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Effects of peanut processing on body weight and fasting plasma lipids

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Peanuts and peanut butter are commonly consumed as a snack, meal component and ingredient in various commercial products. Their consumption is associated with reduced CVD risk and they pose little threat to positive energy balance. However, questions have arisen as to whether product form (e.g. whole nut v. butter) and processing properties (e.g. roasting and adding flavours) may compromise their positive health effects. The present study investigated the effects of peanut form and processing on two CVD risk factors: fasting plasma lipids and body weight. One hundred and eighteen adults (forty-seven males and seventy-one females; age 29.2 (sd 8.4) years; BMI 30.0 (sd 4.5) kg/m2) from Brazil, Ghana and the United States were randomised to consume 56 g of raw unsalted (n 23), roasted unsalted (n 24), roasted salted (n 23) or honey roasted (n 24) peanuts, or peanut butter (n 24) daily for 4 weeks. Peanut form and processing did not differentially affect body weight or fasting plasma lipid responses in the total sample. However, HDL-cholesterol increased significantly at the group level, and total cholesterol, LDL-cholesterol and TAG concentrations decreased significantly in individuals classified as having elevated fasting plasma lipids compared with those with normal fasting plasma lipids. These observations suggest that the processing attributes assessed in this trial do not compromise the lipid-lowering effects of peanuts, and do not negatively impact body weight. Further studies are warranted to determine the effects of form and processing on other health risk factors.
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Effects of peanut processing on body weight and fasting plasma lipids
Fiona McKiernan
1
, Phoebe Lokko
2
, Anna Kuevi
2
, Regiane L. Sales
3
, Neuza M. B. Costa
3
, Josefina Bressan
3
,
Rita C. G. Alfenas
3
and Richard D. Mattes
1
*
1
Department of Foods and Nutrition, Purdue University, 212 Stone Hall, 700 West State Street, West Lafayette, IN, USA
2
CSIR-Food Research Institute, PO Box M20, Accra, Ghana
3
Department of Nutrition and Health, Federal University of Vic¸osa, Vic¸osa, MG 36570-000, Brazil
(Received 10 August 2009 – Revised 20 January 2010 – Accepted 3 February 2010 – First published online 11 May 2010)
Peanuts and peanut butter are commonly consumed as a snack, meal component and ingredient in various commercial products. Their consumption
is associated with reduced CVD risk and they pose little threat to positive energy balance. However, questions have arisen as to whether product
form (e.g. whole nut v. butter) and processing properties (e.g. roasting and adding flavours) may compromise their positive health effects. The
present study investigated the effects of peanut form and processing on two CVD risk factors: fasting plasma lipids and body weight. One hundred
and eighteen adults (forty-seven males and seventy-one females; age 29·2 (SD 8·4) years; BMI 30·0 (SD 4·5) kg/m
2
) from Brazil, Ghana and the
United States were randomised to consume 56 g of raw unsalted (n23), roasted unsalted (n24), roasted salted (n23) or honey roasted (n24)
peanuts, or peanut butter (n24) daily for 4 weeks. Peanut form and processing did not differentially affect body weight or fasting plasma
lipid responses in the total sample. However, HDL-cholesterol increased significantly at the group level, and total cholesterol, LDL-cholesterol
and TAG concentrations decreased significantly in individuals classified as having elevated fasting plasma lipids compared with those with
normal fasting plasma lipids. These observations suggest that the processing attributes assessed in this trial do not compromise the lipid-lowering
effects of peanuts, and do not negatively impact body weight. Further studies are warranted to determine the effects of form and processing on
other health risk factors.
Peanuts: Peanut butter: Processing: Plasma lipids: Body weight
CVD is the leading cause of death in the USA, accounting for
one in every 2·8 deaths
(1)
. With an ageing population, the
prevalence is predicted to double by 2050
(2)
. CVD is also
expected to have an increasing detrimental effect in other
nations throughout the world
(3)
. Rates of CVD and stroke
are projected to triple in Latin America and sub-Saharan
Africa in the next two decades
(3)
.
Peanuts and tree nuts are increasingly recognised for their
role in CVD risk reduction, as acknowledged by a Food
and Drug Administration qualified health claim in 2003
(4)
.
Epidemiological studies estimate an approximate 35 % reduc-
tion in the incidence of CVD in the highest nut-consuming
groups
(5 – 8)
. Multiple components of peanuts including
arginine, folate, tocopherols and fatty acids probably mediate
their cardioprotective effects.
Clinical studies indicate that tree nuts, with most of
the evidence derived from almonds and walnuts, reduce
LDL-cholesterol (LDL-C) by 3 – 19 % compared with refer-
ence diets, including habitual, lower fat and average American
diets
(9)
. Reductions of up to 11 % in total cholesterol and
14 % in LDL-C have been reported for peanut interventions
compared with similar reference diets
(10– 12)
.Consistentwitha
more general literature
(13– 16)
, the degree of reduction in plasma
cholesterol concentrations in response to peanut consumption
is inversely related to baseline concentrations
(11)
.
While promoting improved lipid profiles, nut consumption
has limited impact on body weight
(17)
. Epidemiological
studies reveal either a negative association or a lack of associ-
ation between nut consumption and BMI
(5 – 7)
. Clinical studies
support a lack of association under a variety of conditions
(17)
,
and may actually aid weight loss through improved dietary
compliance
(18)
. Because central obesity is an independent
risk factor for CVD, and weight loss leads to a reduction in
disease risk
(19)
, moderate consumption of nuts may be a func-
tional component in a cardioprotective diet
(20)
.
Clinical intervention studies exploring the effects of nuts on
CVD risk and body weight have used natural, unprocessed nuts;
lightly salted, roasted nuts; or an unspecified nut variety. Since
numerous flavours and forms of nuts are currently available on
the market, questions have arisen as to whether processing
properties (e.g. grinding to butter, roasting and boiling) and
the addition of flavours (e.g. salt, spices and sugar) may alter
the health effects
(21)
. For example, grinding nuts into butter
form ruptures the parenchymal cell walls that encapsulate the
intracellular components
(22)
. While the complete effects of
this alteration in nut form remain unknown, it results in signifi-
cantly less faecal fat, protein and tocopherol losses compared
with the whole nut form
(23,24)
. Furthermore, concerns have
arisen as to the possible adverse effects of the addition
of hydrogenated oils to peanuts to prolong shelf life.
*Corresponding author: Richard D. Mattes, fax þ1 765 494 0674, email mattes@purdue.edu
Abbreviations: HDL-C, HDL-cholesterol; LDL-C, LDL-cholesterol.
British Journal of Nutrition (2010), 104, 418–426 doi:10.1017/S0007114510000590
qThe Authors 2010
British Journal of Nutrition
Because hydrogenated fats are potential sources of trans fats,
which have detrimental effects on plasma lipids and CVD
risk
(25,26)
, the addition of hydrogenated fats during processing
could compromise the cardiovascular health benefits associated
with nut consumption. Analyses of common peanut butter
brands reveal non-detectable levels of trans fats in the brands
analysed
(27)
, but concerns persist. Limited evidence also
indicates that the modification of rheological properties
during processing may alter the satiety properties of nuts
(28)
with possible implications for energy balance.
The primary aim of the present study was to determine
whether the form, flavour and processing of peanuts alter
the fasting plasma lipid profile and body weight response to
their consumption over a 1-month intervention period. Peanuts
were used as the test nut as they are the most commonly
consumed nut (actually a legume) in the USA, and are avail-
able in many flavours and forms
(29)
. Based on evidence that
greater effects may be observed in individuals with the great-
est baseline cholesterol concentrations, differential responses
between normolipidaemic and hyperlipidaemic individuals
were explored.
Methods
Participants
A total of 120 participants from three countries (Brazil, Ghana
and the USA) participated in this multi-centre trial. Forty
participants were recruited at each site. Eligibility criteria
included stable weight (no deviations .2·5 kg over the prior
3 months); BMI $25 kg/m
2
; pre-menopausal; having no
known lipid disorders or other acute or chronic diseases;
using no prescription medications apart from birth control;
and having no nut allergies. The final sample included
118 participants (forty-seven males and seventy-one females;
age 29·2 (SD 8·4) years; BMI 30·0 (SD 4·5) kg/m
2
; Table 1),
as the final outcome measures from two participants in
Ghana were not available for analyses. The present study
was conducted according to the guidelines laid down in the
Declaration of Helsinki, and all procedures involving human
subjects/patients were approved by human research review
boards at each location. Written informed consent was
obtained from all the subjects/patients.
Experimental design
The study used a parallel group experimental design. Partici-
pants were sequentially assigned to incorporate 56 g (2 oz)
of one of five peanut forms into their diet daily for 4 weeks.
Each country distributed the participants into five groups
with eight people per group. The five peanut forms were
whole raw unsalted, whole roasted unsalted, whole roasted
salted, whole honey roasted peanuts, and peanut butter. The
daily energy and nutrient composition of each treatment are
presented in Table 2. Participants were allowed to consume
the peanuts/peanut butter at any time of the day and in any
manner they chose, but they were requested to restrict con-
sumption of all other nut products during the intervention
period. No additional dietary instructions were provided.
To ensure consistency across the research sites, all peanuts
and peanut butter were provided by a single site (USA).
Participants collected their daily peanut rations at the research
site, pre-weighed and labelled, on a weekly basis.
Anthropometrics
After a 10 h overnight fast and after voiding, body weight was
measured (^0·1 kg) using calibrated scales (model TBF-305;
Tanita, Arlington Heights, IL, USA), with participants
wearing no shoes and a light gown, at baseline and post treat-
ment (week 4). Standing height was measured (^0·1 cm)
using a wall-mounted stadiometer (Holtain Limited, Crymych,
Dyfed, UK). To allow sub-group analyses, participants
were classified, according to BMI, into overweight (BMI
25 –29·9 kg/m
2
;n72) and obese (BMI $30 kg/m
2
;n46)
categories. Participants were requested to maintain their
customary activity levels during the study period, so any
changes in body weight were presumed to be due to the
dietary intervention.
Fasting plasma lipids
After a 10 h overnight fast, 6 ml of blood were collected at
baseline and post-treatment into vacutainers containing
EDTA. The samples were immediately placed on ice, and
were then centrifuged (3000 rpm £15 min at 4 8C), separated
and stored at 280 8C until analyses. Samples were analysed
Table 1. Age, weight and BMI, and the distribution of participants based on lipids for the total group and by country at baseline
(Mean values and standard deviations)
Total Brazil Ghana USA
nMean SD nMean SD nMean SD nMean SD
Age (years) 29 8 32
a
10 29
a,b
627
b
8
Weight (kg) 85 15 82
a,b
16 82
a
13 90
b
16
Weight change (kg) 0·3 0·1 0·6 0·3 0·5 0·0 0 0·1
BMI (kg/m
2
) 30 4 29 4 31 5 30 4
Total cholesterol ,2000 mg/l 85 25 30 30
Total cholesterol $2000 mg/l 33 15 8 10
LDL-C ,1300 mg/l 99 27 36 36
LDL-C $1300 mg/l 19 13 2 4
TAG ,1500 mg/l 92 24 36 32
TAG $2000 mg/l 26 16 2 8
LDL-C, LDL-cholestrol.
a,b
Mean values for age and weight within a row with unlike superscript letters were significantly different from each other (P,0·05).
Peanut processing and CVD risk 419
British Journal of Nutrition
in duplicate for total cholesterol, LDL-C, HDL-cholesterol
(HDL-C) and TAG concentrations using an automated clinical
chemistry analyser (COBAS Integra 400, Roche Diagnostic
Systems, Branchburg, NJ, USA).
The ratios of total cholesterol to HDL-C, HDL-C to LDL-C
and TAG to HDL-C were calculated based on evidence that
the ratios of these lipids may be more important and more
robust predictors of CVD risk than any lipid fraction
alone
(30,31)
.
Due to evidence indicating that plasma lipid responses to
cholesterol-lowering interventions may be greatest in indivi-
duals with the highest baseline lipid concentrations
(11)
, partici-
pants were categorised based on baseline total cholesterol,
LDL-C and TAG concentrations to allow sub-group analyses.
The total cholesterol groups were classified as normal
(total cholesterol concentrations ,2000 mg/l; n85) or high
(total cholesterol concentrations $2000 mg/l; n33); LDL-C
groups as normal (LDL-C concentrations ,1300 mg/l; n100)
or high (LDL-C concentrations $1300 mg/l; n18); and TAG
groups as normal (TAG concentrations ,1500 mg/l; n92) or
high (TAG concentrations $1500 mg/l; n26)
(32)
.
Dietary intake
Three-day food records (two non-consecutive weekdays and
one weekend day) were recorded at baseline and during
weeks 2 and 4 of the intervention. Training was provided on
the method for estimating food portion sizes using food
models. Food records were reviewed with participants once
they were completed to clarify details and obtain any
additional information deemed necessary. Each study site ana-
lysed the food records using country-specific nutrient data-
bases, focusing specifically on the daily intake of energy,
total fat, carbohydrate and protein. In addition, US food
records were analysed for SFA, MUFA, PUFA, cholesterol,
total dietary fibre, soluble fibre, insoluble fibre, total a-toco-
pherol, folate, Mg and arginine.
Peanut form palatability
At baseline and post treatment, each of the five peanut forms,
weighing between 1·38 and 1·42g, was sampled in a random-
ised order and rated for palatability on a hedonic scale end
anchored with ‘not at all palatable’ and ‘extremely palatable’.
Participants rinsed thoroughly between samples. The mean
palatability of the peanut form consumed daily during the
intervention period was compared with the mean palatability
of the other four non-intervention peanut forms to assess the
impact of frequency of consumption on palatability ratings.
Appetite ratings
An additional component of the US study required participants
to record the subjective sensations of hunger, fullness, desire
to eat, desire to eat something sweet, desire to eat something
salty, prospective consumption and thirst on visual analogue
scales (developed by W. Horn) on personal digital assistants.
The scales were end anchored with ‘not at all’ and ‘extre-
mely’. Each scale was completed every waking hour for
24 h during one weekday of baseline and weeks 2 and 4 of
the intervention. The day of the week on which the recordings
were made was held constant for each participant.
Statistical analyses
Statistical analyses were performed using SPSS (version 16.0,
SPSS Inc., Chicago, IL, USA). Treatment effects were tested
by repeated-measures ANOVA, with time as the within-sub-
ject factor and peanut form as the between-subject factor.
Country was not entered as a between-subject factor in the
final analyses because there were no significant differences
between them with respect to the main outcome variables.
Sub-group analyses were conducted for sex, BMI and lipid
categories using the grouping variable as the between-subject
factor in a repeated-measures ANOVA and time as the within-
subject factor. Paired ttests were performed for post hoc ana-
lyses with the Bonferroni adjustment when the main effects
were significant. A significance level of P,0·05, two-tailed,
was set as the criterion for significance. All data are expressed
as mean values and standard deviations.
Results
Body weight/BMI and sex
Independent sample ttests revealed no statistically significant
BMI/body weight or sex effects within any of the groups for
the main outcome measures. There were no significant differ-
ences between peanut form groups at baseline with respect to
body weight (84·6 (SD 15·2) kg). There was also no significant
time or time £peanut form interaction with respect to change
in body weight following the intervention. Mean body weight
at the end of week 4 was 84·9 (SD 15·1) kg.
Table 2. Mean energy and nutrient composition of 56 g of raw unsalted, roasted unsalted and roasted salted,
honey roasted peanuts, and peanut butter
Raw Roasted unsalted Roasted salted Honey roasted Peanut butter
Energy (kJ) 1329 1403 1403 1308 1378
Energy (kcal) 318 335 335 313 329
Total fat (g) 27·6 29·4 29·4 25·5 28·2
Saturated fat (g) 3·8 4·9 4·9 4·2 5·8
MUFA (g) 13·7 14·5 14·5 12·6 13·3
PUFA (g) 8·7 8·6 8·6 7·4 7·8
Carbohydrate (g) 9·0 8·6 8·6 13·3 11·0
Dietary fibre (g) 4·8 5·3 5·3 4·6 3·4
Protein (g) 14·5 15·7 15·7 13·6 14·1
F. McKiernan et al.420
British Journal of Nutrition
Dietary intake
Total daily energy intake did not change significantly between
baseline and post treatment (Fig. 1). Total fat intake increased
significantly (F(1,112) ¼41·6, P,0·01), carbohydrate intake
decreased significantly (F(1,112) ¼12·7, P,0·01) and protein
intake increased significantly (F(1,112) ¼5·9, P¼0·02) from
baseline (Fig. 1). There were no significant differences
between the peanut form groups with respect to changes in
total daily energy intake or intake of the macronutrients.
In the US sample, there were significant increases in MUFA
(F(1,35) ¼26·1, P,0·01), PUFA (F(1,35) ¼6·5, P¼0·02),
fibre (F(1,35) ¼13·4, P,0·01), folate (F(1,35) ¼13·7,
P,0·01) and arginine (F(1,35) ¼22·8, P,0·01) intakes rela-
tive to baseline (Table 3). There was a trend towards a signifi-
cant increase in total a-tocopherol, but this just failed to reach
statistical significance (F(1,35) ¼3·9, P¼0·06). There was no
significant change in SFA intake.
Plasma lipids
Baseline measurements of total cholesterol were significantly
higher in the roasted unsalted group than in the peanut
butter group (P¼0·01; Table 4). There were no significant
differences in LDL-C, HDL-C or TAG concentrations at base-
line between treatment groups. Furthermore, baseline
measurements of total cholesterol:HDL-C, HDL-C:LDL-C
and TAG:HDL-C ratios did not differ significantly between
peanut form treatment groups.
In the full sample, total cholesterol and LDL-C concen-
trations did not change significantly from baseline to post
treatment (Table 4). HDL-C concentrations increased signifi-
cantly from baseline (F(1,113) ¼6·9, P¼0·01). Mean serum
TAG concentrations decreased by 5 % from baseline to post
treatment, but these failed to reach statistical significance
(F(1,113) ¼1·6, P¼0·21). The total cholesterol:HDL-C ratio
did not change significantly from baseline to post treatment.
There was a trend towards an increase in the HDL-C:LDL-C
ratio (F(1,113) ¼2·8, P¼0·097). The TAG:HDL-C ratio
decreased significantly from baseline to post treatment
(F(1,113) ¼4·1, P¼0·04).
There were no significant differences between peanut form
treatment groups with respect to changes in total cholesterol,
LDL-C, HDL-C or TAG concentrations. No significant treat-
ment group differences were noted in the change in total cho-
lesterol:HDL-C, HDL-C:LDL-C or TAG:HDL-C ratios.
Sub-group analyses revealed a significant time £lipid cat-
egory interaction for total cholesterol and LDL-C concen-
trations (Fig. 2). Individuals in the high total cholesterol
group ($2000 mg/l) had significantly greater decreases of
total cholesterol and LDL-C concentrations than individuals
in the normal total cholesterol group (F(1,116) ¼6·6,
P¼0·01 and F(1,116) ¼6·2, P¼0·02, respectively). Individ-
uals with high LDL-C concentrations had significantly greater
decreases of total cholesterol and LDL-C concentrations
than individuals with normal LDL-C concentrations
(F(1,116) ¼13·9, P,0·001 and F(1,116) ¼14·1, P,0·001,
800
400
0
–400
Total
energy
Fat Protein
Carbohydrate
–800
Change from baseline (kJ/d)
*
*
*
Fig. 1. Changes in daily total energy and macronutrient intakes (as kJ/d)
from baseline for the total group (n118). Values were represented ass
means and standard deviations. * Mean values were significantly different
from baseline (P,0·05).
Table 3. Total daily energy and nutrient intakes at baseline and post treatment for the US sample only (n40)
(Mean values and standard deviations)
Baseline Post treatment
Mean SD Mean SD P
Total daily energy (kJ/d) 8426 2478 8468 1901 0·681
Total daily energy (kcal/d) 2014 592 2024 454 0·681
Total fat (g/d) 78 32 88* 25 0·005
Saturated fat (g/d) 27 12 27 9 0·287
MUFA (g/d) 29 12 36* 10 ,0·01
PUFA (g/d) 16 8 19* 7 0·015
Cholesterol (mg/d) 230 153 217 135 0.496
Carbohydrate (g/d) 250 75 229* 63 0·029
Total dietary fibre (g/d) 17 5 18 5 0·059
Soluble dietary fibre (g/d) 4·7 1·7 4·3 1·3 0·253
Insoluble dietary fibre (g/d) 11·7 4·1 13·5* 4·1 ,0·001
Total protein (g/d) 82 27 86 26 0·186
Total a-tocopherol (mg) 12·1 11·7 14·3 13·9 0·057
Natural folate (mg/d) 199 84 242* 85 0·001
Mg (mg/d) 285 104 319* 82 0·022
Arginine (g/d) 4·3 1·7 5·3* 1·7 ,0·001
* Mean values were significantly different from baseline (P,0·05).
Peanut processing and CVD risk 421
British Journal of Nutrition
respectively). Individuals with elevated baseline TAG concen-
trations had significantly greater decreases of TAG concentrations
relative to individuals with normal TAG concentrations
(F(1,116) ¼9·6, P,0·01).
The lipid subgroups did not differ significantly with respect
to baseline body weight, change in body weight, or change in
total daily energy, protein, fat or carbohydrate intake. How-
ever, the individuals classified as having high total cholesterol
were significantly older than individuals with normal total
cholesterol (28 (SD 7) and 33 (SD 10) years, respectively,
P,0·05). Similarly, individuals classified as having high
LDL-C concentrations were significantly older than individ-
uals with normal LDL-C concentrations (28 (SD 7) and 34
(SD 11) years, respectively, P,0·05).
Appetite ratings
Self-reported hunger, fullness, desire to eat, desire to eat
something sweet or salty, prospective consumption and thirst
ratings did not change significantly with time. Furthermore,
there was no time £peanut form interaction for any of these
variables.
Peanut form palatability
While peanut butter was rated as the most palatable (78 (SD
20)) form and raw peanuts were rated as the least palatable
(34 (SD 24)) form, there were no significant differences in
palatability between the nut treatments at baseline. Honey
roasted, roasted salted and roasted unsalted peanuts were
rated at 75 (SD 22), 73 (SD 15) and 60 (SD 18), respectively.
The palatability ratings of the nuts consumed daily during
the intervention decreased with time, but not significantly
(mean rating at baseline: 70 (SD 23); mean rating post treat-
ment: 65 (SD 25)). Furthermore, there was no significant
time £peanut form interaction for this variable. The rate of
change in palatability ratings was not significantly different
between the nuts consumed daily during the intervention and
the other four nuts that were not consumed daily.
Discussion
Epidemiological and clinical evidence support a beneficial
effect of nut consumption on CVD risk factors, in particular
plasma lipid concentrations
(8,9,33)
. Benefits are achieved
while having a limited impact on body weight
(17)
. However,
the evidence supporting this association is mainly derived
from unprocessed nuts, and changes introduced during proces-
sing have been hypothesised to alter these findings
(21)
. The
present study suggests that processing, specifically the
addition of flavours, grinding to butter and roasting, does
not alter the lipid-lowering effects of peanuts. Significant
lipid-lowering effects were observed in hyperlipidaemic indi-
viduals with all peanut varieties. Furthermore, these benefits
were achieved without altering body weight status.
In the present study, significant reductions in total choles-
terol, LDL-C and TAG concentrations were observed when
hyperlipidaemic individuals consumed 56 g of whole raw,
roasted unsalted, roasted salted or honey roasted peanuts, or
ground peanut butter daily for 4 weeks. There were no signifi-
cant differences between the peanut treatments with respect
to these lipid-lowering responses despite differences in
Table 4. Serum lipid concentrations at baseline and post treatment by nut treatment group
(Mean values and standard deviations)
Baseline Post treatment
Serum lipid Nut treatment nMean SD Mean SD P
Total cholesterol (mg/l) Honey roasted 24 1810
a,b
360 1780
a,b
300
Roasted salted 23 1820
a,b
250 1840
a,b
240
Raw 23 1770
a,b
300 1840
a,b
360
Roasted unsalted 24 2030
a
460 2010
a
380
Peanut butter 24 1720
b
230 1750
b
250
Total 118 1830 340 1840 320 0·573
LDL-cholesterol (mg/l) Honey roasted 24 1040 280 1010 240
Roasted salted 23 1050 240 1060 250
Raw 23 1040 260 1050 260
Roasted unsalted 24 1190 400 1170 360
Peanut butter 24 990 200 1030 230
Total 118 1060 290 1060 280 0·887
HDL-cholesterol (mg/l) Honey roasted 24 510 160 530 180
Roasted salted 23 530 160 560 180
Raw 23 520 160 540 200
Roasted unsalted 24 610 220 630 240
Peanut butter 24 490 120 510 120
Total 118 530 170 560* 190 0·009
TAG (mg/l) Honey roasted 24 1330 730 1220 680
Roasted salted 23 1120 690 1100 730
Raw 23 1080 420 1190 530
Roasted unsalted 24 1170 620 1060 480
Peanut butter 24 1120 540 980 460
Total 118 1160 610 1110 580 0·197
a,b
Mean values within a column with unlike superscript letters were significantly different from each other and lipid category (P,0·05).
* Mean values were significantly different from baseline (P,0·05).
F. McKiernan et al.422
British Journal of Nutrition
processing such as grinding and roasting before consumption.
Overall, total cholesterol decreased by 3 % (74 mg/l), LDL-C
decreased by 10 % (150 mg/l) and TAG concentrations decrea-
sed by 13 % (290 mg/l) from baseline. O’Byrne et al.
(10)
reported greater reductions in total cholesterol and LDL-C
in hyperlipidaemic women following peanut consumption,
with concentrations decreasing by 10 and 12 %, respectively.
However, the peanuts used in that study were enriched
with oleic acid, containing 60 –70 % more than other
commercially available varieties of peanuts. Also differences
in the contribution of dietary SFA to total daily energy
intake may account for the disparities in the reported choles-
terol-lowering effects. In the study by O’ Byrne et al.
(10)
,
SFA contributed 5 % to total energy intake in contrast to
12 % in the present study. Since a direct, positive, dose-
dependent relationship exists between SFA and plasma total
cholesterol and LDL-C
(20)
, the differences in dietary SFA
likely account, at least partially, for the differences observed.
The cholesterol-lowering effects in the present study are,
thus, predicted to be even greater if accompanied by a lower
SFA diet.
While the unsaturated fatty acid profile of nuts (high MUFA
and PUFA) is thought to mediate the majority of the favour-
able effects on plasma lipids, other components such as fibre
and phytosterols may also contribute
(8,9)
. Furthermore, in the
present study, the lower TAG concentration may stem from
the spontaneous reduction in carbohydrate intake when the
peanuts were added to the diet. Reductions in carbohydrate
intake are associated with decreases in TAG concen-
trations
(34)
, and thus, the decreases in carbohydrate intake
reported may have had an independent effect on lipid concen-
trations. It is estimated that a 370 mg/l (1 mmol/l) reduction in
total cholesterol and LDL-C results in 24 – 28 % decreases in
the relative risk of CHD mortality
(35)
, and that an 880 mg/l
(1·0 mmol/l) decrease in TAG is associated with a 14 –37 %
reduction in overall CVD risk
(36)
.
In contrast to the hyperlipidaemic individuals, no significant
changes in plasma lipids were observed in the individuals with
normal lipid concentrations. This is in contrast to a peanut
intervention study that reported a 12 % reduction in total
cholesterol and a 10 % reduction in LDL-C in normocholester-
olaemic individuals consuming whole peanuts and peanut
butter for 24 d
(11)
. In that study, MUFA from peanuts were
substituted for SFA, resulting in a decrease in the contribution
of SFA to the total daily energy intake from 16 to 7 % during
the peanut intervention
(11)
. However, in the present study, no
substitutions were made, and SFA intake levels did not change
from baseline and were maintained at 12 % of total daily
energy intake during the intervention. A similar study also
failed to report significant changes in total cholesterol or
LDL-C following a peanut intervention trial in normocholes-
terolaemic individuals when the contribution of SFA to the
diet remained relatively stable at 10 % of total daily energy
intake
(37)
. These findings indicate that a simultaneous
reduction in SFA and an increase in MUFA may be necessary
to elicit changes in plasma lipids in normolipidaemic individ-
uals with peanut consumption. However, of note, the
reductions observed by Kris-Etherton et al.
(11)
among
normocholesterolaemic individuals were greater in those
with the highest concentrations at baseline. This is consistent
with the present findings and with several reports from
other lipid-lowering dietary interventions with foods such
as oats
(13 – 16)
.
The present study supports the findings from epidemiologi-
cal and clinical studies reporting that peanut consumption has
limited effects on body weight
(5,6,10,12,38,39)
. However, the
results extend beyond these findings to indicate that neither
peanut form nor flavour affects this outcome measure. Con-
sumption of four different flavours of whole peanuts or
100
(a)
(b)
(c)
50
0
–50
Total
(
n
118)
Normal Total-C
(
n
85)
(<2000 mg/l)
High Total-C
(
n
33)
(2000 mg/l)
*
–100
Change from baseline in
Total-C (mg/l)
100
50
0
–50
Total
(
n
118)
Normal LDL-C
(
n
100)
(<1300 mg/l)
High LDL-C
(
n
18)
(1300 mg/l)
*
–200
–100
–150
Change from baseline in
LDL-C (mg/l)
100
0
Total
(
n
118)
Normal TAG
(
n
92)
(<1500 mg/l)
High TAG
(
n
26)
(1500 mg/l)
*
–600
–100
–200
–300
–400
–500
Change from baseline in
TAG (mg/l)
Fig. 2. Changes in (a) total cholesterol (Total-C), (b) LDL-cholesterol
(LDL-C) and (c) TAG from baseline for the total group and according to lipid
subgroups. Values were represented ass means and standard deviations.
(a) * Mean values were significantly different from normal Total-C group
(P,0·05). (b) * Mean values were significantly different from normal LDL-C
group (P,0·05). (c) * Mean values were significantly different from normal
TAG group (P,0·05).
Peanut processing and CVD risk 423
British Journal of Nutrition
peanut butter at a level of approximately 1363·9 kJ/d (mean
daily energy contributed from the five peanut treatments) for
4 weeks did not cause any significant changes in body
weight. The mean theoretical weight gain due to the peanut
intervention was calculated to be 1·2 kg over the 4-week
period assuming no compensation. As the mean change in
body weight was 0·3 (SD 0·1) kg, a strong compensation for
the peanut energy load is indicated. The lack of effect on
body weight could be due to dietary compensation and
increased satiety, limited efficiency of absorption of energy
from the peanuts or increased energy expenditure
(17)
.
Beneficial changes in dietary intake beyond MUFA and
PUFA intakes were observed in the present study, as reflected
by the US food intake records. Arginine, folate and Mg intakes
increased significantly. Since arginine is the precursor of NO,
which has many bioactive properties, including vasodilation
and reduced platelet aggregation
(40)
, increases in dietary
intake may contribute to cardioprotective effects beyond
those associated with lipid-lowering. Increasing folate intake
may also improve plasma homocysteine status
(41)
. Elevated
homocysteine concentrations are an independent risk factor
for the development of atherosclerosis
(42)
, and thus, by func-
tioning as a methyl donor in the conversion of homocysteine
to methionine, dietary folate can lower plasma homocysteine
concentrations and lower CVD risk
(41)
. Increases in Mg
intake may afford additional benefits if they translate into
increases in plasma Mg concentrations, as the risk of CVD
is inversely related to the concentration of plasma Mg
(43,44)
.
The potential mechanisms mediating this beneficial outcome
include a reduction in the formation of free oxygen radicals
and pro-inflammatory molecules
(44)
. Furthermore, while
a-tocopherol intakes only tended to rise, its antioxidant prop-
erties, along with those of other antioxidants in nuts, are
hypothesised to reduce atherogenic oxidative processes
(45,46)
.
A reduction in lipid peroxidation has been noted with
peanut consumption
(47)
, and improvements in oxidative
markers have also been documented for other nuts
(48,49)
.
The increases in intake of cardioprotective nutrients other
than MUFA and PUFA noted in the present study are similar
to those reported previously
(37)
.
While the present study failed to observe an effect of pro-
cessing on the lipid-lowering effects of peanuts, future studies
are warranted to determine the impact of processing on other
CVD risk parameters such as blood pressure, oxidative stress,
inflammation, insulin sensitivity and endothelial function. It is
plausible that the lipid-lowering effects are maintained, but the
overall health effects are altered. Furthermore, while the pre-
sent research suggests that the addition of salt and sugar,
grinding to butter and roasting do not have implications for
the short-term lipid-lowering effects of peanuts, the effects
of other processing procedures on health outcomes merit
investigation, e.g. boiling of peanuts and removal of skin.
Boiling of peanuts in water could lead to the leaching out of
cardioprotective, water-soluble nutrients
(50)
, while removal
of the skins of peanuts during processing significantly alters
the antioxidant capacity
(51)
. The effects of processing on
other nut varieties also warrant exploration.
Similar to previous reports
(52,53)
, the present study noted a
decrease in palatability ratings over time. However, the hedo-
nic ratings were not significantly different at the end of the
intervention compared with baseline. Thus, while a degree
of monotony occurred, it was not significant. Alper &
Mattes
(39)
reported a similar stability of palatability ratings
with daily consumption of peanuts for 8 weeks. This indicates
a tolerance of daily nut consumption. Furthermore, given the
comparable health effects noted with the different peanut
forms, varying the sensory properties may aid regular use
without compromising the benefits.
Failure to measure compliance by an objective measure
such as changes in erythrocyte membrane fatty acid compo-
sition is a limitation of the present research. Furthermore,
while food intake diaries are frequently used to estimate
food intake in free-living individuals, they are not without
error. This technique has been shown to underestimate intakes,
especially in obese individuals
(54)
. And while measures were
taken to improve accuracy (e.g. participants received edu-
cation on how to record food intake accurately, and records
were reviewed for accuracy with participants), the mean
daily energy intakes were more reflective of the energy
needs of a normal weight population (approximately
8368 kJ/d) than of those of the present overweight population.
Conclusions
Different forms and flavours of peanuts, when consumed in
moderate quantities, lead to a less atherogenic lipid profile
in hyperlipidaemic individuals. Such changes may be achieved
without significant impact on body weight. The continued
high palatability of the peanuts over the trial period suggests
that monotony will not be a barrier to regular consumption.
The lack of significant country effects also indicates that nut
consumption may be a feasible intervention to reduce CVD
risk globally.
Acknowledgements
We thank the assistance of William Horn for the development
and adaptation of the Appetite Log VAS software (US Depart-
ment of Agriculture, Agricultural Research Service, Western
Human Nutrition Research Center, Davis, CA 95 616, USA).
None of the authors have a conflict of interest related to this
work of manuscript. R. D. M. contributed to the design and anal-
ysis of the study and manuscript preparation, and had primary
responsibility for its final content. F. M. contributed to the
design, conduct and analysis of the study and manuscript
preparation. P. L., A. K., R. L. S., N. M. B. C., J. B. and R. C.
G. A. contributed to the conduct and analysis of the study as
well as to the manuscript preparation. This research was sup-
ported by a grant from the US Agency for International Devel-
opment Peanut Collaborative Research Support Program
#RD309-022/4092094 and FAPEMIG APQ-0957-4.08/07.
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... As one of the most affordable and abundant types of nut available on the market, peanuts are culturally acceptable in many parts of the world, including in China (17). Few clinical trials have shown favorable metabolic effects of peanut consumption on single risk factors among participants with overweight/obesity (18)(19)(20), dyslipidemia (21,22), or T2D (23,24). However, there is limited evidence on the effects of peanuts on hyperglycemia or dyslipidemia among individuals with MetS or at risk of MetS. ...
... Inconsistent results have also been reported for studies that examined the effects of peanuts on lipid parameters. Among these, some trials have reported that peanut consumption increases HDL cholesterol (20,21) and/or decreases triglycerides (20,22,32), LDL cholesterol (20), or total cholesterol (20,22) within or between groups, whereas other studies have reported null findings (21)(22)(23)(24)32). These discrepancies among studies may be attributed to relatively small sample sizes (ranging from 25 to 151), differences in participant characteristics, study design (peanut dose, intervention duration, and control foods), and habitual background dietary patterns. ...
... Inconsistent results have also been reported for studies that examined the effects of peanuts on lipid parameters. Among these, some trials have reported that peanut consumption increases HDL cholesterol (20,21) and/or decreases triglycerides (20,22,32), LDL cholesterol (20), or total cholesterol (20,22) within or between groups, whereas other studies have reported null findings (21)(22)(23)(24)32). These discrepancies among studies may be attributed to relatively small sample sizes (ranging from 25 to 151), differences in participant characteristics, study design (peanut dose, intervention duration, and control foods), and habitual background dietary patterns. ...
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Purpose of Review To summarize recent evidence from randomized controlled feeding trials (RCTs) on the effects of consuming plant- and animal-based protein-rich foods on cardiovascular health of adults. Recent Findings Results from meta-analyses of RCTs exemplify the importance of considering relative effects of protein-rich foods, i.e., when intake of one food increases, intake of another food likely decreases. Results from short-term RCTs showed that overall diet quality is more influential for improving cardiovascular disease (CVD) risk factors than intake of a single protein-rich food, e.g., red meat. Yet, assessing long-term CVD risk associated with intake of a single protein-rich food as part of a dietary pattern is methodologically challenging. While accumulating evidence suggests gut microbiota as a potential mediator for such effects, current knowledge is preliminary and restricts causal or functional inferences. Summary A variety of protein-rich foods, both plant- and animal-based, should be consumed as part of nutrient-dense dietary patterns to meet nutrient needs and improve cardiovascular health for adults.
... Nuts are high in fibre and protein-nutrients, which may promote satiety. Satiety may be further enhanced by the crunchy textural property of whole nuts as the mechanical effort required for mastication with long oral residence time results in the cephalic response and secretion of appetitive hormones [17][18][19][20][21][22][23]. ...
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Consuming nuts may have advantages over other snack foods for health and body-weight regulation. Suggested mechanisms include increased satiety and lower glycaemia. We used an acute randomised crossover trial to assess glycaemic and appetite responses to consuming two isocaloric snacks (providing 10% of participants' total energy requirements or 1030 kJ (equivalent to 42.5 g almonds), whichever provided greater energy): raw almonds and sweet biscuits among 100 participants with available data (25 males and 75 females) following 106 being randomised. Two hours after consuming a standardised breakfast, participants consumed the snack food. Finger-prick blood samples measuring blood glucose and subjective appetite ratings using visual analogue scales were taken at baseline and at 15 or 30 min intervals after consumption. Two hours after snack consumption, an ad libitum lunch was offered to participants and consumption was recorded. Participants also recorded food intake for the remainder of the day. The mean area under the blood glucose response curve was statistically and practically significantly lower for almonds than biscuits (mean (95% CI) difference: 53 mmol/L.min (45, 61), p < 0.001). Only the composite appetite score at 90 min was higher in the almond treatment compared to the biscuit treatment (45.7 mm vs. 42.4 mm, p = 0.035 without adjustment for multiple comparisons). There was no evidence of differences between the snacks for all other appetite ratings or for energy intake at the ad libitum lunch. However, mean energy intakes following snack consumption were significantly lower, both statistically and in practical terms, for the almond treatment compared to the biscuit (mean (95% CI) diff: 638 kJ (44, 1233), p = 0.035). Replacing popular snacks with almonds may have advantages in terms of glycaemia and energy balance.
... Alper and Mattes (2002) showed the impact of peanut consumption on energy balance. However, McKiernan et al., (2010) suggested that groundnut processing does not compromise the lipid-lowering effects and does not negatively impact body weight. ...
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The groundnut (Arachis hypogaea L.), also called a peanut, is an important food legume and oilseed crop of the tropical and subtropical worlds. They are presently grown on about 29 million hectares of land in about 120 countries in different agro-climatic zones between latitudes 40ºS and 40ºN from where about 49 million tons of groundnut pods are harvested every year. It is native to South America and presently cultivated mainly in Asia (11.5 m ha), Africa (16.7 m ha) and the Americas (1.4 m ha) in their arid to semi-arid regions. On a large scale it is grown mainly in India, China, Nigeria, USA, Sudan, Myanmar, Argentina, Chad, Senegal and Tanzania. It is consumed world-wide due to its high-energy, protein and mineral contents. It is eaten raw, after roasting, frying, salting or boiling and is used in many preparations and confectionery products and its demand is increasing. Groundnut requires a warm growing season with well distributed rainfall of 500-1000 mm and is now cultivated across a wide range of climates, mostly rainfed with one or two types of protective irrigation. Though the world’s average productivity of groundnut is around 1650 kg ha-1, about 40% of countries had productivity of less than 1000 kg ha-1 due to poor soil fertility and erratic rainfall, and only 29% of the countries show their productivity >2000 kg ha-1. India and China which account for about 33% of the area, produce more than 51% of the groundnut and are major consumers as well as suppliers. However, in most of the African countries groundnut is grown on marginal soil under low input, and need the immediate attention of researchers and policy makers. India, USA, Argentina and the Shadong province of China have been producing the best quality groundnut in the world and had export demand the world over. On average the groundnut seed contains 45% oil, 25% protein, 6% sugar, 9% fiber, 6% moisture and 2% minerals besides several vitamins and phytochemicals. The consumption of groundnut is decided mainly based on its oil, protein and sugar contents and broadly categorized as oil types and confectionary types. The vitamins and minerals present in the seed increased its importance as medicinal and nutraceutical. The characteristics for confectionary uses are High sound mature seeds (SMS), no aflatoxin contamination, attractive seed size and shape, pink or tan seed color, flavour, low oil (<45%), low (<1%) free fatty acid (FFA), high sugars (> 6%), high protein (>24%) blanchability (>60%) and high Zn (> 50 mg kg-1).
... The New Zealand study also found that nut avoiders were more likely to avoid eating nuts because of dental issues, compared with nut butter avoiders. With evidence suggesting that there are no significant differences in health benefits between consuming different forms of nuts, including nut butters [69,70], it is reasonable that alternative forms of nuts that may pose fewer challenges for those with poor dentition could be recommended to this group of consumers. ...
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Habitual nut intake is associated with a range of health benefits; however, population consumption data suggests that most individuals do not meet current recommendations for nut intake. The literature has highlighted a range of barriers and facilitators to nut consumption, which should be considered when designing strategies to promote nut intake. Common barriers include confusion regarding the effects of nut consumption on body weight, perceptions that nuts are high in fat, or too expensive, and challenges due to dentition issues or nut allergies. Conversely, demographic characteristics such as higher education and income level, and a healthier lifestyle overall, are associated with higher nut intakes. Health professionals appear to play an important role in promoting nut intake; however, research suggests that knowledge of the benefits of nut consumption could be improved in many health professions. Future strategies to increase nut intake to meet public health recommendations must clarify misconceptions of the specific benefits of nut consumption, specifically targeting sectors of the population known to have lower nut consumption, and educate health professionals to promote nut intake. In addition, given the relatively small body of evidence exploring barriers and facilitators to nut consumption, further research exploring these factors is justified.
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Background Peanut consumption has little effect on body weight, despite its high energy density and is associated with reduced cardiovascular disease risk. Based on previous research, we hypothesized that the consumption of whole peanut would be associated with greater improvements in body composition, lipid profile, and biomarkers of inflammation and oxidative stress. Methodology Twenty-four women with obesity (BMI > 30 kg/m²), 33.1 ± 8.7 years old, were assigned to 3 groups and consumed 56 g of whole peanut (WP), skinned peanut (SP), and no peanut (NP) and consumed energy-restricted diets (250 kcal/d less than their customary diet) for eight weeks. Results WP lost an average of 3.2 kg, while SP group lost 2.6 kg and the NP group 1.8 kg. However, only the groups that consumed peanuts showed a significant reduction in body mass index (BMI). WP group presented lower body weight, BMI, waist circumference, total lean mass, and total body fat than the SP group in the 8th week. There was a significant reduction in total cholesterol and LDL after four weeks of intervention, which was maintained in week-8 for the WP and SP groups. In addition, there was an improvement in platelets and plasma homocysteine with WP. Conclusion Our results suggest that the regular intake of the whole peanut as part of an energy-restricted diet showed health benefits since it enhanced body weight loss, besides improving body composition and reducing cholesterol, platelets, and homocysteine concentrations. This article is protected by copyright. All rights reserved.
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Scope Peanuts are widely consumed as a meal ingredient and a snack, and are commonly considered as a healthy food based on their nutrient profile. Peanut consumption has been associated with a lower risk of metabolic syndrome (MetS) in epidemiological studies. In this study, we aimed to investigate whether consuming peanuts affects the gut microbiota in adults with risk of metabolic syndrome and whether the intervention effect of peanuts is associated with gut microbiota composition. Methods and results We analyzed the gut microbiota of subjects from a 12-week randomized clinical trial comparing consumption of either peanuts or isocaloric carbohydrate bars. We observed that there was high inter-individual variability on multiple clinical and anthropometrical parameters in response to peanut consumption. Meanwhile, the gut microbiota composition was also highly person-specific and had minor changes when compared laterally or longitudinally. We employed a machine-learning algorithm and established prediction models using the microbiome data and the responsiveness data of different parameters in subjects with peanut intervention. As a result, we found that the improvement of MetS risk and numerous parameters including diastolic blood pressure, body weight, waist circumference, and fasting blood glucose level could be predicted for responsiveness with high accuracy that had a value of area under curve over 0.70 by receiver operating characteristic analysis. Conclusion Together, our findings suggest that individual gut microbiota configuration may modulate host metabolism and alter an individual's response to peanut intervention, thus highlighting the importance of personalized nutrition. This article is protected by copyright. All rights reserved
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An abnormal ratio of triglycerides to HDL-cholesterol (TG/HDL-c) indicates an atherogenic lipid profile and a risk for the development of coronary disease. To investigate the association between lipid levels, specifically TG/HDL-c, and the extent of coronary disease. High-risk patients (n=374) submitted for coronary angiography had their lipid variables measured and coronary disease extent scored by the Friesinger index. The subjects consisted of 220 males and 154 females, age 57.2+/-11.1 years, with total cholesterol of 210+/-50.3 mg/dL, triglycerides of 173.8+/-169.8 mg/dL, HDL-cholesterol (HDL-c) of 40.1+/-12.8 mg/dL, LDL-cholesterol (LDL-c) of 137.3+/-46.2 mg/dL, TG/HDL-c of 5.1+/-5.3, and a Friesinger index of 6.6+/-4.7. The relationship between the extent of coronary disease (dichotomized by a Friesenger index of 5 and lipid levels (normal vs. abnormal) was statistically significant for the following: triglycerides, odds ratio of 2.02 (1.31-3.1; p=0.0018); HDL-c, odds ratio of 2.21 (1.42-3.43; p=0.0005); and TG/HDL-c, odds ratio of 2.01(1.30-3.09; p=0.0018). However, the relationship was not significant between extent of coronary disease and total cholesterol [1.25 (0.82-1.91; p=0.33)] or LDL-c [1.47 (0.96-2.25; p=0.0842)]. The chi-square for linear trends for Friesinger >4 and lipid quartiles was statistically significant for triglycerides (p=0.0017), HDL-c (p=0.0001), and TG/HDL-c (p=0.0018), but not for total cholesterol (p=0.393) or LDL-c (p=0.0568). The multivariate analysis by logistic regression OR gave 1.3+/-0.79 (p= .0001) for TG/HDL-c, 0.779+/-0.074 (p= .0001) for HDL-c, and 1.234+/-0.097 (p=0.03) for LDL. Analysis of receiver operating characteristic curves showed that only TG/HDL-c and HDL-c were useful for detecting extensive coronary disease, with the former more strongly associated with disease. Although some lipid variables were associated with the extent of coronary disease, the ratio of triglycerides to HDL-cholesterol showed the strongest association with extent.
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Epidemiologic and clinical trial evidence has demonstrated consistent benefits of nut and peanut consumption on coronary heart disease (CHD) risk and associated risk factors. The epidemiologic studies have reported various endpoints, including fatal CHD, total CHD death, total CHD, and nonfatal myocardial infarct. A pooled analysis of 4 U.S. epidemiologic studies showed that subjects in the highest intake group for nut consumption had an approximately 35% reduced risk of CHD incidence. The reduction in total CHD death was due primarily to a decrease in sudden cardiac death. Clinical studies have evaluated the effects of many different nuts and peanuts on lipids, lipoproteins, and various CHD risk factors, including oxidation, inflammation, and vascular reactivity. Evidence from these studies consistently shows a beneficial effect on these CHD risk factors. The LDL cholesterol-lowering response of nut and peanut studies is greater than expected on the basis of blood cholesterol-lowering equations that are derived from changes in the fatty acid profile of the diet. Thus, in addition to a favorable fatty acid profile, nuts and peanuts contain other bioactive compounds that explain their multiple cardiovascular benefits. Other macronutrients include plant protein and fiber; micronutrients including potassium, calcium, magnesium, and tocopherols; and phytochemicals such as phytosterols, phenolic compounds, resveratrol, and arginine. Nuts and peanuts are food sources that are a composite of numerous cardioprotective nutrients and if routinely incorporated in a healthy diet, population risk of CHD would therefore be expected to decrease markedly.
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Nuts (ground and tree) are rich sources of multiple nutrients and their consumption is associated with health benefits, including reduced cardiovascular disease risk. This has prompted recommendations to increase their consumption. However, they are also high in fat (albeit largely unsaturated) and are energy dense. The associations between these properties, positive energy balance, and body weight raise questions about such recommendations. This issue is addressed through a review of the literature pertaining to the association between nut consumption and energy balance. Epidemiological studies document an inverse association between the frequency of nut consumption and BMI. Clinical trials reveal little or no weight change with inclusion of various types of nuts in the diet over 1-6 mo. Mechanistic studies indicate this is largely attributable to the high satiety property of nuts, leading to compensatory responses that account for 65-75% of the energy they provide. Limited data suggest chronic consumption is associated with elevated resting energy expenditure resulting in dissipation of another portion of the energy they provide. Additionally, due to poor bioaccessibility, there is limited efficiency of energy absorption from nuts. Collectively, these mechanisms offset much of the energy provided by nuts. The few trials contrasting weight loss through regimens that include or exclude nuts indicate improved compliance and greater weight loss when nuts are permitted. This consistent literature suggests nuts may be included in the diet, in moderation, to enhance palatability and nutrient quality without posing a threat for weight gain.
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Nuts (ground and tree) are rich sources of multiple nutrients and their consumption is associated with health benefits, including reduced cardiovascular disease risk. This has prompted recommendations to increase their consumption. However, they are also high in fat (albeit largely unsaturated) and are energy dense. The associations between these properties, positive energy balance, and body weight raise questions about such recommendations, This issue is addressed through a review of the literature pertaining to the association between nut consumption and energy balance, Epidemiological studies document an inverse association between the frequency of nut consumption and BMI. Clinical trials reveal little or no weight change with inclusion of various types of nuts in the diet over 1-6 mo. Mechanistic studies indicate this is largely attributable to the high satiety property of nuts, leading to compensatory responses that account for 65-75% of the energy they provide. Limited data suggest chronic consumption is associated with elevated resting energy expenditure resulting in dissipation of another portion of the energy they provide. Additionally, due to poor bioaccessibility, there is limited efficiency of energy absorption from nuts. Collectively, these mechanisms offset much of the energy provided by nuts. The few trials contrasting weight loss through regimens that include or exclude nuts indicate improved compliance and greater weight loss when nuts are permitted. This consistent literature suggests nuts may be included in the diet, in moderation, to enhance palatability and nutrient quality without posing a threat for weight gain.
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Objective. —To determine the risk of elevated total homocysteine (tHcy) levels for arteriosclerotic vascular disease, estimate the reduction of tHcy by folic acid, and calculate the potential reduction of coronary artery disease (CAD) mortality by increasing folic acid intake.Data Sources. —MEDLINE search for meta-analysis of 27 studies relating homocysteine to arteriosclerotic vascular disease and 11 studies of folic acid effects on tHcy levels.Study Selection and Data Extraction. —Studies dealing with CAD, cerebrovascular disease, and peripheral arterial vascular disease were selected. Three prospective and six population-based case-control studies were considered of high quality. Five cross-sectional and 13 other case-control studies were also included. Causality of tHcy's role in the pathogenesis of vascular disease was inferred because of consistency across studies by different investigators using different methods in different populations.Data Synthesis. —Elevations in tHcy were considered an independent graded risk factor for arteriosclerotic vascular diseases. The odds ratio (OR) for CAD of a 5-μmol/L tHcy increment is 1.6(95% confidence interval [Cl], 1.4 to 1.7) for men and 1.8 (95% Cl, 1.3 to 1.9) for women. A total of 10% of the population's CAD risk appears attributable to tHcy. The OR for cerebrovascular disease (5-μmol/L tHcy increment) is 1.5 (95% Cl, 1.3 to 1.9). Peripheral arterial disease also showed a strong association. Increased folic acid intake (approximately 200 μg/d) reduces tHcy levels by approximately 4 μmol/L. Assuming that lower tHcy levels decrease CAD mortality, we calculated the effect of (1) increased dietary folate, (2) supplementation by tablets, and (3) grain fortification. Under different assumptions, 13 500 to 50 000 CAD deaths annually could be avoided; fortification of food had the largest impact.Conclusions. —A 5-μmol/L tHcy increment elevates CAD risk by as much as cholesterol increases of 0.5 mmol/L (20 mg/dL). Higher folic acid intake by reducing tHcy levels promises to prevent arteriosclerotic vascular disease. Clinical trials are urgently needed. Concerns about masking cobalamin deficiency by folic acid could be lessened by adding 1 mg of cobalamin to folic acid supplements.(JAMA. 1995;274:1049-1057)
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Oxidative modification of low density lipoprotein (LDL) plays an important role in the process of atherosclerosis. The susceptibility of LDL to oxidation and the amount of peroxidation products formed are influenced by the lipoprotein content of 18:1n-9, 18:2n-6, and the 18:2n-6/18:1n-9 ratio, which is dependent in part on dietary fatty acids. The purpose of this study was to determine if changing from a typical American diet to a low-fat, monounsaturate-rich diet (LFMR) would result in favorable alterations in the fatty acid composition and oxidative profile of LDL in hypercholesterolemic individuals. Free-living postmenopausal hypercholesterolemic women who routinely consumed a diet moderately high in total fat and total saturates (34 and 11%, respectively) followed an LFMR diet (26% fat, 6% saturated fat, and 14% monounsaturated fat) for 6 mon. Sixteen postmenopausal hypercholesterolemic women already following standard low-fat (LF) diets acted as a control for seasonal variations in serum lipids. LDL from randomly selected subjects (LF n = 6, LFMR n = 5) was evaluated. LFMR diets resulted in LDL with increased concentrations and percentages of 18:1n-9, reduced 18:2n-6/18:1n-9 ratio, and lower percentages of 18:2n-6. No significant changes in LDL fatty acids occurred in the LF group. Conjugated diene lag time increased in both groups during copper-induced in vitro oxidation. Only the LFMR group experienced an increase in lipid peroxide lag time and a decrease in lipid peroxide formation. The LFMR diet was well tolerated and may be of therapeutic value in the treatment of hypercholesterolemia.