results were not consistent or the number of controlled interventions trials was limited. Inconsistencies might have been related to intervention-related factors, such as duration or dose. Furthermore, conclusions may be different if other health benefits are considered.
  • Article
    Full-text available
    • Stela Pudar-Hozo
      Stela Pudar-Hozo
    • Benjamin Djulbegovic
      Benjamin Djulbegovic
    • Iztok Hozo
      Iztok Hozo
  • Article
    • Haohai Huang
      Haohai Huang
    • Guangzhao Chen
      Guangzhao Chen
    • Dan Liao
    • Xiaoyan Xue
    Background: Potential effects of resveratrol consumption on cardiovascular disease risk factors and body weight in overweight/obese adults have not been fully elucidated. Our present analysis was to evaluate the effects of resveratrol consumption on risk markers related to cardiovascular health in overweight/obese Individuals. Methods: Multiple literature databases were systematically searched, and 21 studies were included. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence interval (CI), and heterogeneity was assessed with the I2 test. Publication bias and subgroup analyses were also performed. Results: There were variations in reporting quality of included studies. Resveratrol intervention significantly lowered total cholesterol (WMD, -0.19 mmol/L; 95% CI, -0.32 to -0.06; P = 0.004), systolic blood pressure (WMD, -2.26 mmHg; 95% CI, -4.82 to -0.49; P = 0.02), and fasting glucose (WMD, -0.22 mmol/L; 95% CI, -0.42 to -0.03; P = 0.03). Heterogeneity was noted for these outcomes (35.6%, 38.7% and 71.4%, respectively). Our subgroup analysis showed significant reductions in total cholesterol, systolic blood pressure, diastolic blood pressure, glucose, and insulin in subjects ingesting higher dose of resveratrol (≥300 mg/day). Conclusion: Our finding provides evidence that daily resveratrol consumption might be a candidate as an adjunct to pharmacological management to better prevent and control cardiovascular disease in overweight/obese individuals.
  • Article
    Full-text available
    • Ju-Sheng Zheng
      Ju-Sheng Zheng
    • Mei Lin
      Mei Lin
    • Ling Fang
    • Duo Li
    Scope: To investigate the effects of n-3 fatty acid supplements, both marine and plant-based, on glycemic traits in Chinese type 2 diabetes (T2D) patients. Method and results: In a double-blind randomized controlled trial, 185 recruited Chinese T2D patients were randomized to either fish oil (FO, n = 63), flaxseed oil (FSO, n = 61) or corn oil group (CO, served as control group, n = 61) for 180 days. The patients were asked to take corresponding oil capsules (4 capsules/day), which totally provided 2 g/day of eicosapentaenoic acid + docosahexaenoic acid in FO group and 2.5 g/day of alpha-linolenic acid in FSO group. No group×time interaction was observed for HOMA-insulin resistance, fasting insulin or glucose. Significant group×time interaction (P = 0.035) was observed for glycated haemoglobin (HbA1c), with HbA1c decreased in FO group compared with CO group (P = 0.037). We also found significant group×time interactions for lipid traits, including low-density lipoprotein cholesterol (P = 0.043), total cholesterol (TC) (P = 0.021), total cholesterol/ high-density lipoprotein cholesterol (TC/HDL-C) (P = 0.009) and triacylglycerol (TG) (P = 0.003), with the lipid profiles improved in FO group. No significant effects of FSO on glycemic traits or blood lipids were observed. Conclusions: Marine n-3 PUFA supplements may improve glycemic control and lipid profiles among Chinese type 2 diabetic patients. This article is protected by copyright. All rights reserved.
  • Article
    Full-text available
    • David Moher
    • Larissa Shamseer
    • Mike Clarke
    • Evelyn P Whitlock
      Evelyn P Whitlock
    Systematic reviews should build on a protocol that describes the rationale, hypothesis, and planned methods of the review; few reviews report whether a protocol exists. Detailed, well-described protocols can facilitate the understanding and appraisal of the review methods, as well as the detection of modifications to methods and selective reporting in completed reviews. We describe the development of a reporting guideline, the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Protocols 2015 (PRISMA-P 2015). PRISMA-P consists of a 17-item checklist intended to facilitate the preparation and reporting of a robust protocol for the systematic review. Funders and those commissioning reviews might consider mandating the use of the checklist to facilitate the submission of relevant protocol information in funding applications. Similarly, peer reviewers and editors can use the guidance to gauge the completeness and transparency of a systematic review protocol submitted for publication in a journal or other medium.
  • Article
    • Zahra Yari
      Zahra Yari
    • Mehran Rahimlou
      Mehran Rahimlou
    • Hossein Poustchi
      Hossein Poustchi
    • Azita Hekmatdoost
      Azita Hekmatdoost
    The aim of this study was to evaluate the efficacy of flaxseed supplementation plus lifestyle modification in comparison with lifestyle modification alone in the management of metabolic syndrome (MetS). A randomized controlled clinical trial was conducted on 44 patients with MetS. Participants were assigned to receive either the lifestyle advice and 30-g brown milled flaxseed daily or only the lifestyle advice as the control group. The percentage of individuals with MetS decreased from baseline by 50% and 82% in the control and intervention group, respectively. The reversion rate of central obesity was higher in the flaxseed group (36%) than control group (13%). Moreover, greater reduction in insulin resistance was observed in flaxseed group in comparison with control group (p < 0.001). Body weight, waist circumference, and body mass index decreased significantly in both groups with a significantly greater reduction in flaxseed group in comparison with controls (p < 0.05). There were no significant changes in blood pressure in any groups. Our results indicate that co-administration of flaxseed with lifestyle modification is more effective than lifestyle modification alone in management of MetS; whether these effects will be sustained with longer treatment durations remains to be determined. Copyright © 2016 John Wiley & Sons, Ltd.
  • Article
    • Maryam Mirfatahi
    • Hadi Tabibi
      Hadi Tabibi
    • Alireza Nasrollahi
    • M. Taghizadeh
    Purpose: The aim of this study was to investigate the effects of flaxseed oil consumption on serum systemic and vascular inflammation markers, and oxidative stress in hemodialysis (HD) patients. Methods: In this randomized, double-blind, clinical trial, 34 HD patients were randomly assigned to either the flaxseed oil or the control group. The patients in the flaxseed oil group received 6 g/day flaxseed oil for 8 week, whereas the control group received 6 g/day medium-chain triglycerides (MCT) oil. At baseline and the end of week 8, serum concentrations of high-sensitive C-reactive protein (hs-CRP), soluble intercellular adhesion molecule type 1 (sICAM-1), soluble vascular cell adhesion molecule type 1 (sVCAM-1), sE-selectin, and malondialdehyde (MDA) were measured after a 12- to 14-h fast. Results: Serum hs-CRP, a systemic inflammation marker, and sVCAM-1, a vascular inflammation marker, reduced significantly in the flaxseed oil group at the end of week 8 compared to baseline (P < 0.05), and the reductions were significant in comparison with the MCT oil group (P < 0.05). There were no significant differences between the two groups in mean changes in serum sICAM-1, sE-selectin, and MDA. Conclusion: This study indicates that daily consumption of 6 g flaxseed oil reduces serum hs-CRP and sVCAM-1, which are two risk factors for CVD. Therefore, the inclusion of flaxseed oil in the usual diet of HD patients can be considered as a strategy for reducing CVD risk factors.
  • Article
    Full-text available
    • Sidika E. Karakas
    • Bertrand Perroud
    • Tobias Kind
      Tobias Kind
    • Oliver Fiehn
      Oliver Fiehn
    Background: Both fish (FO) and flaxseed oils (FLX) are n-3 polyunsaturated fatty acids (PUFA). Fish oil contains long chain while FLX contains essential n-3 PUFA. We demonstrated that FO altered insulin secretion and resistance in polycystic ovary syndrome (PCOS) women but FLX did not. Surprisingly, the effects of FO were similar to those of the n-6 PUFA-rich soybean oil (SBO). Since increased branched chain (BCAA) and aromatic amino acids (AA) affect insulin secretion and resistance, we investigated whether FO, FLX and /or SBO affect plasma metabolites, especially AA. Methods and findings: In this six-week, randomized, 3-parallel arm, double-blinded study, 54 women received 3.5 g/day FO, FLX or SBO. In 51 completers (17 from each arm), fasting plasma metabolites were measured at the beginning and at the end. As compared to FLX, FO and SBO increased insulin response and resistance as well as several BCAA and aromatic AA. Pathway analysis indicated that FO exerted the largest biochemical impact, affecting AA degradation and biosynthesis, amine, polyamine degradation and alanine, glycine, l-carnitine biosynthesis and TCA cycle, while FLX had minimal impact affecting only alanine biosynthesis and l-cysteine degradation. Conclusion: Effects of FO and SBO on plasma AA were similar and differed significantly from those of the FLX. The primary target of dietary PUFA is not known. Dietary PUFA may influence insulin secretion and resistance directly and alter plasma AA indirectly. Alternatively, as a novel concept, dietary PUFA may directly affect AA metabolism and the changes in insulin secretion and resistance may be secondary.
  • Article
    • Gwendolyn Barceló-Coblijn
      Gwendolyn Barceló-Coblijn
    • Eric J Murphy
      Eric J Murphy
    • Rgia A Othman
      Rgia A Othman
    • James K Friel
      James K Friel
    Background: An increase in plasma n–3 fatty acid content, particularly eicosapentaenoic acid (20:5n–3; EPA) and docosahexaenoic acid (22:6n–3; DHA), is observed after consumption of fish oil–enriched supplements. Because α-linolenic acid (18:3n–3; ALA) is the direct precursor of EPA and DHA, ALA-enriched supplements such as flax may have a similar effect, although this hypothesis has been challenged because of reported low conversion of ALA into DHA. Objective: To address this question, we designed a clinical trial in which flax oil, fish-oil, and sunflower oil (placebo group) capsules were given to firefighters (n = 62), a group traditionally exposed to cardiovascular disease risk factors. Design: Firefighters were randomly divided into 6 experimental groups receiving 1.2, 2.4, or 3.6 g flax oil/d; 0.6 or 1.2 g fish oil/d; or 1 g sunflower oil/d for 12 wk. Blood was drawn every 2 wk, and the total phospholipid fatty acid composition of red blood cells was determined. Results: As expected, fish oil produced a rapid increase in erythrocyte DHA and total n–3 fatty acids. The consumption of either 2.4 or 3.6 g flax oil/d (in capsules) was sufficient to significantly increase erythrocyte total phospholipid ALA, EPA, and docosapentaenoic acid (22:5n–3) fatty acid content. There were no differences among groups in plasma inflammatory markers or lipid profile. Conclusions: The consumption of ALA-enriched supplements for 12 wk was sufficient to elevate erythrocyte EPA and docosapentaeoic acid content, which shows the effectiveness of ALA conversion and accretion into erythrocytes. The amounts of ALA required to obtain these effects are amounts that are easily achieved in the general population by dietary modification.
  • Article
    Full-text available
    • Zahra Yari
      Zahra Yari
    • Mehran Rahimlou
      Mehran Rahimlou
    • Tannaz Eslamparast
      Tannaz Eslamparast
    • Azita Hekmatdoost
      Azita Hekmatdoost
    A two-arm randomized open labeled controlled clinical trial was conducted on 50 patients with non-alcoholic fatty liver disease (NAFLD). Participants were assigned to take either a lifestyle modification (LM), or LM +30 g/day brown milled flaxseed for 12 weeks. At the end of the study, body weight, liver enzymes, insulin resistance and hepatic fibrosis and steatosis decreased significantly in both groups (p< 0.05); however, this reduction was significantly greater in those who took flaxseed supplementation (p < 0.05). The significant mean differences were reached in hepatic markers between flaxseed and control group, respectively: ALT [-11.12 compared with -3.7 U/L; P< 0.001], AST [-8.29 compared with -4 U/L; p < 0.001], GGT [-15.7 compared with -2.62 U/L; p < 0.001], fibrosis score [-1.26 compared with -0.77 kPa; p = 0.013] and steatosis score [-47 compared with -15.45 dB/m; p = 0.022]. In conclusion, flaxseed supplementation plus lifestyle modification is more effective than lifestyle modification alone for NAFLD management.