Effect of Walnut-Enriched Restructured Meat in the
Antioxidant Status of Overweight/Obese Senior Subjects
with at Least One Extra CHD-Risk Factor
Amaia Canales, Juana Benedı ´, PhD, Meritxell Nus, PhD, Josana Librelotto, PhD, Jose M Sa ´nchez-Montero, PhD,
Francisco J. Sa ´nchez-Muniz, PhD
Departamento de Nutricio ´n y Bromatologı ´a I (Nutricio ´n) (A.C., M.N., J.L., F.J.S.-M.), Departamento de Farmacologı ´a (J.B.),
Grupo de Biotransformaciones (J.M.S.-M.), Departamento de Quı ´mica Orga ´nica y Farmaceu ´tica, Facultad de Farmacia (A.C.,
J.B. M.N., J.L., J.M.S.-M., F.J.S.-M.), Universidad Complutense, Madrid, SPAIN
Key words: antioxidant status, functional food, lipid peroxidation, walnut-enriched meat
Background: A number of recent studies indicate that antioxidants reduce the oxidative stress associated
with the development of coronary heart diseases (CHD).
Objective: (i) To investigate whether the erythrocyte catalase (CAT), superoxide dismutase (SOD), total
glutathione, reduced glutathione (GSH), oxidized glutathione (GSSG), and lipid peroxidation (LPO), and serum
uric acid and paraoxonase-1 (PON1) are modified at increased CHD-risk individuals consuming walnut-enriched
meat (WM), (ii) to evaluate whether these changes were influenced by basal serum cholesterol, body mass index
or smoking habit.
Design: The study was a non blinded, cross-over, placebo-controlled trial in which 22 volunteers (60%
overweight and 40% obese) with increased CHD-risk were randomly assigned to receive WM or control meat
(CM) during two different periods of 5 weeks.
Results: A significant interaction time*treatment (p ? 0.05) was observed in all enzymes and substrates
tested except HDL-C, uric acid and LPO. The treatment significantly increased CAT activity, total glutathione
and GSSG (p ? 0.05). Significant gender*time*treatment interaction (p ? 0.043) for total glutathione was found
increasing at the end of the WM period in male but not changing in female. Total glutathione and GSH/GSSG
ratio (p ? 0.05) were lower in smokers. Hypercholesterolemics presented higher uric acid (p ? 0.05) but no
enzyme activities or substrate concentrations were different from those of normocholesterolemics.
Conclusions: The WM tested appears to be a functional food as it improved the antioxidant status of
increased CHD-risk volunteers. Despite its high energy content, it also appears adequate for overweight and
obese people because did not exert negative effect upon body weight.
Prevention measures of coronary heart diseases (CHD) in-
clude modification of diet, which is one of the main factors
involved in the development of such diseases. Frequent intake
of walnuts correlates inversely with myocardial infarction or
mortality due to vascular ischemic disease, regardless of other
risk factors, such as age, overweight, hypertension, smoking
and lack of exercise [1–4]. Therefore, because of the potential
health benefits attributed to walnuts, an increase in their con-
sumption has been recommended [2,5].
The nutrient and phytochemical composition of walnuts
differs from that of other nuts. They are rich in ?-linoleic,
?-linolenic and ?-linolenic acids and in other health-related
compounds such as high-biological-value proteins (e.g. argi-
nine) fibre, vitamins, tannins, folates and polyphenols which
may provide additional antiatherogenic properties [6,7].
Address correspondence to: Professor Dr. Francisco J. Sa ´nchez-Muniz, Departamento de Nutricio ´n y Bromatologia I (Nutricio ´n), Facultad de Farmacia. Universidad
Complutense, E-28040-Madrid, SPAIN. E-mail: email@example.com
Abbreviations: BMI ? Body mass index, CHD ? Coronary heart disease, CAT ? Catalase, Hb ? Haemoglobin, CM ? Control meat, LPO ? Lipid peroxidation, MDA ?
Malondialdehyde, GSSG ? Oxidized glutathione, ox-LDL ? Oxidized-LDL, PON1 ? Paraoxonase, PUFA ? Polyunsaturated fatty acids, ROS ? Reactive oxygen
species, GSH ? Reduced glutathione, SOD ? Superoxide dismutase, WM ? Walnut-enriched meat.
Journal of the American College of Nutrition, Vol. 26, No. 3, 225–232 (2007)
Published by the American College of Nutrition
Spanish diet has deeply changed throughout last decades
with increased in total fat, saturated fatty acids (SFA) and a
reduction in vegetable and fatty fish consumptions . Thus,
walnuts intake could improve the quality of the Spanish diet. At
present, and despite all these facts, walnut consumption remains
low in Spain (2.65 g/day in 2004)  and other Mediterranean
countries . Consequently, several strategies, the most im-
portant of which has been the inclusion of walnuts in functional
foods, have been adopted to increase their intake .
A plethora of physiological disorders and degenerative dis-
eases have been related to oxidative stress [12,13]. Oxidative
stress may occur when production of reactive oxygen species
(ROS) increases and/or when scavenging free radicals or re-
pairing capacities against oxidative damage decreases or fails
. Measurement of malondialdehyde (MDA) and 4-hydroxy-
alkenals has been used as an indicator of lipid peroxidation
(LPO) . A variety of non-enzymatic antioxidants (e.g.
glutathione, uric acid) and enzymatic antioxidants (e.g. catalase
(CAT), Cu-Zn-superoxide dismutase (SOD)) have been known
to play an active role against oxidative stress [13,14]. During
recent years, the paraoxonase enzyme (PON-1) has become
relevant, due to its implications in the protection and recovery
of LDL antioxidant status . Free radicals and peroxides are
clearly involved in physiological phenomena but also in the
pathogenesis of several diseases such as atherosclerosis and
type-2 diabetes [12,13,17]. In fact, LDL peroxidation is ac-
cepted as the initial step of the atherosclerotic process .
Moreover, hypercholesterolemic or obese/overweight subjects
have higher levels of serum and LDL peroxidation than their
normocholesterolemic or slim counterparts .
Thus, it can be hypothesized that the intake of restructured
beef steaks and sausages containing walnuts may modify oxi-
dative stress in individuals with increased CHD risk. The
present study aims (i) to compare the effects of walnut-enriched
meat (WM) vs. control meat (CM) on oxidative stress by
measuring CAT, SOD and PON-1 activities, as well as the
concentrations of uric acid, GSH and GSSG; (ii) to ascertain if
these changes depend on the body mass index (BMI), basal
serum cholesterol concentrations or the smoking habit.
SUBJECTS AND METHODS
Candidates to participate in the study were recruited through
announcements. Volunteers had to fulfil the following eligibil-
ity criteria: a) high meat consumption (?5times/week); b) age:
men ?45 years; women (?50 years and postmenopausal) and
c) BMI ?25-?35 kg/m2. Volunteers having BMI ?30 kg/m2
were defined as obese. Moreover, at least one of the following
criteria was also required: serum total cholesterol ?5.69
mmol/L; smoking habit (?10 cigarettes per day); and/or hy-
pertension (systolic pressure ?140 mmHg and/or diastolic
pressure ?90 mm Hg). Exclusion criteria included subjects
with familiar hypercholesterolemia and/or type I diabetes;
those taking any hypolipemiant, antihypertensive or anti-in-
flammatory drugs and those receiving hormonal substitutive
therapy. The characteristics of volunteers are presented in Ta-
Procedures followed were in accordance with the ethical
standards of the Ethics Committee of the University Hospital of
Puerta de Hierro (Madrid, Spain) and the Helsinki Declaration,
as indicated in the guidelines of the Scientific Technologic
Project AGL 2001-2398-C03. Volunteers provided informed
consent previous to the start of the study.
Volunteers were randomly assigned to follow a non-
blinded, cross-over, placebo-controlled study, consisting of two
5-week experimental periods (intervention and control). Both
periods were separated by a 4 to 6-week wash-out interval
during which subjects returned to their usual diet. During the
intervention period, volunteers weekly consumed four 150g
walnut-enriched restructured steaks and a 150g ration of wal-
nut-enriched sausages, all containing 20% in walnut paste. The
composition of both meats is presented in Table 2 and more
information can be obtained in . It was firmly recom-
mended that all other meats and meat derivatives had to be
excluded from the diet. During the control period, volunteers
consumed identical amounts of restructured steaks and sau-
sages that did not include walnut paste.
The estimate of 10-year CHD-risk was evaluated according
to the ATP III indications .
Dietary Control and Compliance
Subjects received control and walnut-enriched frozen meat
once a week. Special emphasis was given to compliance and
management of intake with regard to frequency, dates and
numbers of steaks consumed. Energy and nutrient intakes were
Table 1. Basal Characteristics of Participants at Study Entry
Gender Males 60% (n ? 12)
Females 40% (n ? 10)
Body Mass Index (kg/m2)
54.8 ? 8.3
81.0 ? 12.9
29.6 ? 3.4 25–29.99 kg/m2, 60%
?30 kg/m2, 40 %
?10 cigarettes/day, 18%Smokers
Systolic Pressure (mmHg)
Diastolic Pressure (mmHg)
Total Cholesterol (mmol/L)
ATP III (10% year risk)
142.0 ? 22.0 ?140 mmHg, 64%
98.3 ? 25.8 ?90 mmHg, 72%
5.64 ? 1.12 ?5.69 mmol/L, 60%
12.3 ? 4.3
Data correspond to the mean ? SD of 22 volunteers.
Walnuts and Antioxidant Status
226VOL. 26, NO. 3
calculated using Food Composition Tables for the foodstuff
raw weights . In order to avoid any possible dietary mis-
understanding, volunteers recorded the amount and type of
food consumed on a daily basis. Compliance was also assessed
by measuring plasma ?-tocopherol concentrations after each
experimental period .
Anthropometric and Blood Pressure Measurements
Trained staff measured weight, height, BMI and systolic
and diastolic blood pressures of the participants at the begin-
ning and end of the intervention and control periods.
Fasting blood samples were collected between 7:30 and
10:00 a.m. at the beginning of the study and at the end of each
experimental period. Blood was gently delivered into citrate
tubes for SOD, CAT, GSH, and GSSG analysis and in vacu-
tainer tubes for PON-1, serum cholesterol and uric acid deter-
Preparation of Haemolysates
Citrated blood was centrifuged at 1000 ? g for 10 min at
4°C, and the plasma and buffy coat removed. Erythrocytes
were washed with PBS (pH 7.00, containing 140 mM NaCl)
three times and erythrocytes were haemolyzed with ice-cold
distilled water. Haemoglobin (Hb) content was determined by
using the cyanmethemoglobin method . Haemolysates
were used to determine SOD and CAT enzymatic activities and
GSH and GSSG concentrations.
Total and HDL-Cholesterol
Serum total and HDL-cholesterol were measured by enzy-
matic colorimetric method (CHOD-PAP, Boehringer Mann-
heim; RA-XT auto analyzer, Technicom; and RA 2000, Tech-
Uric acid was determined by the method of Trinder .
SOD (EC 1.15.11) was determined by the Marklund and
Marklund method , based on pyrogallol autoxidation. One
unit of enzyme activity was defined as 50% inhibition of the
rate of pyrogallol autoxidation. Results were expressed as IU/g
CAT (EC 184.108.40.206) activity was estimated by the Aebl
method , monitoring the rate of disappearance of hydrogen
peroxide at 240 nm. CAT activity is expressed as IU/g Hb.
Total Glutathione, GSH and GSSG Concentrations
Total glutathione (GSH plus GSSG) was measured by flu-
orometry, according to the Hissin and Hilf method , using
o-phthaldialdehyde. GSH and GSSG results were expressed as
PON1 (EC 220.127.116.11) activity was determined by measuring
the rate of hydrolysis of paraoxon in p-nitrophenol catalyzed by
the enzyme at 37°C and 405nm . Frozen aliquots of pool sera
were used as internal control. One unit of PON-1 activity was
defined as 1 ?mol of p-nitrophenol formed per L per minute.
The LPO measurement was performed using the Bioxytech
LPO-586™ kit (Oxis Research, Portland, USA) and was based
on the reaction of a chromogenic reagent, N-methyl-2-phe-
nylindole with MDA and 4-hydroxyalkenals at 45 °C.
Data are presented as means ? SD. Meat and diet compo-
sitions were analysed by one-way ANOVA. Data were anal-
ysed by a two-factor (time and treatment) repeated-measures
analysis of variance. When there was a significant interaction
time*treatment, the change over time within each group was
assessed by a one-factor ANOVA. The inter-subjects effects of
gender, serum cholesterol, BMI and smoking habit were also
tested. Data were significant at p?0.05. The SPSS 13.0 statis-
tical package was employed.
Table 2. Proximate Composition and Energy Content of
Control Meat (CM) and 20% Walnut-Enriched Meat (WM)
Moisture (g/100g meat)
Energy (kJ/100g meat)
Protein (g/100g meat)
Fat (g/100g meat)
Ash (g/100g meat)
SFA (g/100g total fatty acids)
MUFA (g/100g total fatty acids)
PUFA (g/100g total fatty acids)
?-tocopherol (mg/100g meat)
?-tocopherol (mg/100g meat)
?-tocopherol (mg/100g meat)
Magnesium (mg/100g meat)
1Corresponds to restructured meat and sausages.
SFA ? saturated fatty acids, MUFA ? monounsaturated fatty acids, PUFA ?
polyunsaturated fatty acids.
Adapted from .
Walnuts and Antioxidant Status
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION227
Some details of the diets consumed during both periods are
presented in Table 3. No significant differences were found
between the macronutrients intake in both periods except for
polyunsaturated fatty acid (PUFA), SFA and total tocopherol
Weight and BMI
Body weight was not significantly affected throughout the
CAT. A significant time*treatment interaction on CAT
activity was found (p ? 0.006). During the WM period CAT
activity increased significantly (p ? 0.008) (Table 4). No sig-
nificant differences due to basal serum cholesterol, BMI and
smoking habit were found (data not shown).
SOD. A significant time*treatment interaction was found
(p ? 0.014). SOD changed significantly at the end of both
periods (p ? 0.026) (Table 4). SOD activity was higher at the
end of the intervention period than at the end of the control one
(p ? 0.05). No significant differences related to basal serum
cholesterol, BMI and smoking habit were observed (data not
PON1. A significant time*treatment interaction was found
(p ? 0.005). It significantly increased during the walnut meat-
period but decreased during the control-meat one (p ? 0.05)
(Table 4). No significant differences on PON1 activity due to
serum basal cholesterol, BMI and smoking habit were found
(data not shown).
Total Glutathione. A significant time*treatment interac-
tion was found (p ? 0.018), increasing more during the inter-
vention period than during the control one (Table 4). A triple
gender*time*treatment interaction (p ? 0.043) was found (Fig.
1). Men increased total glutathione following the WM but
women were not significantly affected. Smoking affected neg-
atively (p ? 0.043) the total glutathione concentration (data not
GSH. A significant time*treatment interaction was found
(p ? 0.038). GSH concentrations were significantly higher at
the end of the WM period than at the end of the CM counterpart
(Table 4). Basal concentrations of GSH were higher in non-
smokers (p ? 0.05) (Fig. 2).
GSSG. A significant time*treatment interaction was found
(p ? 0.013). GSSG increased significantly due to treatment
(p ? 0.002) and time (p ? 0.001). Activity was more increased
(p ? 0.05) at the end of the intervention period (Table 4). No
significant differences related to serum basal cholesterol, BMI
and smoking habits were found (data not shown).
Uric Acid. No significant time or treatment effects were
found (Table 4). A significant interaction treatment*BMI was
found (p ? 0.002) as uric acid concentrations of obese volun-
teers increased during the control-meat period more than during
the intervention period. A triple interaction serum cholesterol
levels*time*treatment was found (p ? 0.037). In normocholes-
terolemics but not in hypercholesterolemics, uric acid signifi-
cantly increased during the walnut-meat period and decreased
during the control-meat period (p ? 0.05) (data not shown).
LPO. LPO concentrations did not change throughout the
This study should be considered the first to evaluate the
effect of the intake of WM on oxidative stress in subjects at
high risk of developing CHD. WM should be considered as
functional foods because they have satisfactorily demonstrated
to affect beneficially one or more target functions in the body,
beyond adequate nutritional effects in a way which is relevant
to either the state of well-being and health or the reduction of
the risk of a disease .
Dietary Assessment, Body Weight and BMI
The addition of nuts, very rich in PUFA , to the restruc-
tured meat explains the higher PUFA consumption during the
intervention period with respect to the control period. As in
other studies, where fat contribution to total energy was lower,
equal or higher than 30% [1, 17, 30–32], body weight was not
affected by WM consumption. These results are interesting,
taking into account both the high fat and energy contents of
Table 3. Daily Energy Intake of Macronutrients and Fatty
Acid Energy Contribution during Walnut-Enriched Meat
(WM) and Control Meat (CM) Periods
Guidelines*WM period CM period
Carbohydrates (% En)
Protein (% En)
Fat (% En)
SFA (% En)
MUFA (% En)
PUFA (% En)
Alcohol (% En)
Retinol equivalents (?g)
Total Tocopherols (mg)
Vitamin C (mg)
7721 ? 1244 7419 ? 1202
30.1 ? 7.9
18.4 ? 3.1
47.3 ? 6.9a
12.6 ? 2.8a
19.2 ? 4.8
13.0 ? 2.7a
371 ? 152.1
13.4 ? 5.8
1.7 ? 3.7
668 ? 473
15.4 ? 2.9a
124 ? 95.7
32.5 ? 5.7
19.1 ? 3.3
40.3 ? 7.6b
16.2 ? 5.9b
19.9 ? 6.1
7.2 ? 3.5b
360 ? 136.1
13.4 ? 4.7
1.1 ? 2.4
585 ? 212
9.0 ? 3.8b
107 ? 94.4
SFA ? saturated fatty acids, MUFA ? monounsaturated fatty acids, PUFA ?
polyunsaturated fatty acids.
Data (Mean ? SD) of 22 volunteers bearing different letter were significantly
different (One way ANOVA, p ? 0.05).
*Guidelines for the Spanish population .
Walnuts and Antioxidant Status
228VOL. 26, NO. 3
walnuts , and therefore their potential effect on body weight.
According to Garcı ´a-Lorda et al.  there are three possible
reasons that body weight is not affected by nut consumption (i)
incomplete absorption of energy from nuts, related to the struc-
ture of lipid-storing granules in nuts or to various nut fiber
components, (ii) satiating effect of the dietary fiber in nuts, and
(iii) effect on energy metabolism, probably related to polyphe-
nols, that compensates for the increase in energy availability.
Present data clearly show that the intake of WM 5 times per
week for 5 weeks increased concentrations/activities of several
antioxidant defense biomarkers, such as CAT, SOD, PON1,
total glutathione, GSH and GSSG in study volunteers. Natural
defense against ROS involves a number of enzymatic and non
enzymatic antioxidant mechanisms . The particular com-
position of walnuts, which are rich in antioxidant compounds
such as retinol, ?-carotenes, vitamin E, ?-tocopherol, ?-to-
copherol, ?-tocopherol, folic acid and vitamin C [6, 34], seems
to be responsible for improving the antioxidant status of study
participants. In the present paper, the intake of the WM sup-
plies approximately 29 mg of ?-tocopherol/week  and
increased ?-tocopherol levels by a 8.9% (IC95%?10–16.8%)
. The same authors  observed an increase of vitamin E
(? and ?-tocopherols) in serum and triglyceride-rich lipopro-
teins, suggesting a good bioavailability of vitamin E from WM
Table 4. Effect of WM Treatment on Body Mass Index (BMI), Catalase (CAT), Superoxide Dismutase (SOD), Paraoxonase
(PON1) Activities, Total glutathione, reduced glutathione (GSH), Oxidized Glutathione (GSSG), GSH/GSSG Ratio, Uric Acid
and lipid Peroxidation (LPO) Levels
WM period CM period ANOVA repeated measures
MeanSD Mean SDMeanSD MeanSDTreatment Time
CAT (IU/g Hb)
SOD (IU/g Hb)
Total Glutathione (?mol/g Hb)
GSH (?mol/g Hb)
GSSG (?mol/g Hb)
Uric acid (mg/dL)
Data are Mean ? SD of 22 volunteers. Repeated measures ANOVA followed by posthoc study. Data in the same row bearing a different letter are significantly different
(p ? 0.05).
Fig. 1. Effect of gender and treatment on total glutathione concentra-
tions (?mol/g Hb). Repeated measures ANOVA followed by posthoc
study. Data in the same row bearing a different letter were significantly
different (p ? 0.05).
Fig. 2. Effect of smoking and treatment on reduced glutathione (GSH)
concentrations (?mol/g Hb). Repeated measures ANOVA followed by
posthoc study. Data in the same row bearing a different letter were
significantly different (p ? 0.05).
Walnuts and Antioxidant Status
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 229
in humans. ROS can stimulate oxidation of LDL and oxidized-
LDL (ox-LDL), which is not recognized by apolipoprotein
B100-LDL receptors. Thus, ox-LDL can be taken up by the
scavenger receptors in macrophages, leading to foam cell and
atherosclerotic plaque formation [15, 36]. Recently, a walnut
extract containing ellagic acid, gallic acid and flavonoids was
reported to inhibit oxidation of human plasma and LDL .
Fukuda et al.  analyzed the antioxidant effects of polyphe-
nols from walnuts comparing the action of these antioxidants
with that of others, such as ascorbic acid. After analyzing SOD
activity and other parameters, these authors concluded that
ellagitannin polyphenols from walnuts may act as potent anti-
oxidants. The potential ability of vitamin E to help prevent
CHD deserves special attention. Sabate  reported that a
regular consumption of nuts lowers the risk of myocardial
infarction and death from ischemic heart disease. In animal
studies, ?-tocopherol supplementation increased SOD activity
more than ?-tocopherol supplementation . Nonetheless,
walnuts contain PUFA that are susceptible to oxidation, and the
resulting products could be potentially cytotoxic . To date,
several studies have been conducted in order to test the effect
of lipids on oxidative damage .
The intake of WM increased PON1 activity independently
of HDL-C levels. The HDL-C concentrations were not affected
by the treatment corroborating results of other studies ,
although Tapsell et al.  found that HDL-C increases in type
2 Diabetes patients consuming walnuts in the framework of a
low-fat modified-fat diet. The lack of correlation between
PON1 and HDL-C between volunteers could be due to the
presence of different PON1 polymorphism. Thus, PON1-192R
hydrolyzes paraoxon faster and diazoxon, soman and serin
slower than PON1-192Q . In addition, the ability of HDL
to protect LDL against peroxidation in vitro is reduced signif-
icantly in HDL particles containing PON1-192R with respect to
PON1-192Q . The increase in PON1 concentrations would
be a consequence of the intake of a relatively high amount of
PUFA, counterbalanced by the consumption of nut antioxi-
dants. Many other authors have investigated the influence of
diet on PON1 activity but available results are controversial.
Sutherland et al.  reported that PON1 activity decreases
when the diet contains oil which has been used repeatedly for
frying. The same result was observed in rabbits consuming
atherogenic diets . On the other hand, Kudchodkar et al.
 have observed that PON1 activity is higher in rats con-
suming olive oil than in those with an intake of saturated oil or
fish oils. Although intake of antioxidants may be thought to
favor PON1 status, present data remain inconclusive, as sup-
plementation with vitamin C and E seems to increase PON1
activity , while intake of vegetables, rich in antioxidants,
reduces it . This suggests that PON1 would be more active
in the absence of antioxidants. For this reason, this enzyme
would not be expressed in vegetarians, who consume large
amounts of antioxidants and therefore do not need high activity
of this enzyme.
Due to a large percentage of volunteers were mildly hyper-
cholesterolemics, it can be assumed that the group as a whole
displayed an impaired GSH profile. Simon et al.  and
Yalcin et al.  suggested that the resistance of erythrocytes
to oxidative stress decreases in hypercholesterolemic individ-
uals. The GSH/GSSG ratio is considered as a marker of oxi-
dative stress. As a consequence of higher PUFA intake during
the WM period the GSH/GSSG ratio was higher than during all
the CM period. This data seem controversial having into ac-
count the general improvement of the antioxidant status found
in the present paper, but it has been proposed that some
substrates promote the so called “hormesis” property to induce
a potent antioxidant defense increase after producing relatively
small peroxidation  Moreover, the elevation of microsomal
and cytosolic glutathione S-transferase activities proved the
utilization of GSH in the formation of glutathione S-conjugates.
Due to this, it can be hypothesized that a suitable amount of
GSH would be metabolically used by the glutathione S-trans-
ferases, and the increase in the GSH level could be lower than
In agreement with Du ¨nken et al. , basal concentrations
of GSH (Fig. 2) and total glutathione were significantly lower
in smokers than in non smokers. Although only 18% of the
participants of the present study were smokers, in general we
observed a more positive response in smokers than in non-
smokers, because GSH basal differences due to smoking habit
disappear, suggesting that nut consumption counterbalance the
oxidative stress induced by numerous free radical compounds
present in the gas phase .
Although information suggests that beef consumption in-
creases uric acid in hypercholesterolemics  present results
suggest that uric acid was not affected throughout the whole
study and that the walnut inclusion in meat prevents the obese
volunteers from the increase of uric acid after consuming high
amount of meat .
The consumption of WM induced a decrease of ?34% LPO
concentration in erythrocytes while that of the CM approxi-
mately ?8%. These results suggest that the lipid peroxidation
is not increased by WM consumption despite its higher PUFA
content. Haque et al  found that the aqueous extract of
walnut reduced in mice the LPO content in liver and kidney
induced by chemotherapy toxicity.
The intake of WM 5 times a week for a period of 5 weeks,
in the framework of a fat-rich diet, improved the antioxidant
status of volunteers without inducing changes in the BMI.
Funds for this study were granted by the Spanish Ministerio
de Educacio ´n y Ciencia, Project AGL 2001-2398-C03 and
Walnuts and Antioxidant Status
230 VOL. 26, NO. 3
AGL 2005-07204-C02-01/ALI. Thanks are due to the Univer-
sidad Complutense of Madrid for the predoctoral fellowship of
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Received April 20, 2006; Accepted September 16, 2006
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