The Journal of Nutrition
Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions
Pistachios Increase Serum Antioxidants
and Lower Serum Oxidized-LDL in
Colin D. Kay,3,4,6Sarah K. Gebauer,3,5,7Sheila G. West,3,4and Penny M. Kris-Etherton,3,5*
3Department of Nutritional Sciences,4Department of Biobehavioral Health, and5Integrative Biosciences, The Pennsylvania State
University, University Park, PA 16802
Pistachios are high in lutein, b-carotene, and g-tocopherol relative to other nuts; however, studies of the effects of
pistachios on oxidative status are lacking. We conducted a randomized, crossover controlled-feeding study to evaluate 2
doses of pistachios on serum antioxidants and biomarkers of oxidative status in 28 hypercholesterolemic adults (LDL-
cholesterol $2.86 mmol/L). Participants consumed 3 isoenergetic diets for 4 wk each after a 2-wk baseline Western diet.
Experimental diets included a lower-fat control diet without pistachios (25% total fat) with 1 serving/d (i.e. 32–63 g/d;
energy adjusted) of pistachios (1 PD; 10% energy from pistachios; 30% total fat) or with 2 servings/d (63–126g/d; energy
adjusted) of pistachios (2 PD; 20% energy from pistachios; 34% total fat). When participants consumed the pistachio-
enricheddiets,theyhad higherplasmalutein(P ,0.0001),a-carotene,andb-carotene(P ,0.01) concentrationsthanafter
the baseline diet. After consuming the pistachio diets, participants had greater plasma lutein (P , 0.001) and g-tocopherol
(P , 0.05; 2 PD only) relative to the lower-fat control diet. After the 2 PD diet period, participants also had lower serum
oxidized-LDL concentrations than following the baseline diet period (P , 0.05). After both the 1 PD and 2 PD diet periods,
they had lower serum oxidized-LDL concentrations than after the control diet period (P , 0.05). The change in oxidized-
LDL from baseline correlated positively with the change in LDL-cholesterol across all treatments (r = 0.42; P , 0.005).
After controlling for the change in serum LDL-cholesterol as a covariate, increases in serum lutein and g-tocopherol
following the 2 PD period were still modestly associated with decreases in oxidized-LDL (r = 20.36, P = 0.06 and r =
20.35, P = 0.08, respectively). This suggests that a heart-healthy diet including pistachios contributes to the decrease in
the serum oxidized-LDL concentration through cholesterol-lowering and may provide an added benefit as a result of the
antioxidants the pistachios contain. J. Nutr. 140: 1093–1098, 2010.
Epidemiologic and clinical studies have demonstrated consis-
tently significant cardiovascular benefits of tree nuts and peanuts
(1,2). The cardioprotective effects of tree nuts and peanuts have
been associated with their favorable fatty acid profiles in
addition to their bioactive constituents/phytochemicals (1,2).
We have shown previously that the inclusion of pistachios in a
healthy diet beneficially affects lipids and lipoproteins in a dose-
dependent manner (3). Relative to other nuts, pistachios are a
rich source of antioxidants, including lutein, b-carotene, and
g-tocopherol in addition to containing selenium, flavonoids, and
proanthocyanidins (4,5). As would be expected, pistachios have
a relatively high in vitro antioxidant capacity (6–8).
Oxidized LDL-cholesterol (9,10) and lipid peroxidation
products are found in elevated concentrations in atherosclerotic
plaques (11,12) and are thought to play an important role in the
development and progression of atherosclerosis (9–11,13).
Thus, strategies that reduce in vivo oxidative stress are thought
to confer cardioprotective effects. The present study was
designed to evaluate a dose-response effect of pistachios on
serum antioxidant status and oxidative biomarkers of cardio-
vascular disease (CVD)8.
Previous dietary interventions with pistachios conducted in
humans have shown improvements in lipoprotein profiles
1Supported by the Western Pistachio Association; postdoctoral fellowship (C.D.
K.) support by the Natural Sciences and Engineering Research Council of
Canada, and partial support from the General Clinical Research Center, The
Pennsylvania State University (NIH grant M01RR10732).
2Author disclosures: C. D. Kay, S. K. Gebauer, S. G. West, and P. M.
Kris-Etherton, no conflicts of interest.
6Present address: School of Medicine, University of East Anglia, Norwich, UK.
7Present address: Beltsville Human Nutrition Research Center, Agricultural
Research Service, USDA, Beltsville, MD.
* To whom correspondence should be addressed. E-mail: firstname.lastname@example.org.
8Abbreviations used: baseline diet, typical Western diet; control diet, lower-fat
diet with no pistachios; CVD, cardiovascular disease; GSH, glutathione; 1 PD,
diet of 1 serving of pistachios/d (;10% energy/d or 32-63 g/d; 2 PD, diet of 2
servings of pistachios/d (;20% energy of pistachios/d, or 63-126 g/d); TC, total
cholesterol; TG, triacylglycerol.
ã 2010 American Society for Nutrition.
Manuscript received October 13, 2009. Initial review completed November 11, 2009. Revision accepted March 16, 2010.
First published online March 31, 2010; doi:10.3945/jn.109.117366.
(7,14,15) and one reported a beneficial effect on serum antiox-
idant status (measured using a malondialdehyde assay) in 44
males and females who consumed a diet that provided 20% of
their energy as pistachios for 3 wk (7). However, all of these
studies were conducted in free-living individuals and none
controlled for SFA or antioxidant content of the background
diets. Therefore, it is difficult to establish the extent to which
pistachio-derived antioxidants contributed to the observed
effects on antioxidant capacity over the displacement of satu-
rated fat resulting from nut consumption. The present clinical
study of the antioxidant effects of pistachios is unique, because it
utilized a controlled-feeding crossover design and 2 doses of
pistachios and controlled for saturated fatintake. The aim of our
study was to evaluate the effects of supplementing a lower-fat
diet with pistachios [10% of energy/d from pistachios (1 PD)
and 20% of energy/d from pistachios (2 PD)] on serum oxidative
risk factors in a controlled-feeding trial. We evaluated serum
oxidative risk factors associated with CVD, including oxidized-
LDL and total lipid hydroperoxides, in addition to other
markers of serum global redox state, including serum tocoph-
erol, carotenoid, and uric acid and whole blood glutathione
concentrations. We hypothesized that a lower-fat diet sup-
plemented with 2 different doses of pistachios would dose-
dependently confer greater cardioprotective effects on antioxidant
status than the lower-fat control diet.
Participants and study design. Healthy, nonsmoking males and
females [n = 10 M, 18 F; ages 35–61 y, BMI = 26.8 6 0.7 kg/m2] with
moderately elevated LDL-cholesterol [.2.8 mmol/L; 50–95th percentile
based on NHANES data and the 3rd Adult Treatment Panel guidelines
(16)] completed the study. One participant dropped out of the study due
to an inability to comply with study protocol. Participants were required
to have triacylglycerol (TG) concentrations , 3.94 mmol/L, blood
pressure , 160/90 mm Hg, BMI between 21 and 35 kg/m2, and fasting
blood glucose # 6.9 mmol/L. The followingexclusion criteria were used:
use of blood pressure or cholesterol-lowering medication; supplemental
use of psyllium, fish oil, soy lecithin, or phytoestrogens; being pregnant
or wishingto become pregnant6 mo before or duringthe study; lactating
6 wk before or during the study; having weight loss $ 10% body weight
6 mo prior to the study; following vegetarian or weight-loss diets; having
diabetes, liver, kidney, or autoimmune diseases, or previous stroke; and
inability to comply with the study protocol. A complete list of baseline
characteristics (including blood pressure, glucose, insulin, and other
parameters) has been reported previously (3). The study was approved
by the Institutional Review Board at The Pennsylvania State University
and all participants gave written informed consent prior to enrollment.
A 3-period randomized, crossover controlled-feeding design was
implemented. All participants consumed a 2-wk run-in diet, which was a
typical Western diet that served as their baseline diet. They were then
randomized to each of the 3 experimental diets for 4 wk. Short
compliance breaks (average of 2 wk) separated the diet periods.
Diets. Theenergyand macro-andmicronutrientcompositions ofthetest
diets (Table 1) were determined by Nutritionist Pro (Axxya Systems)
approximations and approximated from the USDA Nutrient Database
(5) where necessary. All test diets were isoenergetic and matched for
saturated fat [;8% of energy] and cholesterol (,300 mg/d); they varied
in the amount of unsaturated fat provided by the pistachios. The diets
varied intotalfatwithintherangeof 25–35%ofenergyasrecommended
by the 3rd Adult Treatment Panel of the National Cholesterol Education
Program (16). Diets also were matched for the antioxidants vitamins A,
C, and E, tocopherols, lutein, selenium, and folate. The baseline diet and
control diet did not containpistachios. Pistachiointakewas calculatedas
10 and 20% of energy for the 1 PD and 2 PD, respectively. Pistachio
amounts ranged from 32 to 63 g/d for the 1 PD and 63 to 126 g/d for the
2 PD, depending on energy level. All food was prepared and consumed
by the participants at the Metabolic Diet Study Center at The
Pennsylvania State University. They ate 1 meal per day in the center
and had their other meals and snacks packed for offsite consumption.
Adherence to the experimental diets was checked daily using compliance
questionnaires. In addition, participants were weighed daily to assess
compliance and ensure that body weight was maintained. Specific details
of the diet protocol have been described elsewhere (3).
Data collection. Blood samples were collected in the morning after a
12-h fast on 2 consecutive days at the end of each diet period by nurses
at The Pennsylvania State University General Clinical Research Center
(University Park, PA). Serum oxidation markers (oxidized-LDL, lipid
hydroperoxides), antioxidant status measures (tocopherols, carotenoids,
uric acid, and glutathione), and serum lipid and lipoprotein concentra-
tions were measured at the end of each feeding period. Serum for
oxidation and antioxidant analysis was collected on 1 d, whereas plasma
for lipid and lipoprotein analysis was collected on 2 consecutive days
(and averaged for consistency). Blood was collected into Vacutainer
tubes(VWRScientificProducts),allowedtoclot atroom temperature for
g at 08C. Serum was immediately aliquoted into cryovials (VWR Sci-
entific Products), flash-frozen in liquid nitrogen, and stored at 2808C
until the completion of the study. Blood samples used for measuring
glutathione were first treated with 1-methyl-2-vinylpyridinium trifluor-
omethanesulfonate and samples for tocopherol and carotenoid analysis
were collected in amber cryovials.
Analytical methods. Serum oxidized LDL were measured by a solid
phase 2-site ELISA (Mercodia Oxidized LDL ELISA, no. 10–1158–01;
Alpco Diagnostics) based on the direct sandwich technique and adapted
from previous studies (17) (intraassay CV = 3.2%). The lipid hydroper-
oxide assay measures hydroperoxides in the isolated lipid-phase of the
serum directly following ferrous ion reduction. This assay involves the
Cayman LPO kit (no. 705003) that is based on the FOX assay but has
been modified for use with a 96-well plate reader (intraassay CV =
3.6%). Whole blood glutathione was measured enzymatically utilizing a
commercially available assay (GSH/GSSG412Colorimetric Determina-
tion assay no. 21040; Oxis International) that was modified for use with
a 96-well plate reader (intraassay CV = 1.4%).
Daily energy, macronutrient, and micronutrient
intakes during the 4 diet periods1
Control 1 PD2 PD
Vitamin C, mg
Vitamin E, mg
Lutein and zeaxanthin, mg
1Values are Nutritionist Pro approximations; complete nutrient compositions (includ-
ing fatty acids, sodium, potassium, etc.) described in greater detail elsewhere (3).
Percent kJ values are presented in parentheses.
2MUFA, Monounsaturated fatty acids.
3Values were approximated from the USDA Nutrient Database (5).
1094Kay et al.
Serum tocopherol (a and g) and carotenoid (a and b) analyses were
conducted in the laboratory of Dr. Thomas Wilson at the Department of
Clinical Laboratory and Nutritional Sciences, University of Massachu-
setts (Lowell, MA) using HPLC with photodiode array detection for
carotenoids and fluorescence detection for tocopherols. Samples were
prepared according to the procedures described by Handelman et al.
(18). Uric acid was measured commercially by ZeptoMetrix using a
Cobas Mira (Roche, no. 25–4668) clinical automated chemical analyzer
and standard methods (19,20).
Total cholesterol (TC) and TG were determined by enzymatic
procedures with commercially available kits (TC, CHOP/PAP, Boer-
inger; TG and free glycerol, Abbott Laboratories, Diagnostic Division).
HDL-cholesterol was estimated according to the modified heparin-
manganese precipitation procedure of Warnick and Albers (21), whereas
LDL-cholesterol was calculated byFriedewald’s equation.Intraassay CV
ranged from 1.5 to 1.6% for lipids and lipoproteins.
Statistical analyses.All statistical analyses were performed using SAS
(version 9.1). Normality was assessed via the Shapiro-Wilk test
utilizing the residuals for each variable. Logarithmic or other appro-
priate transformations were used for variables that did not have
normal distributions [lipid hydroperoxides and glutathione (GSH)].
ANOVAwas used to determine whether the outcome variables differed
among the 4 dietary conditions (baseline, control, 1 PD, 2 PD).
Specifically, the mixed models procedure (PROC MIXED) was used to
test whether the main effects of treatment, period, and order, or their
interactions, were significant. Models included treatment, period,
order, and their interactions as fixed effects and participant as a
random effect. If an effect was significant (P # 0.05; as for oxidized-
LDL, a-tocopherol, g-tocopherol, b-carotene, lutein, lycopene), we
examined the effect of treatment on the magnitude of change
(calculated as treatment 2 baseline) using the mixed model procedure.
In this case, treatment was the fixed effect and participant was the
random effect. Degrees of freedom were adjusted for unequal group
variance by Satterthwaite’s approximation. Tukey-Kramer adjusted
P-values were used to examine the source of significant effects for all
mixed models. Values are presented as least squares mean 6 SEM.
P-values were considered significant at P # 0.05. A post hoc analysis of
lipid-adjusted carotenoids and tocopherols was conducted where
concentrations were divided by the total level of plasma cholesterol
and statistically analyzed using the above protocol. For variables that
significantly changed with treatment, correlation analysis was used to
examine whether individuals exhibiting greater increases in serum
concentrations of pistachio-derived antioxidants also had greater
changes in biomarkers of oxidation.
Compliance to the study protocol was very good, as indicated
bydaily compliance questionnaires andmaintenance of prestudy
uric acid, lutein, lycopene, zeaxanthin, a-carotene, b-carotene,
g-tocopherol, and a-tocopherol concentrations (Table 2). How-
ever, concentrations of total lipid peroxides, glutathione, and
zeaxanthin did not change from baseline. The magnitude of
changes in uric acid from baseline after the pistachio and control
diet periods did not differ (data not shown). Diet order did not
affect any of these variables.
Serum antioxidants. Serum lutein was greater following
consumption of the 1 PD and 2 PD diets compared with the
baseline andcontrol diets and wasgreater after the 2 PDthan the
1 PD period, indicating a dose-effect (P , 0.0001) (Table 2; Fig.
1). In addition, the change in serum lutein from baseline was
inversely correlated with the change in serum lycopene after
consumption of the 2 PD diet (r = 20.5; P # 0.01).
Serum a-carotene (P , 0.01) and b-carotene (P , 0.01)
increased from baseline following the 1 PD and 2 PD periods
(Table 2). However, compared with the control diet, the percent
increase in serum b-carotene from baseline was significant only
following the 2 PD period (P , 0.05) (Fig. 1A). After the 2 PD
diet period, participants had a greater serum g-tocopherol
concentration (Table 2) and percent increase (Fig. 1A) compared
with the control diet period. The percent decrease from baseline
in the serum a-tocopherol concentration after the 2 PD period
also was significantly greater than after the control diet or the
1 PD period (Fig. 1A).
Serum lycopene was higher in the participants following
consumption of the baseline diet (P , 0.01) relative to all of the
dietary treatments and was higher following the control diet
post hoc analysis of lipid-adjusted carotenoids (ratio of carote-
not differ between the control diet and 2 PD periods (Fig. 1B).
Oxidative biomarkers. After the 2 PD period, participants had
lower oxidized-LDL concentrations relative to baseline (P ,
Circulating concentrations of biomarkers of oxidative stress, antioxidants, and
LDL-cholesterol in healthy, moderately hypercholesterolemic men and women before and
after consuming 0, 1, and 2 servings of pistachios/d for 4 wk1
BaselineControl1 PD 2 PD
Lipid hydroperoxide, mmol/L
Uric acid, mmol/L
a-Tocopherol , nmol/L
48.57 6 3.02
0.60 6 0.21
269.04 6 17.70
934.71 6 27.33
10.06 6 0.79
31.35 6 1.51
230.72 6 21.89
674.37 6 33.62
51.22 6 3.41
232.18 6 31.66
561.22 6 52.75
3.43 6 0.11
51.29 6 3.02a
0.50 6 0.21
245.44 6 17.70*
916.44 6 27.15
9.72 6 0.79a
31.23 6 1.51a
239.37 6 21.89a
616.69 6 33.62a*
63.84 6 3.41a*
304.52 6 31.66a
642.84 6 52.75a
3.42 6 0.11a
46.57 6 3.03b
0.54 6 0.21
248.98 6 17.70a *
874.26 6 27.82
10.68 6 0.79a
30.97 6 1.51a
337.77 6 22.03b*
571.74 6 33.94a*
61.23 6 3.43a*
345.41 6 32.02a*
706.52 6 54.97a*
3.08 6 0.11b*
43.43 6 3.02b*
0.65 6 0.21
244.85 6 17.70*
847.02 6 27.33
11.28 6 0.79b
28.44 6 1.51a
421.89 6 21.89c*
506.25 6 33.62b*
61.81 6 3.40a*
337.53 6 31.66a*
714.87 6 52.75a*
2.98 6 0.11b*
1Values are expressed as mean 6 SE, n = 28. *Significantly different from baseline, P , 0.05. Means for diet treatments with superscripts
without a common letter differ, P # 0.05.
2Effect of treatment (raw values).
Pistachios decrease LDL oxidation 1095
0.05) whereas both the 1 PD and 2 PD periods resulted in lower
post-treatment concentrations compared with the control diet
(P ,0.05)(Table 2).Inaddition,thepercentdecreaseinoxidized-
LDL from baseline after the 2 PD period was greater than
following the control diet (P , 0.0001) (Fig. 1A). Correlation
analysis revealed that increases in lutein and g-tocopherol
following the 2 PD period were correlated with the decreases in
oxidized-LDL (r = 20.37 and r = 20.38, respectively; P = 0.05).
There was a dose-dependent decrease in the atherogenic
lipoprotein profile (LDL-cholesterol:HDL-cholesterol ratio) af-
ter the pistachio diet periods, as reported elsewhere (3). The
change in LDL-cholesterol from baseline was positively corre-
lated with the change in oxidized-LDL across all treatments,
indicating that the absolute concentration of LDL was the
greatest determinant of oxidized LDL concentrations (r = 0.42;
P = 0.002). Additional post hoc correlation analyses were
and oxidized-LDL by using the change in LDL-cholesterol as a
covariate; this slightly reduced the significance of the association
between the changes in serum lutein (r = 20.36; P = 0.06) and
g-tocopherol (r = 20.35; P = 0.08) with the change in oxidized-
The present study demonstrates beneficial effects of pistachios
on multiple biomarkers of oxidative state. We found significant
decreases in serum oxidized-LDL in participants following the
pistachio-enriched treatment diets relative to the control diet.
This is important, because oxidized-LDL are recognized as a
contributing factor for the initiation and progression of CVD
(9,10). The decrease in oxidized-LDL was accompanied by a
significant increase in serum concentrations of antioxidants
(relative to the control diet), including g-tocopherol (2 PD),
lutein (1 PD and 2 PD), and b-carotene (2 PD) (Fig. 1A), thus
indicating a beneficial effect of pistachios on concentrations of
serum antioxidants. Furthermore, changes in serum lutein and
g-tocopherol were correlated with changes in oxidized-LDL
during the 2 PD period, suggesting that pistachio’s antioxidants
confer cardiovascular benefits that are associated with their
favorable effects on oxidized-LDL.
Significant increases in g-tocopherol were associated with
decreases in a-tocopherol following the pistachio interventions,
resulting in significantly lower a-tocopherol concentrations in
participants following the 2 PD diet compared with the control
diet period. This is a known effect of tocopherol supplementa-
tion, as one tocopherol species can inversely affect the levels of
the other, although this response is generally observed at much
higher intakes (22,23).
Serum lycopene was significantly lower following both the
pistachio diet periods relative to the control diet period. The
diets were initially matched for vitamins A, C, and E, tocoph-
erols, and lutein, but were not initially matched for lycopene
specifically. Therefore, slight differences in the amount of
tomato products between the treatments could have resulted in
the diets having different quantities of lycopene (24–26). In fact,
postintervention HPLC analysis of representative diet treat-
ments indicated that the lycopene concentration of the control
diet (1.7 mg/g) was higher than the 1 PD (1.2 mg/g) and 2 PD (1.0
mg/g) diets, thus explaining the lower serum concentrations of
lycopene following the pistachio treatments. However, when
serum carotenoids were expressed relative to TC (i.e. lipid-
adjusted ratios; Fig. 1B), the differences in lipid-adjusted ly-
copene concentrations between pistachio treatments and the
control diet period were no longer significant.
Despite the decreases in lycopene, a-tocopherol, and uric acid
following the diet treatments, participants still had significantly
lower circulating oxidized-LDL concentrations following con-
sumption of the pistachio diets. This suggests that foods that
have multiple antioxidants, like pistachios, may be critically
important in reducing a biomarker of chronic disease such as
In the present investigation, there were significant decreases
in uric acid in participants following consumption of the 1 PD
and 2 PD, compared with baseline (P , 0.05). However, the
magnitude of change in uric acid from baseline did not differ
after consumption of the pistachio and control diets. Therefore,
differences in uric acid do not appear to confound the observed
adjusted (B) serum biomarkers of oxidative stress, antioxidants, and
oxidized-LDL in healthy, moderately hypercholesterolemic men and
women before and after consuming 0, 1, and 2 servings of pistachios/d
for 4 wk. The absolute change (difference between baseline and
treatment; change score) was calculated only for variables significantly
altered from baseline and having significant treatment effects in the
mixed model analysis of raw data. The lipid-adjusted serum carote-
noids and tocopherols were established relative to TC, while oxidized-
LDL were adjusted to LDL-cholesterol concentrations. Values are
expressed as mean 6 SEM, n = 28. Means for diet treatments
without a common letter differ: *P # 0.05, **P # 0.01, ***P # 0.001,
****P # 0.0001. Abbreviations: Car, carotene; LDL-C, LDL-cholesterol;
Lycop, lycopene; OX-LDL, oxidized-LDL; Toc, tocopherol.
Percent change from baseline in absolute (A) and lipid-
1096Kay et al.
effects of the pistachio diets on oxidized-LDL. It is difficult to
identify the cause of the decrease in serum uric acid following
the pistachio diet periods; however, it may be the result of
differences in the amount of purines (27–29) in the baseline and
experimental dietsas a result ofdisplacing 10 and20%of energy
with pistachios. In the present investigation, all uric acid
concentrations were within the normal clinical range (29,30).
Previous studies have found that acute consumption of
walnuts or almonds (at 75% energy intake) improves postpran-
dial serum antioxidant status in humans, as measured by the
total radical absorption potential, ferric reducing antioxidant
potential, and oxygen radical absorption capacity assays (31). In
contrast, chronic (8 wk) consumption of walnuts or cashews
(20% energy intake) did not alter antioxidant status, as
measured using the oxygen radical absorption capacity and
prooxidant burden assays and serum GSH, in another study
(32). The inconsistency in findings from studies of nut con-
sumption has been described in several recent reviews (1,2,33).
Much of this inconsistency has been attributed to a general lack
of control for dietary saturated fat and/or antioxidant intakes
between the control and treatment diets within studies.
One dietary intervention with pistachios in humans has
shown beneficial effects on serum antioxidant status as mea-
sured bythe malondialdehydeassay (7). However,this study was
conducted in free-living individuals and, as suggested above,
dietary SFA and antioxidant intakes were not matched among
the groups, making it difficult to distinguish the contribution of
antioxidants within the nuts to any change in antioxidant
capacity compared with the effects of the displacement of
saturated fat on serum lipoproteins and oxidation. The novelty
of our study is that it was a controlled-feeding study designed
not only to control for SFA intake but also levels of antioxidants
in the background diets.
There was no effect of the pistachio treatments on serum lipid
hydroperoxides or glutathione in the present study. Because we
corrected for many of the shortfalls of previous nut interven-
tions, including controlling for dietary SFA and background diet
antioxidant content, we attribute the differential effects on the
various antioxidant activity measures (i.e. lipid hydroperoxides
and glutathione) to complexities in the measurement of redox
state in human studies. The lack of effect of the pistachio
treatments on these serum biomarkers of antioxidant status may
be the result of differential rates of oxidation of proteins (i.e.
lipoproteins) compared with lipids, differential activities of the
various serum antioxidants, a lower sensitivity of the assays
relative to the oxidized-LDL ELISA, or a basic lack of
responsiveness of basal redox state in relatively healthy individ-
uals. These are common limitations in studies investigating
antioxidant status/antioxidant activity (34,35).
In summary, oxidized-LDL were correlated with LDL-
cholesterol across all treatments (within- participant variation)
and serum lutein and g -tocopherol were associated with
reductions in oxidized-LDL following the 2 PD relative to the
control diet period. When controlling for changes in LDL-
cholesterol as a covariate in correlation analysis, the associations
between lutein, g-tocopherol, and oxidized-LDL lost some
statistical power but still suggested an added benefit of the 2
PD. In addition, the consumption of the pistachio diets resulted
in significant lowering of LDL-cholesterol as well as a dose-
dependent lowering of the atherogenic lipoprotein profile
(LDL-cholesterol:HDL-cholesterol ratio) (3). Overall, our study
suggests that consumption of pistachios in the context of a heart-
healthy diet confers cardioprotective benefits beyond established
lipid-lowering effects, including a decrease in oxidized-LDL,
which we think is the result of both a decrease in LDL-
cholesterol concentrations and an increase in serum antioxi-
dants, such as lutein and g-tocopherol.
In conclusion, the consumption of the pistachio-enriched
diets resulted in increases in serum antioxidants and decreases in
oxidized-LDL relative to the control diet. These data suggest
that a heart-healthy diet rich in pistachios has a beneficial effect
on serum antioxidants, as well as oxidized-LDL. Beneficial
effects on multiple CVD risk factors would be expected to
reduce overall CVD risk beyond that achieved by decreases in
We thank Dr. Thomas Wilson at the Department of Clinical
Laboratory and Nutritional Sciences, University of Massachu-
setts, for measuring serum tocopherol and carotenoids. C.D.K.,
S.K.G., S.G.W., and P.M.K-E. designed the research; C.D.K.
and S.K.G. conducted the research; C.D.K. and S.K.G. analyzed
the data; C.D.K., S.K.G., S.G.W., and P.M.K-E. wrote the
manuscript. C.D.K. had primary responsibility for final content.
All authors read and approved the final manuscript.
1.Ros E. Nuts and novel biomarkers of cardiovascular disease. Am J Clin
Serum concentrations of lipid-adjusted carotenoids and tocopherols in healthy, moderately
hypercholesterolemic men and women before and after consuming 0, 1, and 2 servings of
pistachios/d for 4 wk1,2
1 PD2 PD
0.020 6 0.001
0.064 6 0.002
0.63 6 0.07
1.71 6 0.08
0.14 6 0.01
0.59 6 0.08
1.42 6 0.1
0.019 6 0.001a
0.063 6 0.002
0.64 6 0.07a
1.57 6 0.08a
0.17 6 0.01a*
0.77 6 0.08a
1.63 6 0.1a
0.023 6 0.001b*
0.068 6 0.002
0.99 6 0.07b*
1.57 6 0.08a
0.18 6 0.01a*
0.94 6 0.08a*
1.93 6 0.1b*
0.024 6 0.001b*
0.064 6 0.002
1.26 6 0.07c*
1.42 6 0.08a*
0.18 6 0.01a*
0.95 6 0.08a*
2.00 6 0.1b*
1Values are expressed as mean 6 SE n = 28. *Significantly different from baseline, P , 0.05. Means for diet treatments with superscripts
without a common letter differ, P # 0.05.
2Lipid-adjusted serum carotenoids and tocopherols are expressed relative to TC.
3Effect of treatment (raw values).
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