Effect of chia seed (Salvia hispanica l.) consumption on cardiovascular risk factors in humans: A systematic review

Abstract

Introduction:
chia is a seed rich in such nutrients as proteins, n-3 fatty acids and especially alpha-linolenic acid (ALA), minerals, fibers and antioxidants. Efforts have been made to assess whether human consumption of chia can reduce cardiovascular risk factors; however, it has not been established as effective and the findings of the few studies to have looked into the matter are inconsistent.

Aim:
to systematize the findings of studies assessing the effect the consumption of chia seed, either milled or whole, has in the prevention/control of cardiovascular risk factors in humans.

Methods:
this is a systematic literature review (SLR) with no meta-analysis. The articles scrutinizedwere identified in the electronic databases Lilacs, Medline (Pub- Med version), Cochrane, Scielo, Scopus, and Web of Science under the keywords"dyslipidemia" or "dislipidemia", "hyperlipidemia" or "hiperlipidemia", "obesity" or "obesidade", "salvia"or"salviahispanica", "Lamiaceae" or "chia", "hypertension" or "hipertensão", "hypertrygliceridemia" or "hipertrigliceridemia", and "riscocardiovascular" or "cardiovascularrisk." We chose for our selection English-, Portuguese- or Spanish-language articles about clinical trials on humans and published within the last ten years. The biases of risk analysis were carried out considering 6 of the 8 criteria of the Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.

Findings:
seven studies (n = 200) fit our inclusion criteria. Of the chosen clinical trials, only one was not randomized. Five of the studies were blind experiments. Two of the studies were acute trials, both of them randomized. Of the chia seed interventions, one study showed a significant drop in systolic blood pressure (SBP) and inflammatory markers, yet there was no change in body mass, lipid profile or blood sugar. In four of the studies reviewed there was a significant spike in ALA and eicosapentaenoic acid (EPA), with no significant change to other parameters. In the acute trials, post-prandial blood sugar was significantly lower. Only one study showed a significant drop in triglycerides (TG), body mass and inflammatory markers; however, the chia seed in that case was mixed with other foods. Most of the studies showed unclear or low risk of bias. Two studies showed a high risk of bias because not all the pre-specified primary outcomes were reported in the findings.

Conclusion:
most of the studies did not demonstrate statistically significant results in relation to cardiovascular disease (CVD) risk factors. The evidence regarding the relationship between chia seed consumption and cardiovascular risk factors are insufficient, and the studies included in this review present numerous limitations. Further research is hence needed.

Full text

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1909
Nutr Hosp. 2015;32(5):1909-1918
ISSN 0212-1611 • CODEN NUHOEQ
S.V.R. 318
Revisión
Effect of chia seed (Salvia hispanica L.) consumption on cardiovascular
risk factors in humans: a systematic review
Cynthia de Souza Ferreira, Lucilia de Fátima de Sousa Fomes, Gilze Espirito Santo da Silva and
Glorimar Rosa
Postgraduate Nutrition Program, Josué de Castro Institute of Nutrition, Federal University of Rio de Janeiro, Brazil.
Abstract
Introduction: chia is a seed rich in such nutrients as
proteins, n-3 fatty acids and especially alpha-linolenic
acid (ALA), minerals, fibers and antioxidants. Efforts
have been made to assess whether human consumption
of chia can reduce cardiovascular risk factors; however,
it has not been established as effective and the findings
of the few studies to have looked into the matter are in-
consistent.
Aim: to systematize the findings of studies assessing
the effect the consumption of chia seed, either milled or
whole, has in the prevention/control of cardiovascular
risk factors in humans.
Methods: this is a systematic literature review (SLR)
with no meta-analysis. The articles scrutinizedwere iden-
tified in the electronic databases Lilacs, Medline (Pub-
Med version), Cochrane, Scielo, Scopus, and Web of
Science under the keywords”dyslipidemia” or “dislipide-
mia”, “hyperlipidemia” or “hiperlipidemia”, “obesity” or
“obesidade”, “salvia”or”salviahispanica”, “Lamiaceae”
or “chia”, “hypertension” or “hipertensão”, “hypertry-
gliceridemia” or “hipertrigliceridemia”, and “riscocar-
diovascular” or “cardiovascularrisk.” We chose for our
selection English-, Portuguese- or Spanish-language arti-
cles about clinical trials on humans and published within
the last ten years. The biases of risk analysis were carried
out considering 6 of the 8 criteria of the Cochrane Hand-
book for Systematic Reviews of Interventions Version 5.1.
Findings: seven studies (n = 200) fit our inclusion
criteria. Of the chosen clinical trials, only one was not
randomized. Five of the studies were blind experiments.
Two of the studies were acute trials, both of them rando-
mized. Of the chia seed interventions, one study showed
a significant drop in systolic blood pressure (SBP) and
inflammatory markers, yet there was no change in body
mass, lipid profile or blood sugar. In four of the studies
reviewed there was a significant spike in ALA and eico-
sapentaenoic acid (EPA), with no significant change to
other parameters. In the acute trials, post-prandial blood
EFECTOS DEL CONSUMO DE LA SEMILLA
DE CHÍA (SALVIA HISPANICA L.) EN LOS
FACTORES DE RIESGO CARDIOVASCULAR EN
HUMANOS: UNA REVISIÓN SISTEMÁTICA
Resumen
Introducción: la chía es una semilla rica en nutrientes
tales como proteínas; ácidos grasos omega 3, especial-
mente ácido alfa-linolénico (ALA); minerales; fibras y
antioxidantes. Se han hecho esfuerzos para evaluar si el
consumo humano de chía puede reducir los factores de
riesgo cardiovascular; sin embargo, no se ha establecido
como eficaz y los resultados de los pocos estudios que han
examinado la cuestión son incompatibles.
Objetivo: sistematizar los hallazgos de los estudios que
evaluaron el efecto del consumo de la semilla de chía, ya
sea molida o entera, tiene en la prevención/control de los
factores de riesgo cardiovascular en los seres humanos.
Métodos: se trata de una revisión sistemática de la lite-
ratura (SLR), sin metaanálisis. Los artículos escrutados
eran identificados en las bases de datos Lilacs electróni-
cos, Medline (PubMed versión), Cochrane, Scielo, Scopus
y Web of Science bajo la palabra clave “dyslipidemia”
o “dislipidemia”, “hyperlipidemia” o “hiperlipidemia”,
“obesity” o “obesidade”, “salvia” o “salviahispanica”,
“Lamiaceae” o “chia”, “hypertension” o “hipertensão”,
“hypertrygliceridemia” o “hipertrigliceridemia” y “ris-
cocardiovascular” o “cardiovascularrisk”. Elegimos
para nuestra selección artículos en inglés, portugues o
español sobre ensayos clínicos en seres humanos publi-
cados en los últimos diez años. Los sesgos de análisis de
riesgo se realizaron considerando seis de los ocho crite-
rios del Manual Cochrane para Revisiones Sistemáticas
de Intervenciones Versión 5.1.
Resultados: siete estudios (n = 200) encajan con los cri-
terios de inclusión. De los ensayos clínicos seleccionados,
solo uno no fue aleatorio. Cinco de los estudios fueron ex-
perimentos ciegos. Dos de los estudios eran ensayos agu-
dos, ambos asignados al azar. De las intervenciones de
semillas de chía, un estudio mostró una disminución sig-
nificativa de la presión arterial sistólica (PAS) y los mar-
cadores de inflamación; sin embargo, no hubo cambios
en la masa corporal, el perfil de lípidos o el azúcar en san-
gre. En cuatro de los estudios revisados no había un pico
significativo en ALA y ácido eicosapentaenoico (EPA), ni
ningún cambio significativo en otros parámetros. En los
ensayos agudos, el nivel postprandial de azúcar en sangre
fue significativamente menor. Solo un estudio mostró un
Correspondence: Glorimar Rosa.
Universidade Federal do Rio de Janeiro.
Av. Carlos Chagas Filho, 373- CCS- bloco J, 2.º andar.
Instituto de Nutrição Josué de Castro – DND- sala 25.
Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil.
E-mail: glorimar@nutricao.ufrj.br
Recibido: 13-VII-2015.
Aceptado: 20-VIII-2015.
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1910 Nutr Hosp. 2015;32(5):1909-1918 Cynthia de Souza Ferreira et al.
Introduction
Salvia hispanica L., commonly known as chia, is
an annual plant belonging to the Lamiaceae family.
Originating in such countries as Guatemala, Mexico
and Colombia, chia seed was used and consumed as
a source of energy and incorporated into a number of
foods in the diet of the indigenous Aztec civilization
(Ulbricht et al., 2009).
The lipid content in chia seeds varies from 25% to
40%, with 60% of the total lipids made up of ALA
(n-3) and 20% composed of linoleic acid (n-6) (Bres-
son et al. 2009). When the oil is extracted from the
chia seed, what remains is a significant concentration
of dietary fiber (33.9g/100g) and protein (17g/100g).
(Ayresa& Coates 1999; Craig & Sons 2004).
Of total dietary fiber, the greatest fraction
(53.45g/100g) comprises insoluble fiber, which plays
a role in satiety and proper bowel function (Vázquez
et al. 2008). Rich in magnesium and phenolic com-
pounds (mainly quercetin and kaempferol), chia seed
offers significant antioxidant capacity (Lee A.S. 2009;
Caudillo et al. 2008), while its calcium and potassium
content suggests it may be helpful in controlling high
blood pressure (HBP) (Vuksan et al. 2007).
According to the World Health Organization (WHO
2013), CVD is the world’s number one cause of mor-
tality, with approximately 17 million deaths per year.
In Brazil, CVD causes 21.1% of all deaths (Datasus
2012), as well as being responsible for a great number
of hospitalizations, which results in higher health care
and socioeconomic costs (Schmidt et al. 2011; Brazi-
lian Cardiology Society 2010).
Among the cardiovascular risk factors that can
be modified, controlled or treatedare excess weight
(overweight or obesity), hypertension, dyslipidemia
and diabetes mellitus, with approximately 5% of
worldwide deaths attributed to excess weight (World-
Heart Federation 2012).
When added to the diets of pigs and chickens, chia
seed boosted the levels of n-3 fatty acids and reduced
the amount of cholesterol found in the meat and eggs
(Ayerza et al. 2002; Azeona et al. 2008; Coates et al.
2009). In rats, use of the seed lowered plasma LDL
cholesterol and triglycerides while it elevated plasma
HDL cholesterol (Ayerza et al. 2007) levels.
Most of the studies conducted on humans using chia
seed looked at the relationship between its consump-
tion and the possible effect it could have on cardio-
vascular risk factors, by examining such data as body
composition and mass, lipid profile, blood pressure,
blood sugar and inflammatory markers (Nieman 2009;
Vuksan 2007; Nieman 2012). However, the findings of
the few available studies are controversial, with little
evidence to prove chia seed’s efficacy, and furthermo-
re, most of the studies presenting positive results were
conducted on animals.
Thus, our aim with this SLR is to synthesize the fin-
dings regarding the human use of chia seed and assess
its possible benefits in the prevention/reduction of car-
diovascular risk factors.
Methods
For this SLR we used the current guidelines for sys-
tematic reviews (Liberatti 2009).
We carried out our search from May to July 2014
in the databases Lilacs, Medline (PubMed version),
Cochrane, Scielo, Scopus, and Web of Science by
consulting the following keywords in English and Por-
tuguese: dislipidemias (dyslipidemias), salvia, salvia
hispanica, obesidade (obesity), hipertensão arterial
sistêmica (systemic arterial hypertension), hipertrigli-
sugar was significantly lower. Only one study showed a
significant drop in triglycerides (TG), body mass and in-
flammatory markers; however, the chia seed in that case
was mixed with other foods. Most of the studies showed
unclear or low risk of bias. Two studies showed a high
risk of bias because not all the pre-specified primary out-
comes were reported in the findings.
Conclusion: most of the studies did not demonstrate
statistically significant results in relation to cardiovascu-
lar disease (CVD) risk factors. The evidence regarding
the relationship between chia seed consumption and car-
diovascular risk factors are insufficient, and the studies
included in this review present numerous limitations.
Further research is hence needed.
(Nutr Hosp. 2015;32:1909-1918)
DOI:10.3305/nh.2015.32.5.9394
Key words: Dyslipidemia. Hyperlipidemia. Obesity. Sal-
via. Salvia hispanica. Lamiaceae. Chia seed. Hypertension.
Hypertriglyceridemia. Cardiovascular risk.
descenso significativo de los triglicéridos (TG), la masa
corporal y los marcadores inflamatorios; sin embargo, la
semilla de chía en ese caso se mezcló con otros alimen-
tos. La mayoría de los estudios mostraron riesgos claros
o bajo sesgo. Dos estudios mostraron un alto riesgo de
sesgo, porque no todos los resultados primarios preespe-
cificados fueron reportados en los hallazgos.
Conclusión: la mayoría de los estudios no demostraron
resultados estadísticamente significativos en relación con
los factores de riesgo cardiovascular (ECV). La evidencia
sobre la relación entre el consumo de semillas de chía y los
factores de riesgo cardiovascular son insuficientes, y los
estudios incluidos en esta revisión presentan numerosas
limitaciones. Por lo tanto, se necesita más investigación.
(Nutr Hosp. 2015;32:1909-1918)
DOI:10.3305/nh.2015.32.5.9394
Palabras clave: Dislipidemia. Hiperlipidemia. Obesidad.
Salvia. Salvia hispanica. Lamiaceae. Semillas de chía. Hi-
pertensión. Hipertrigliceridemia. Riesgo cardiovascular.
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1911
Nutr Hosp. 2015;32(5):1909-1918Effects of chia consumption on
cardiovascular risk factors in humans
ceridemia (hypertrigliceridemia), risco cardiovascu-
lar (cardiovascular risk), chia andLamiaceae. We used
the conjunction “And” to associate the use of chia with
cardiovascular risk factors, for example “SALVIA
[descriptor of subject] and DYSLIPIDEMIAS [des-
criptor of object]” (Table I). Two researchers (CSF
and LFSG) analyzed the articles yielded by the search,
independently of each other.
Our inclusion criteria were that the articles had to
be less than 10 years old, written in English, Spanish
or Portuguese, clinical trials on humans, and not litera-
ture reviews. We excluded animal studies, studies that
weren’t clinical trials, and duplicate articles.
Assessment of risk of bias
To assess risk of bias we used Cochrane Handbook
for Systematic Reviews of Interventions Version 5.1
(Higgins 2011), which has areas with ratings “low
risk”, “high risk” and “unclear risk”. The selection of
the 6 criteria was based on the applicability to the se-
lected types of study for this paper.
Collaboration’s tool thereby performing a critical
appraisal of each aspect of the risk separately. The tool
assesses bias according to seven domains: random se-
quence generation, allocation concealment, blinding
of participants and personnel, blinding of outcome
assessment, incomplete outcomes, selective outcome
reporting, and other sources of bias. Each of the do-
mains appraised can be classified into three categories:
low risk of bias, high risk of bias or unclear risk of bias
(Fig. 1).
Assessing outcomes of interest
The outcomes we assessed from the studies were
total cholesterol, high-density lipoprotein (HDL-c),
Table I
Descriptors and concepts used in LRS
Concepts
in português Concepts
in english Descriptors
in portuguese Descriptors
in english (mesh) Synonyms
Dislipidemia - Dyslipidemias Dislipoproteinemias
Hiperlipidemia - Hyperlipidemias Hyperlipemia
Hipertrigliceridemia - Hipertrigliceridemia
Obesidade - Obesity -
SalviaHispanica
Hipertensão Hypertension Hipertensão Hypertension
Chia - - -
Salvia Salvia Salvia Salvia -
Lamiaceae Lamiaceae Lamiaceae
Risco cardiovascular Cardiovascular Risk - -
Potentially relevant studies identified
by keyword on Lilacs(n=13); Pubmed
(n=98); Cochrane(n=6); Scielo(n=17);
Scopus(n=41); e Webof Science (n=25)
N=200
179 studies excluded for being
on animals, in vitro or not being
about salvia hispânica L or chia
Original publications selected for
reading of abstracts on Lilacs(n=0);
Pubmed(n=12); Cochrane(n=0);
Scielo(n=0); Scopus (n=5); Web (n=4)
N=21
Studies excluded for being
systematic revision (n=4);
duplicates(n=2).
Estudos selecionados para leitura do
texto completo no Pubmed(n=11);
Scopus(n=3) e Web ofscience(n=3)
N=17
Exclusão de artigos duplicados
(n= 10)
7 estudos selecionados para leitura do
texto completo: Pubmed (n=3);
Scopus (n=1); Web o Science (n=3)
7 estudos incluídos na revisão sistemática de literatura
Fig. 1.—Flowchart illustrating study search and selection pro-
cess.
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Table II
General characteristics of clinical trials included in the selected studies
Clinical
trial
(author,
year)
Chia dosage
reported Design∕
follow-up Population
sex/age
Population profile
(Metabolic∕
pathological) Duration Diet∕Medications Statistics Outcomes of interest Principal findings
Vuksan
et al.
2007.
37 g/d ± 4 g
of milled chia
seed added to
white bread
Randomized,
placebo-
controlled,
single-blind
clinical
crossover trial
20
teenagers,
adults and
senior
citizens
of both
sexes.
Age:
18-75
Type-2 controlled
diabetics 12 weeks Diet: Recommended
by Canadian Diabetes
Association
Medication:
Individuals
maintained usual
treatment (type
and dosage) of oral
hypoglycemic,
antihypertensive
and antilipidemic
medication.
NCSS 2000
(NCSS
statistical
Software
Kaysville, UT)
Significance
p < 0.05
-Fasting blood glucose
and insulin
-Blood pressure (systolic
and diastolic)
-Lipids (Total, LDL,
HDL, TG)
Inflammatory markers
(CRP, fibrinogen,
Von Willebrand Factor
VIII).
Compared with
control group, chia
treatment lowered
SBP 6.3 ± 4.2 mmHg
(P < 0.001); CRP (mg/l)
40 ± 1.6% (P < 0.04);
Von Willebrand Factor
21 ± 0.3% (P < 0.03),
ALA and EPA increased
with chia consumption
(P < 0.05)
Vuksan
et al.
2010
0, 7, 15 or
24 g/d of chia
seed added to
white bread
Acute,
randomized,
placebo-
controlled,
double-blind
clinical
crossover
11 adults
of both
sexes
Age?
Healthy, eutrophic
individuals 120
minutes.
Capillary
blood
collection
15, 30, 60,
90 and 120
min. after
ingestion
Diet and medication
not reported NCSS 2000
(NCSS
statistical
Software
Kaysville, UT)
Significance
p < 0.05
Post-prandial blood
sugar Significant reduction
in post-prandial blood
sugar with all doses
(P = 0.002, r2 = 0.203)
Nieman
et al.
2009
25 g/d of chia
seed mixed
with 0.25 L of
water – twice
daily (50 g/d)
Randomized,
placebo-
controlled,
single-blind
clinical trial
76 adults
of both
sexes
Age: 20-
70 years
Healthy
individuals with
excess body fat
(≥ 25 Kg∕m2).
12 weeks Diet: individuals
oriented to maintain
standard diet
Medications: none
reported
T-Student test-
Significance
p < 0.05
Body composition and
mass, inflammatory
markers (CRP,
Interleukin-6, Monocyte-
Chemotactic Protein,
TNF Alpha); Oxidative
Stress Markers, PA;
Lipid Profile; Blood
glucose, analysis of fatty
acid in plasma
Compared to control
group, plasma ALA
increased 24.4%
(67.3 ± 5.6 to 83.7 ± 8.5
µg∕Ml)
P = 0.012
No significant difference
between groups in
reduction of body mass
or composition, blood
sugar, lipid profile, PA or
inflammatory markers
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cardiovascular risk factors in humans
Table II (cont.)
General characteristics of clinical trials included in the selected studies
Clinical
trial
(author,
year)
Chia dosage
reported Design∕
follow-up Population
sex/age
Population profile
(Metabolic∕
pathological) Duration Diet∕Medications Statistics Outcomes of interest Principal findings
Nieman
et al.
2012
25 g/d of
milled or
whole chia
seed
Randomized,
double-blind,
placebo-
controlled
clinical trial
56 adult
and
elderly
women;
Age 49-
79 years
Healthy with
excess body fat
(≥ 25 Kg∕m2),
post-menopausal,
non-smokers
10 weeks Diet: individuals
oriented to maintain
standard diet
Medications: none
reported
Anova
T-Student test
Mann-Whitney
test and
Wilcoxon test
MATLAB
R2010a
(MathWorks,
Inc., Natick,
MA)
Significance
p < 0.05
Body mass and
composition,
inflammatory markers
(PCR, Interleucine-6,
Monocyte
Chemoattractive Protein,
TNF Alpha); Oxidative
Stress Markers, PA;
Lipid Profile; Blood
glucose, analysis of fatty
acid in plasma
Significant increases in
serum concentrations
of ALA (58.4%
p = 0.002) and EPA
(38.6% p = 0.016) in
the group given milled
chia compared to that
given whole chia or
placebo. No significant
difference in body mass
or composition, blood
pressure, lipid profile or
inflammatory markers
between whole-seed,
milled or placebo
groups.
Jin
et al.
2012
25 g/day of
milled chia Individual, self-
reported clinical
trial. Six blood
extractions
10 women
Age 52-60
years
Post-menopausal,
healthy. BMI-17 to
29 Kg/m
7 weeks Diet: individuals
oriented to maintain
standard diet
Medications: none
reported
Anova
T-tests-
Bonferroni
Significance
p < 0.05
Plasma concentrations of
ALA , EPA and DHA No significant change
in body mass.(Pre-study
69.4 ± 13.8 Kg; three
weeks 69.3 ± 13.7 Kg;
seven weeks
60.1 ± 13.4 Kg) - p value
not mentioned
ALA - 138% increase
(p < 0.001)
EPA - 30% increase
(p = 0.019)
DHA-decrease (p=0.030)
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Table II (cont.)
General characteristics of clinical trials included in the selected studies
Clinical
trial
(author,
year)
Chia dosage
reported Design∕
follow-up Population
sex/age
Population profile
(Metabolic∕
pathological) Duration Diet∕Medications Statistics Outcomes of interest Principal findings
Guevara-
Cruz et
al. 2012
4 g of chia
seed mixed
with palm,
oats and
soy powder
diluted in
250 mL of
water/2 per
day
Randomized,
double-blind,
placebo-
controlled
clinical trial
67 adults
of both
sexes
Age 20-60
years
Individuals with
excess body mass
and metabolic
syndrome
2 months Diet: 500 kcal
reduction from usual
diet, reduction in
saturated fat and
cholesterol for
2 weeks before
randomization, and
after randomization
reduction of
500 kcal in diet and
further 235 kcal in
complement
Medications: none
reported
Kolmogorov-
Smirnov Z test
Anova
T-Student
Significance
p < 0.05
Body mass, waist
perimeter, body
composition, PA,
blood sugar, insulin,
lipid profile, leptin,
adiponectin, CRP
Significant decrease
in body mass and
composition, BMI and
waist circumference in
both groups (p < 0.0001).
Significant decrease
in TG (p = 0.05), CRP
(0.01) and insulin
resistance (0.001) only
in group with diet
+ complement. No
significant difference
found in blood sugar
or total plasma insulin,
cholesterol, HDL-c or
LDL-c in either group
(p > 0.05)
No change in leptin or
adiponectin.
Ho
et al.
2013
0, 7, 15 or
24 g of whole
or milled chia
added to white
bread
Acute,
randomized,
crossover
clinical trial
13
individuals
of both
sexes
Eutrophic, healthy
individuals Capillary
blood
collection
15, 30, 45,
60, 90 and
120 min
following
ingestion
Diet: not reported
Medications:
individuals using
blood sugar-
metabolization-
altering medications
excluded from study
Anova
NCSS 2000
(NCSS
statistical
Software
Kaysville, UT)
Significance
p < 0.05
Post-prandial blood
sugar represented
by area under curve
(IAUC))
Decrease in post-prandial
blood sugar significantly
related to dosage of chia
(p = 0.004); however, not
related to form—milled/
whole seed (p = 0.74)
when compared to
placebo group
PAS = systolic blood pressure, EPA = eicosapentaenoic acid, DHA = docosahexaenoic acid, BMI = body mass index, TG = triglycerides; CRP = C-reactive protein
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1915
Nutr Hosp. 2015;32(5):1909-1918Effects of chia consumption on
cardiovascular risk factors in humans
low-density lipoprotein (LDL-c), triglycerides (TG),
blood sugar, body mass, systolic and diastolic blood
pressure (SBP, DBP), inflammatory markers, and ALA
and EPA concentrations.
Data extraction
The data we extracted from the articles in our LRS
were: author and year of publication; how chia seed
was administered and dose; design\follow-up; study
population (sex\age); population profile (metabolic\
pathological); exposure\duration; diet\medications;
statistics, outcomes of interest, and principal findings.
(Table II).
Findings
Study selection
Figure 1 is a flowchart that describes the process of
selecting the studies. The search turned up 200 arti-
cles, of which 13 references were from Lilags, 98 from
Pubmed, six from Cochrane library, 17 from Scielo, 41
from Scopus, and 25 from Web of Science.
We made our initial selection based on title and abs-
tract, which were read by two reviewers independent-
ly of each other. Divergences between the reviewers
in selecting the studies were resolved by consensus.
Upon analyzing the inclusion and exclusion criteria,
seven studies were included in the LRS.
Description of studies in systematic review
Table II highlights the principal characteristics of
the studies included in our review. Sever articles pu-
blished between the years 2007 and 2013 met the in-
clusion criteria and were selected for the LRS. All the
studies are clinical trials, six are randomized (Vuksan
2007; Vuksan 2010; Nieman 2009; Nieman 2012;
Guevara-Cruz 2012; HO 2013), and five are place-
bo controlled (Vuksan 2007, Vuksan 2010, Nieman
2009, Nieman 2012, Guevara-Cruz 2012). Three of
the articles cover double-blind clinical trials (Vuksan
2007; Nieman 2012; Guevara-Cruz 2012), two are sin-
gle-blind, and three are crossover trials (Vuksan 2007;
Vuksan 2010; Ho 2013). Two of the studies are acute
trials (Vuksan 2010; HO 2013). In one of the studies
chia seed was added to other foods (Guevara-Cruz
2012).
The amount of the chia seed used in the different
studies varied from 4 to 50g, with some of the trials
using milled chia (Vuksan 2007; Jin 2012), while
others used whole chia seed (Vuksan 2010; Nieman
2009; Guevara-Cruz 2012) or both (Nieman 2012;
Ho 2013). In some of the studies, the chia, in either
whole or milled form, was added to bread (Vuksan
2007; Vuksan 2010; Ho 2013) or diluted in water
(Nieman 2009). In Guevara-Cruz et al.’s 2012 study,
the chia, along with palm, oats and soy protein, were
diluted in water. The studies where milled chia (Vuk-
san 2007; Nieman 2012; Jin 2012) was used obtained
the most positive results, as these found an associa-
tion with lowered blood sugar levels (Vuksan 2010;
Ho 2013).
Study-participant age varies from 18 to 79 years
of age. Sample size was a factor that varied a great
deal, with the smallest sample group composed of 10
individuals (Jin 2012), and the largest 76 (Nieman
2009). Study duration varied as well, the average be-
ing approximately 10 weeks.
The study populations’ metabolic profiles varied as
well, with one study involving people with type 2 dia-
betes (Vuksan et al. 2007), and another dealing with
metabolic syndrome (Guevara-Cruz et al. 2012). The
rest of the studies selected individuals showing no sig-
ns of disease, all of them being either healthy (Vuksan
et al. 2010; Jin et al. 2012; Ho et al. 2013) or overwei-
ght (Nieman et al. 2009; Nieman et al. 2012).
Only two of the studies involved dietary interven-
tion (Vuksan et al. 2007; Guevara-Cruz et al. 2012).
The findings from these are significant for outcomes
relating to CVD risk, such as SBP, inflammation mar-
ker (Vuksan et al. 2007), body mass, waist circumfe-
rence, body composition, TG and C-reactive protein
(CRP) (Guevara-Cruz et al. 2012; Jin et al. 2012). The
studies that did not involve dietary intervention (Nie-
man et al. 2009; Nieman et al. 2012; Jin et al. 2012)
and did maintain the dietary profile of the individual
participants, did not obtain results significant for said
outcomes. The acute trials (Vuksan 2010; Ho 2013)
sought to assess only post-prandial blood sugar levels
in relation to chia seed consumption.
The CVD-risk outcomes of interest assessed in the
studies varied. Although most of the outcomes were
not significant for such data as body mass, body com-
position, inflammatory markers, blood sugar, and li-
pid profile (Chart 2), there was consensus in regard to
the increase in ALA and EPA seen with chia ingestion
(Vuksan et al. 2007, Nieman et al. 2009, Nieman et al.
2012, Jin et al. 2012). The acute studies did not look at
ALA or EPA (Vuksan et al. 2010, Ho et al. 2013); only
at post-prandial blood sugar.
Cochrane Collaboration bias assessment
Cochrane Collaboration’s bias- or systematic er-
ror-assessment tool aims to determine whether a study
was executed properly, that is, without bias. For a
study to be valid one needs to determine whether the
design, data collection and analysis were done correct-
ly. Chart 3 shows the summarized bias risk according
to the authors regarding each of the articles in this LRS
selection. Graph 1 shows the bias risk for all the arti-
cles assessed.
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1916 Nutr Hosp. 2015;32(5):1909-1918 Cynthia de Souza Ferreira et al.
Six of the articles included (Table II) are randomi-
zed clinical trials, widely regarded as the gold standard
among all clinical research methods, as they are able
to produce direct scientific evidence with a low pro-
bability of error and thus shed light on a cause-effect
relationship between two events (de Carvalho 2013).
Though almost all the studies selected are said to
have included randomization, most of them were as-
sessed to have an unclear risk of bias for not providing
data as to how the randomization was conducted. The-
refore, we were unable to ascertainwhether there had
been any criteria for randomization that would mini-
mize the risk of bias.
As far as blinding of study participants, personnel
and outcome evaluators, there was a more homoge-
neous percentage between low and unclear risk of bias
in the studies (Fig. 1). One reason for this is the fact
that there was no report as to how the blinding was ob-
tained. It must be stressed that bias or systematic error
represents a flaw in the collection, analysis, interpreta-
tion, publication or review of data, leading to conclu-
sions that systematically tend to depart from the truth
(de Carvalho 2013). As most of the studies we looked
at were of unclear risk of bias for lack of information,
this risk seems inflated.
In regard to the reporting of selective outcomes,
the results described in both the studies by Nieman et
al. (2009 and 2012) showed high risk of bias. This is
because in these studies not all the primary outcomes
were reported, which may compromise the quality of
the study. In this respect the other studies were found
to have a low risk of bias.
Discussion
Most of the studies investigating chia seed con-
sumption, both by animals and humans, looked at the
effect on cardiovascular risk factors, excess body mass
and serum concentrations of ALA and EPA. The inte-
rest in this seed arose, mainly, due to its high levels of
ALA, fiber, proteins, minerals (calcium, magnesium
and potassium) and antioxidants (chlorogenic, caffeic,
quercetin and kaempeferolacids) (Norlaily 2012).
Although not common in studies on humans, some
research points to the consumption of chia having a
positive effect on health. However, these studies vary
a great deal in both sample size and the profiles of
the individuals in the sample group, which may have
created a discrepancy in the findings. Furthermore, the
quantities and forms of chia seed —ie, milled, who-
le-seed, baked in bread— were different in the diffe-
rent studies.
In Viksan et al.’s 2007 study, although it was one of
the few with significant findings (lowered blood pres-
sure and inflammatory markers) the sample size was
small (20 individuals) and the participants’ ages varied
from teenage to old age (18 to 75 years old). Hence,
having individuals in such distinct physiological con-
ditions may have affected the results, with no signi-
ficant difference found in lipid profile or body mass.
However, it was one of the few studies that took into
account the positive effect the nutritional intervention
had on the study outcomes.
Nieman et al. (2009) had the largest sample size in
their study (76 individuals of both sexes), but their se-
lection also had a broad age range, with both adults
and senior citizens (20-70 years old); they used chia
seed diluted in water, and their study had the largest
amount of chia (50g). There was no significant di-
fference in reduction of body mass or composition,
plasma lipoprotein concentrations, blood pressure or
inflammatory markers.
Nieman et al. (2012), so as to minimize the diffe-
rences between individuals, selected 56 women who
were healthy, post-menopausal (49-79 years old), non-
smokers and who consumed 25g of milled chia seed
per day. They noted a significant increase in serum
Table III
Summary of risk of bias. Review judgment by authors on each bias-risk item for each study in selection
Articles Other sources
of bias
Selective
outcome
reported
Incomplete
outcome Researcher
blinding Participant
blinding Allocation
concealment
Random-
sequence
generation
Vuksan 2007 + + + + + + +
Vuksan 2010 ? ? ? ? ? + ?
Nieman 2009 ? ? ? ? ? - ?
Nieman 2012 ? ? ? ? + - ?
Jin 2012 ? ? + + + + +
Guevar 2012 ? ? ? ? + + ?
Ho 2013 + ? + + + + ?
Key: + low risk
- high risk
? unclear risk
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1917
Nutr Hosp. 2015;32(5):1909-1918Effects of chia consumption on
cardiovascular risk factors in humans
Fig. 2.—Frequency of risk of
bias in studies assessed.
ALA and EPA levels in the group given milled chia,
but no change was found in the other study parameters.
The acute trials of Vuksan et al. (2010) and Ho et al.
(2013) involved a small number of individuals, 11 and
13 respectively, and used milled and/or whole-seed
chia to investigate only post-prandial blood sugar le-
vels. Both studies demonstrated chia seed to lower
blood sugar.
Jin et al. (2012) assessed 10 post-menopausal
women using 25g of milled chia per day over a se-
ven-week period, and found a significant increase in
serum ALA and EPA concentrations. Now, the study
by Guevara-Cruz et al. (2012), where they used a mix-
ture of palm, oats and soy powder diluted in 250 mL
of water in conjunction with a dietary intervention, de-
monstrated a significant decrease in body mass, BMI,
waist circumference, TG, CRP and insulin resistance.
In experimental studies, chia seed supplementation
attenuated metabolic, cardiovascular and hepatic al-
terations in rats subjected to a diet heavy in fat and
carbohydrates over an eight-week period. They noted
improved insulin sensitivity and glucose tolerance,
and a reduction in visceral fat, fatty liver and heart and
liver inflammation. No change was found in plasma
lipid concentrations or blood pressure (Poudyal 2012,
Chicco 2008). In another study on rats ingesting chia
seed, a significant drop was found in TG and LDL con-
centrations and a spike in HDL and polyunsaturated
fatty acids (Ayerza 2007).
All the studies show a certain risk of bias in some
respect, according to Cochrane Collaboration’s tool.
Mainly for the omission of details regarding study de-
sign, how the randomization and blinding was done,
and often the description of the outcomes proffered in
the study. Hence the quality of methodology in the stu-
dies on human chia consumption was compromised,
producing inconclusive results where the efficacy of
consuming chia to prevent/control cardiovascular risk
is concerned.
In spite of the many shortcomings of the studies
we selected, the strength of this LRS is the fact that
the research consists in two authors, independently of
each other, thoroughly searched six distinct databases.
This means there is a good likelihood that the all the
publications relating to the subject were identified and
included in the review. However, the findings are con-
tradictory, probably due to the methodological short-
comings identified in the selected studies.
Conclusion
The studies investigating the effect the consumption
of chia seed has on cardiovascular risk present incon-
clusive results. We underscore the need for randomi-
zed, double-blind, placebo-controlled clinical trials in
order to obtain results that are more reliable.
Conflict of interest
The authors declare that there is no conflict of in-
terest.
Acknowledgements
The authors thank the Eliana Rosa library for their
help in the bibliographic search.
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