Effect of Nut Consumption on Erectile and Sexual Function in Healthy Males: A Secondary Outcome Analysis of the FERTINUTS Randomized Controlled Trial

Abstract

Lifestyle risk factors for erectile and sexual function include smoking, excessive alcohol consumption, lack of physical activity, psychological stress, and adherence to unhealthy diets. In the present study, we evaluated the effects of mixed nuts supplementation on erectile and sexual function. Eighty-three healthy male aged 18-35 with erectile function assessment were included in this FERTINUTS study sub-analysis; a 14-week randomized, controlled, parallel feeding trial. Participants were allocated to (1) the usual Western-style diet enriched with 60 g/day of a mixture of nuts (nut group; n = 43), or (2) the usual Western-style diet avoiding nuts (control group; n = 40). At baseline and the end of the intervention, participants answered 15 questions contained in the validated International Index of Erectile Function (IIEF), and peripheral levels of nitric oxide (NO) and E-selectin were measured, as surrogated markers of erectile endothelial function. Anthropometrical characteristics, and seminogram and blood biochemical parameters did not differ between intervention groups at baseline. Compared to the control group, a significant increase in the orgasmic function (p-value = 0.037) and sexual desire (p-value = 0.040) was observed during the nut intervention. No significant differences in changes between groups were shown in peripheral concentrations of NO and E-selectin. Including nuts in a regular diet significantly improved auto-reported orgasmic function and sexual desire.

Full text

nutrients
Article
Effect of Nut Consumption on Erectile and Sexual
Function in Healthy Males: A Secondary Outcome
Analysis of the FERTINUTS Randomized
Controlled Trial
Albert Salas-Huetos 1,2,3,†, Jananee Muralidharan 1,2, Serena Galiè1,2,
Jordi Salas-Salvadó1,2,3,4,* and Mònica Bulló1,2,3,*
1Human Nutrition Unit, Biochemistry and Biotechnology Department, Faculty of Medicine and Health
Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Spain; albert.salas@utah.edu (A.S.-H.);
jananee.muralidharan@estudiants.urv.cat (J.M.); serena.galie@outlook.it (S.G.)
2Institut d’InvestigacióSanitària Pere i Virgili (IISPV), 43204 Reus, Spain
3Consorcio CIBER, M.P., Physiopathology of Obesity and Nutrition (CIBERobn), Instituto de Salud Carlos
III (ISCIII), 28029 Madrid, Spain
4Hospital Universitari Sant Joan de Reus (HUSJR), 43204 Reus, Spain
*Correspondence: jordi.salas@urv.cat (J.S.-S.); monica.bullo@urv.cat (M.B.);
Tel.: +34-977-75-93-12 (J.S.-S. & M.B.); Fax: +34-977-75-93-22 (J.S.-S. & M.B.)
†
Current affiliation: Andrology and IVF Laboratory, Division of Urology, Department of Surgery, University
of Utah, Salt Lake City, UT 84180, USA.
Received: 8 May 2019; Accepted: 17 June 2019; Published: 19 June 2019


Abstract:
Lifestyle risk factors for erectile and sexual function include smoking, excessive alcohol
consumption, lack of physical activity, psychological stress, and adherence to unhealthy diets.
In the present study, we evaluated the effects of mixed nuts supplementation on erectile and sexual
function. Eighty-three healthy male aged 18–35 with erectile function assessment were included
in this FERTINUTS study sub-analysis; a 14-week randomized, controlled, parallel feeding trial.
Participants were allocated to (1) the usual Western-style diet enriched with 60 g/day of a mixture of
nuts (nut group; n=43), or (2) the usual Western-style diet avoiding nuts (control group; n=40).
At baseline and the end of the intervention, participants answered 15 questions contained in the
validated International Index of Erectile Function (IIEF), and peripheral levels of nitric oxide (NO) and
E-selectin were measured, as surrogated markers of erectile endothelial function. Anthropometrical
characteristics, and seminogram and blood biochemical parameters did not differ between intervention
groups at baseline. Compared to the control group, a significant increase in the orgasmic function
(p-value =0.037) and sexual desire (p-value =0.040) was observed during the nut intervention.
No significant differences in changes between groups were shown in peripheral concentrations of
NO and E-selectin. Including nuts in a regular diet significantly improved auto-reported orgasmic
function and sexual desire.
Keywords: nuts; RCT; erectile function; sexual desire; orgasmic function; nitric oxide; E-selectin
1. Introduction
National Institutes of Health (NIH) define erectile dysfunction (ED) as a persistent difficulty
achieving and maintaining an erection sufficient for satisfactory sexual intercourse [
1
]. The prevalence
of ED ranged from 2% in men younger than 40 years old, around 52% in men aged 40–70 years, and
more than 85% in men with 80 years and older [
2
,
3
]. Although significant advances in the field were
made, primary prevention research on this condition is very preliminary. Lifestyle risk factors for
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Nutrients 2019,11, 1372 2 of 13
ED include smoking, excessive alcohol consumption, lack of physical activity, psychological stress,
overweight or obesity, and adherence to unhealthy diets, among others [4–7].
Lifestyle factors may influence ED through the vascular and nervous system. Because adequate
arterial supply is critical for erection, any disorder that impairs blood flow may be implicated in the
etiology of erectile failure. However, a wide variety of psychological problems can influence the
male erectile response because, in a vascular event initiated by neuronal action, it is maintained by a
complex interplay between vascular, neurological events and other comorbidities [
7
,
8
]. Moreover, it is
generally accepted that nitric oxide (NO) is the principal agent responsible for relaxation/erection of
penile smooth muscle.
Mediterranean diet and some components of the Mediterranean diet have been inversely related
to erectile and sexual dysfunction [
9
] but also a better endothelial function [
10
]. This is the case of
nuts that its consumption has consistently demonstrated beneficial effects on endothelial function [
11
].
In fact, in a recent study, it has demonstrated that pistachio consumption improves erectile function,
probably because it contains (as other types of nuts [
12
]) several antioxidants, and arginine, a precursor
of nitric oxide (NO), a powerful compound that increases vasodilatation [13].
To demonstrate that a dietary pattern or a food group can not only modulate the erectile function,
but also the sperm function increasing the chances of fertility is of great interest mainly in developed
countries where male infertility seems to have fallen drastically [
14
], and the psychological stress seems
to be more prevalent [15].
Therefore, in order to elucidate the possible role of nut consumption in the primary prevention of
ED, we explored using a randomized controlled trial (RCT), the effects of nuts supplementation on
erectile function determined by the International Index of Erectile Function, but also the endothelial
function by measuring peripheral concentrations of NO and E-selectin.
2. Materials and Methods
2.1. Study Design
The study design of the FERTINUTS trial has been reported previously [
16
]. The trial was
registered in ISRCTN registry with identifier ISRCTN12857940. Briefly, FERTINUTS was a 14-week
(wk) randomized, controlled, two-interventions parallel, clinical trial conducted in healthy males
who reported a Western-style diet. The trial was conducted between 2015 and 2017, and included
participants who were randomly assigned (1:1) to one of the following two interventions: (1) enriching
the usual Western-style diet with 60 g/d of a mixture of raw walnuts, almonds, and hazelnuts (nut
group); or (2) following the usual Western-style diet avoiding nuts (control group). The protocol was
approved by the Institutional Review Board of the Hospital Universitari Sant Joan de Reus in October
2015. All the participants provided a written informed consent.
Eligible participants were healthy men aged 18–35 years old. The following exclusion criteria
were applied: frequent consumption of nuts or a known history of allergy; use of plant sterol or fish oil
supplements and multivitamins, vitamin E or other antioxidant supplements; history of reproductive
disorders or vasectomy; current smokers; medications for chronic illness consumption; or use of illegal
drugs. More detailed criteria for enrolment have been reported elsewhere [16].
The effect of the interventions on several cardiovascular risk factors and sperm parameters have
been reported previously [
16
–
18
]. We report here the effect of the interventions on auto-reported
erectile function parameters and the concentrations of peripheral endothelial biomarkers over 14-wk
as a secondary outcome.
2.2. Anthropometric, Dietary, Blood Parameters, and Seminogram Measurements
Trained nurses, biologists, or dietitians directly recall all the general participants’ information and
conduct anthropometric measurements. The initial assessment of individuals was conducted with
a 15-item dietary screener modified from Mart
í
nez-Gonz
á
lez et al., 2012 [
19
] to verify the presence

Nutrients 2019,11, 1372 3 of 13
of a Western-style diet adherence. Participants in the nut group received at no cost, every month,
pre-weighed packs for the consumption of 60 g of nuts per day (30 g of walnuts, 15 g of almonds,
and 15 g of hazelnuts). Participants in both groups received detailed dietary instructions in order to
increase the adherence to the assigned intervention.
At baseline, participants completed a general questionnaire with a medical history, reproductive
history, use of medication, and a 143-item semi-quantitative validated food frequency questionnaire
(FFQ) [20] in a face-to-face interview.
During the 14-wk follow-up (with four in-site visits), weight, height, and waist circumference
were recorded using a high-precision electronic scale (TANITA TBF-300, Tanita). Blood pressure
was measured at rest in duplicate with a 5 minutes interval between each measurement by using
a semiautomatic oscillometer (Omron HEM-705CP, Netherlands). Furthermore, all the participants
completed a specific questionnaire reporting any adverse effects related or not related to the intervention,
and a 3-day dietary record (3DDR) in a face-to-face interview with an expert dietitian in order to
measure the compliance with the dietary intervention. Energy and nutrient intake were calculated
using Spanish food composition tables [
21
,
22
]. Adherence to the intervention was also assessed by
counting the empty sachets of nuts returned in each visit.
At baseline and at the end of the intervention, blood samples in 12 h fasting conditions and semen
samples after 3 days of sexual abstinence were collected. Fasting glucose, total cholesterol, HDL
cholesterol, LDL cholesterol, VLDL cholesterol, triglycerides, insulin, C-reactive protein (CRP), and
folate were determined (COBAS; Roche Diagnostics Ltd, UK) in blood. Semen volume and pH, sperm
count and concentration, sperm motility, sperm viability, and sperm morphology were assessed in
semen following the 2010 WHO criteria and the Björndahl checklist [23,24].
2.3. Erectile Function Questionnaire
The main outcome in the present analysis was the erectile function. To evaluate the influence
of nuts on erectile function, participants answered to the 15 questions contained in the validated
International Index of Erectile Function (IIEF) [
25
] at baseline and the end of the intervention. The
IIEF-15 permits to detect treatment-related changes [
25
,
26
]. The questionnaire of IIEF-15 addresses the
relevant domains of male sexual function: erectile function (EF: 0–6 severe dysfunction, 7–12 moderate
dysfunction, 13–18 mild to moderate dysfunction, 19-24 mild dysfunction, 25–30 no dysfunction),
orgasmic function (OF: 0–2 severe dysfunction, 3-4 moderate dysfunction, 5–6 mild to moderate
dysfunction, 7–8 mild dysfunction, 9–10 no dysfunction), sexual desire (SD: 0–2 severe dysfunction, 3–4
moderate dysfunction, 5–6 mild to moderate dysfunction, 7–8 mild dysfunction, 9–10 no dysfunction),
intercourse satisfaction (IS: 0–3 severe dysfunction, 4–6 moderate dysfunction, 7–9 mild to moderate
dysfunction, 10–12 mild dysfunction, 13–15 no dysfunction), and overall satisfaction (OS: 0–2 severe
dysfunction, 3–4 moderate dysfunction, 5–6 mild to moderate dysfunction, 7–8 mild dysfunction,
9–10 no dysfunction).
2.4. Surrogated Measures of Erectile Endothelial Function
At baseline and end of the trial the peripheral concentrations of endothelial function markers, NO
and E-selectin, were measured by Enzyme-Linked Immunosorbent Assay (ELISA) procedures according
to the manufacturer instructions. Briefly, the NO assay kit (ThermoFisher Scientific) determines nitric
oxide composition through measurement of nitrate (NO
3
) and nitrite (NO
2
) levels, while the E-selectin
assay kit (ThermoFisher Scientific) determines the soluble E-selectin. Samples were read at 540 nm
absorbance in the case of NO assay, and 450 nm absorbance in the case of E-selectin assay (TECAN,
Sunrise). A polynomial curve was used as the standard. Laboratory technicians were blinded to
group assignments.

Nutrients 2019,11, 1372 4 of 13
2.5. Statistical Analyses
The sample size for the FERTINUTS trial was calculated to detect significant differences in the
viability after nut consumption based on the results of Robbins et al., 2012 [
27
]. However, taking
into account EF changes reported in a previous similar trial [
9
], a total sample size of 54 (27 per
arm) was estimated to provide sufficient statistical power (more than 80%) to assess the effects of nut
supplementation on erectile function parameters assuming two-sided 95% confidence interval.
Kolmogorov–Smirnov and Levene’s test were used in order to check the normal distribution
and homogeneity, respectively. The data are shown as means
±
standard deviation (SD) for normally
distributed variables, and median
±
interquartile rank (IQR) for non-normal continuous variables.
Non-parametric statistical Mann–Whitney for non-paired data and Wilcoxon tests for paired data
were used to assess differences within each intervention. ANCOVA models were applied to assess
differences in changes between intervention groups after adjusting for baseline values. Spearman
correlation coefficients were used to calculate pair-wise correlations, and Benjamini-Hochberg false
discovery rate (FDR) correction was used for multiple comparisons. Statistical analyses were conducted
using per protocol approaches, including all randomized participants fulfilling all baseline and final
measurements. p-values of <0.05 were considered statistically significant. Statistical analyses were
carried out using the freely available R statistical computing environment v.2.14.2 (www.r-project.
org) [28] and the additional package Deducer for R (http://www.deducer.org/) [29].
3. Results
In the FERTINUTS trial, we assessed 244 subjects for eligibility. Of these, 57 subjects declined to
participate and 68 did not meet the inclusion criteria. Thus, 119 participants were included in the trial
and were randomly assigned to one of the two intervention groups: 61 in the nuts group and 58 in the
control group. A total 98 participants successfully completed the study, and finally, 83 participants
were included in this secondary analysis (those subjects who fulfilled the International Index of Erectile
Function questionnaire): 43 in the nuts supplemented group and 40 in the control group (Figure 1).
Baseline characteristics (age, weight, height, BMI, waist circumference, systolic and diastolic blood
pressure, fasting glucose, serum total cholesterol, HDL cholesterol, LDL cholesterol, VLDL cholesterol,
triglycerides, insulin, C-reactive protein and folate, and main sperm parameters) are detailed in Table 1.
No significant differences were observed in these baseline parameters agreeing to the sequence of
randomization. Participants in the two groups reported similar adherence to the Western-style diet at
baseline according to the 15-item dietary screener.
Compliance with the intervention, as assessed by counting the empty sachets of nuts returned
by the participants, was high (>95% of empty sachets returned). According to the 3DDR data,
significant between-group differences in nut intake was shown through the study. This was
associated with an increase in the intake total fat (p-value <0.001), MUFA (p-value<0.001), PUFA
(p-value <0.001), magnesium (p-value <0.001), vitamin E (p-value =0.014), omega-3 fatty acids
(p-value <0.001),
α
-Linolenic acid (ALA) (p-value <0.001), and omega-6 fatty acids (p-value =0.016)
in the nut-supplemented group. The intake of energy (p-value =0.029) and fiber (p-value =0.002)
experienced a smaller decrease in the nut-supplemented group compared with the control group
(Table 2).

Nutrients 2019,11, 1372 5 of 13
Nutrients 2018, 10, x FOR PEER REVIEW 5 of 14
Figure 1. Flow diagram of the FERTINUTS sub-analysis. * 68 participants did not meet the
inclusion criteria (ascribed to a non-Western style diet, n = 37; smoking, n = 21; or other
minor reasons, n = 10) and 57 subjects declined to participate (lack of interest, n = 34;
impossible to contact with them, n = 18; and for non-economic compensation, n = 5).
Baseline characteristics (age, weight, height, BMI, waist circumference, systolic and diastolic
blood pressure, fasting glucose, serum total cholesterol, HDL cholesterol, LDL cholesterol, VLDL
cholesterol, triglycerides, insulin, C-reactive protein and folate, and main sperm parameters) are
detailed in Table 1. No significant differences were observed in these baseline parameters agreeing
to the sequence of randomization. Participants in the two groups reported similar adherence to the
Western-style diet at baseline according to the 15-item dietary screener.
Table 1. Baseline characteristics of the study population (general characteristics, blood, and
semen parameters).
Variable
Nuts Group (n = 43)
Control Group (n = 40)
P-Value
General characteristics; mean (SD)
Age (years)
24.05 (4.82)
25.83 (4.58)
0.066
Weight (kg)
73.44 (10.16)
76.82 (12.04)
0.270
Height (cm)
176.46 (6.21)
177.73 (6.66)
0.409
BMI (kg/m2)
23.53 (2.59)
24.33 (3.64)
0.379
Figure 1.
Flow diagram of the FERTINUTS sub-analysis. * 68 participants did not meet the inclusion
criteria (ascribed to a non-Western style diet, n=37; smoking, n=21; or other minor reasons, n=10)
and 57 subjects declined to participate (lack of interest, n=34; impossible to contact with them, n=18;
and for non-economic compensation, n=5).

Nutrients 2019,11, 1372 6 of 13
Table 1.
Baseline characteristics of the study population (general characteristics, blood, and
semen parameters).
Variable Nuts Group (n=43) Control Group (n=40) p-Value
General characteristics; mean
(SD)
Age (years) 24.05 (4.82) 25.83 (4.58) 0.066
Weight (kg) 73.44 (10.16) 76.82 (12.04) 0.270
Height (cm) 176.46 (6.21) 177.73 (6.66) 0.409
BMI (kg/m2)23.53 (2.59) 24.33 (3.64) 0.379
Waist circumference (cm) 79.98 (7.41) 83.26 (8.98) 0.067
Systolic blood pressure (mmHg)
129.38 (11.37) 126.50 (11.79) 0.425
Diastolic blood pressure
(mmHg) 73.34 (7.90) 70.90 (8.49) 0.174
Score for adherence to
Western-style diet a8.11 (2.16) 8.80 (2.26) 0.182
Blood parameters; median (IQR)
Fasting plasma glucose (mg/dl) 87.0 (82.0, 93.5) 85.5 (81.5, 91.0) 0.384
Total cholesterol (mg/dl) 167.0 (149.5, 188.5) 173.5 (150.0, 196.0) 0.374
HDL-c (mg/dl) 58.0 (49.5, 66.5) 55.5 (50.0, 67.0) 0.736
LDL-c (mg/dl) 87.0 (74.5, 105.5) 98.0 (77.8, 119.3) 0.202
VLDL-c (mg/dl) 13.0 (12.0, 19.0) 13.0 (9.0, 17.3) 0.240
Triglycerides (mg/dl) 66.0 (59.0, 95.5) 64.0 (47.0, 85.0) 0.258
Fasting plasma insulin
(mcUl/ml) 5.40 (2.60, 8.60) 5.20 (2.75, 6.80) 0.654
C-Reactive protein (mg/dl) 0.20 (0.20, 0.20) 0.20 (0.13, 0.20) 0.144
Folate (ng/ml) 6.30 (4.80, 8.70) 6.30 (4.88, 7.80) 0.616
Semen characteristics; median
(IQR)
pH 8.0 (8.0, 8.5) 8.0 (8.0, 8.5) 0.940
Volume (mL) 3.50 (1.95, 4.55) 3.40 (2.50, 5.13) 0.179
Total spermatozoa (×106)75.20 (28.10, 104.50) 72.05 (40.90, 125.50) 0.497
Spermatozoa concentration
(×106)25.20 (14.50, 41.80) 19.80 (9.70, 37.95) 0.402
Viability (%) 78.68 (70.26, 82.52) 80.21 (73.66, 85.87) 0.257
Total motility (progressive and
non-progressive motility) (%) 64.66 (45.91, 71.34) 70.11 (62.73, 78.56) 0.097
Progressive motility (%) 44.67 (28.27, 53.97) 49.72 (35.39, 61.67) 0.086
Non-progressive motility (%) 13.26 (9.79, 16.15) 11.64 (7.58, 14.31) 0.103
Immotile spermatozoa (%) 35.33 (28.58, 52.06) 29.89 (21.44, 37.27) 0.094
Normal forms (%) 6.33 (4.91, 8.17) 6.27 (5.23, 7.57) 0.935
Abnormal head (%) 52.59 (43.06, 66.28) 55.07 (41.22, 67.81) 0.771
Abnormal midpiece (%) 10.71 (8.63, 15.05) 12.71 (8.46, 14.23) 0.705
Abnormal principal piece (%) 12.94 (5.44, 29.66) 9.46 (4.53, 25.27) 0.529
Combined abnormality (%) 8.40 (6.49, 12.88) 7.85 (6.71, 14.07) 0.985
Data are given as mean and standard deviation (SD) or medians and Interquartile ranges (IQRs). All the
analyses were assessed by non-parametric tests (the Mann–Whitney for non-paired data) for normality distribution
reasons. Equivalences: 1 mg/dl plasma glucose =18.018 mmol/l, 1 mg/dl total cholesterol=38.610 mmol/l.
a
The score for adherence to the Western-style diet is based on a 15-item dietary screener (a score of zero indicates
minimum adherence, a score of 15 indicates maximum adherence). Abbreviations: BMI, body mass index; HDL,
high-density lipoprotein; IQR, interquartile rank; LDL, low-density lipoprotein; SD, standard deviation; VLDL,
very-low-density lipoprotein.

Nutrients 2019,11, 1372 7 of 13
Table 2. Nutrient intake at baseline and changes by intervention group.
Variables Nut Group (n=43) Control Group (n=40) Treatment Effect
Baseline Changes Baseline Changes p-Value
Energy
Energy intake
(kcal/d)
2699.13 (994.43)
−145.19 (31.74)
2359.57 (565.72)
−215.22 (18.18) 0.029
Macronutrients
Proteins (g/d) 112.20 (39.37) −7.68 (1.44) 103.13 (22.51) −10.45 (0.34) 0.065
Carbohydrates
(g/d) 305.24 (134.16) −50.48 (4.83) 254.34 (63.04) −11.21 (0.05) 0.333
Simple
carbohydrates (g/d)
112.70 (79.80) −13.47 (3.33) 92.54 (28.75) −6.31 (0.06) 0.696
Complex
carbohydrates (g/d)
176.44 (68.26) −34.36 (0.84) 145.29 (46.70) −12.09 (1.30) 0.604
Total fat (g/d) 106.89 (40.75) 12.19 (0.66) 97.98 (30.47) −11.95 (0.92) <0.001
MUFA (g/d) 42.87 (18.36) 5.89 (0.32) 37.97 (15.82) −6.14 (0.48) <0.001
SFA (g/d) 33.33 (17.87) −3.19 (0.21) 31.17 (10.64) −3.67 (0.04) 0.589
PUFA (g/d) 13.51 (6.41) 11.03 (0.27) 11.37 (4.50) −2.60 (0.23) <0.001
Cholesterol (mg/d) 426.64 (253.96) −70.48 (8.95) 386.09 (131.85) −56.08 (2.37) 0.745
Fiber (g/d) 24.69 (11.21) −0.77 (0.39) 19.84 (9.45) −2.39 (0.41) 0.002
Alcohol (g/d) 9.43 (14.01) −2.79 (0.73) 7.91 (13.14) −2.25 (0.89) 0.693
Glycemic load 172.69 (75.43) −31.38 (2.55) 141.20 (37.69) −5.52 (0.32) 0.384
Glycemic index 56.16 (4.50) −1.48 (0.18) 55.13 (5.45) 0.29 (0.08) 0.346
Micronutrients
Sodium (mg/d) 3452.88
(1455.36) −407.37 (26.13)
3178.08 (958.75)
−174.95 (23.37) 0.743
Potassium (mg/d) 3639.91
(1624.75) −217.88 (58.80)
3126.17 (968.16)
−140.77 (21.62) 0.289
Linoleic (g/d) 26.08 (26.64) 4.79 (1.35) 31.40 (31.79) −4.66 (1.24) 0.311
Magnesium (mg/d)
407.62 (199.96) 32.17 (7.96) 329.53 (108.61) −16.92 (0.93) <0.001
Calcium (mg/d) 987.45 (514.83) −98.27 (2.79) 898.70 (324.53) −51.64 (13.16) 0.843
Iron (mg/d) 20.27 (14.55) −2.04 (0.60) 18.35 (13.33) −0.11 (0.47) 0.864
Selenium (mg/d) 222.04 (162.30) −48.94 (13.01) 209.25 (140.86) −46.06 (11.51) 0.563
β-carotene
equivalents (µg/d)
4711.11
(5096.91)
−1008.75
(348.71)
3913.42
(4116.64) 22.34 (72.89) 0.642
Retinol (µg/d)
592.05 (1409.67)
−230.55
(169.57) 402.76 (166.28) 141.07 (141.29) 0.254
Vitamin D (µg/d) 7.37 (13.90) 0.55 (0.31) 5.05 (5.65) 4.50 (3.67) 0.606
Vitamin E (µg/d) 13.18 (5.12) 6.10 (1.20) 15.19 (18.38) −3.03 (0.93) 0.014
Vitamin K (µg/d) 130.94 (163.71) −10.50 (0.30) 115.38 (111.22) −32.51 (6.99) 0.213
Omega-3 (g/d) 1.72 (0.89) 1.53 (0.02) 1.68 (0.73) −0.10 (0.02) <0.001
ALA (g/d) 1.10 (0.61) 1.55 (0.02) 1.00 (0.39) −0.22 (0.02) <0.001
EPA (g/d) 0.51 (2.74) 0.02 (0.00) 1.03 (3.96) 0.65 (0.12) 0.236
DHA (g/d) 0.15 (0.19) 0.02 (0.01) 0.21 (0.31) 0.10 (0.03) 0.161
Omega-6 (g/d) 18.03 (14.80) 10.27 (0.08) 24.64 (23.36) −3.76 (0.94) 0.016
Dataare given as meansand SD for baselinevalues, and mean and SE for changes. Inbold the significant values. ANCOVA
models were used to assess differences between intervention groups. Changes in variables were adjusted for baseline
values of each variable. Abbreviations: ALA:
α
-Linolenic acid, DHA: docosahexaenoic acid, EPA: eicosapentaenoic acid,
MUFA: monounsaturated fatty acids, PUFA: polyunsaturated fatty acids, SFA: saturated fatty acids.
No significant between-group differences were observed in erectile function parameters at
baseline. However, compared to the control group, a significant increase in the orgasmic function (OF;
p-value =0.037) and sexual desire (SD; p-value =0.040) was observed in the nut-supplemented group
during the intervention. No significant between-group differences in changes during the intervention
were found in erectile function (EF; p-value =0.192), intercourse satisfaction (IS; p-value =0.473), and
overall satisfaction (OS; p-value =0.333) (Figure 2). No significant correlations were found between
changes in ED parameters and changes in biochemical parameters during the intervention.

Nutrients 2019,11, 1372 8 of 13
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Nutrients 2018, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/nutrients
Figure 2. Box plot of the differences between the control group and the nut-supplemented group in the erectile function parameters (IIEF-15). ANCOVA
models were used to assess differences between intervention groups. Changes were adjusted for baseline values. A horizontal line in the boxplot illustrates
the median value. The upper and lower bars indicate the third and first percentiles, respectively. Outliers are plotted as individual circles. Abbreviations:
IIEF: International Index of Erectile Function.
Figure 2.
Box plot of the differences between the control group and the nut-supplemented group in the erectile function parameters (IIEF-15). ANCOVA models were
used to assess differences between intervention groups. Changes were adjusted for baseline values. A horizontal line in the boxplot illustrates the median value.
The upper and lower bars indicate the third and first percentiles, respectively. Outliers are plotted as individual circles. Abbreviations: IIEF: International Index of
Erectile Function.

Nutrients 2019,11, 1372 9 of 13
Moreover, no significant differences in changes between intervention groups were shown in
peripheral concentrations of NO (p-value =0.737) (Figure 3A) or E-selectin (p-value =0.347) (Figure 3B).
Nutrients 2018, 10, x FOR PEER REVIEW 10 of 14
Nutrients 2018, 10, x; doi: FOR PEER REVIEW www.mdpi.com/journal/nutrients
Moreover, no significant differences in changes between intervention groups were shown in
peripheral concentrations of NO (p-value = 0.737) (Figure 3A) or E-selectin (p-value = 0.347) (Figure
3B).
Figure 3. Box plot of the differences between the control group and the nut group in the
concentrations of nitric oxide (A) and E-selectin (B) erectile function markers. ANCOVA
models were used to assess differences between intervention groups. Changes were
adjusted for baseline values. A horizontal line in the boxplot illustrates the median value.
The upper and lower bars indicate the third and first percentiles, respectively. Outliers are
plotted as individual circles. In this analysis 3 participants (2 participants in the nut group
and 1 in the control group) had missing values for NO or E-selectin (see Figure 1).
4. Discussion
Herein we report that adding 60 g/d of mixed raw nuts to a Western-style diet for 14-wk
improved the auto-reported orgasmic function and sexual desire parameters in a group of healthy
reproductive-aged participants compared with an age-matched control group. In the present study,
Figure 3.
Box plot of the differences between the control group and the nut group in the concentrations
of nitric oxide (
A
) and E-selectin (
B
) erectile function markers. ANCOVA models were used to assess
differences between intervention groups. Changes were adjusted for baseline values. A horizontal
line in the boxplot illustrates the median value. The upper and lower bars indicate the third and first
percentiles, respectively. Outliers are plotted as individual circles. In this analysis 3 participants (2
participants in the nut group and 1 in the control group) had missing values for NO or E-selectin (see
Figure 1).
4. Discussion
Herein we report that adding 60 g/d of mixed raw nuts to a Western-style diet for 14-wk
improved the auto-reported orgasmic function and sexual desire parameters in a group of healthy
reproductive-aged participants compared with an age-matched control group. In the present study,

Nutrients 2019,11, 1372 10 of 13
none of the possible mechanisms explored (NO and E-selectin as surrogated markers of endothelial
function) seem to explain the beneficial effects observed on orgasmic function and sexual desire.
Interestingly, our findings in healthy young males are pretty consistent with the only previous
clinical study reporting an increase of all the five IIEF-15 domains after 100 g/day pistachio consumption
for 3 weeks [
13
], although this study was conducted in patients with erectile dysfunction at baseline.
Therefore, our study extends the findings to a healthy population without erectile dysfunction
supplemented with a mixture of nuts like hazelnuts, almonds, and walnuts.
Nuts are nutrient-dense foods with a special nutrient content, a key component of several healthy
dietary patterns and recommendations, and its consumption is associated with improvements in some
cardiovascular disease risk factors [
30
–
32
]. Specifically, hazelnuts, almonds and walnuts contain high
amounts of vegetable protein and fat (mainly unsaturated fatty acids), are dense in antioxidants and
vitamins (e.g., folic acid, niacin, tocopherols, and vitamin B6, among others) and some minerals (e.g.,
calcium, magnesium, phosphorous and potassium), and also rich =in dietary fiber and many other
bioactive constituents (e.g., phytosterols and phenolic compounds) (Supplementary Materials Table
S1 [33]).
In addition, nuts had a relatively high amount of the nonessential amino acid arginine, a
precursor of NO, that is a potent vasoactive neurovascular, nonadrenergic, noncholinergic (NANC)
neurotransmitter that plays an important role in erectile action through the corpora cavernosa [
34
].
The results from our study do not demonstrate that Arginine-NO pathway act as the unique player
modulating erectile function. However, we cannot discard a lack of statistical power to demonstrate
differences between intervention groups in relation to these subrogated markers of endothelial function,
because the sample size of the present sub-analysis was estimated using the IIEF as the main outcome.
Another promising serum biomarker for erectile function is serum E-selectin [
35
]. In that case,
E-selectin, because it is an endothelial dysfunction marker, seems more useful in patients diagnosed
with diabetes mellitus [
36
]. E-selectin is a cell adhesion molecule activated by cytokines that plays an
important role in inflammation. Because consuming between 60 and 90 g of nuts has proven effective
improving inflammation [
37
] it could have been reasonable to detect some differences in this marker
due to the nut’s supplementation. Nonetheless, our study does also not confirm any effect on this
endothelial marker. This lack of effect could be explained not only because of a lack of power but also
because our participants were healthy and therefore without having type 2 diabetes.
Because we detected an improvement in the auto-reported orgasmic function and sexual desire
parameters, maybe other mechanisms beyond those mentioned above may be implicated. It is
interesting to mention that erectile (dys)function and atherogenesis share common pathways [
38
]. For
that reason, several antioxidants (e.g., polyphenols) and vitamins, that are present in nuts, have been
suggested to be effective treatments for ED and at the same time are beneficial for the cardiovascular
system [
38
]. Previous studies reported that chronic consumption of nuts has proven effective for
lowering LDL cholesterol [
32
] and improving glucose metabolism [
39
], among other cardiovascular
risk factors, decreasing the incidence of major cardiovascular events [
17
]. Therefore, we strongly
believe in the necessity to develop similar trials with participants at high cardiovascular risk and
erectile dysfunction to accurately establish an effect of nut consumption on erectile function and
cardiovascular risk.
Our study has several strengths. This is the largest and unique RCT to date analyzing the effect of
nut supplementation on erectile and sexual function in healthy participants. Moreover, the present
analysis has theoretically enough statistical power to detect effects on erectile function measured
by a validated International Index of Erectile Function. Although several questionnaires have been
developed to objectively evaluate EDs, the validated International Index of Erectile Function (IIEF)
questionnaire is considered a valuable tool for defining the area of sexual dysfunction that may be
incorporated as part of the clinical history to document the degree of dysfunction and gauge response
to therapy [
25
]. Moreover, having detailed information on medical and reproductive history allowed
us to reduce bias by excluding participants with chronic and reproductive diseases that may influence

Nutrients 2019,11, 1372 11 of 13
diet, seminogram or erectile function. The main strength of the present study is the design because
RCTs represent the cornerstone of evidence-based medicine.
However, the following limitations need to be highlighted. The present study is based on a
secondary outcome analysis of the FERTINUTS trial. Second, our study was conducted in apparently
healthy and fertile participants limiting the extrapolation of the results to other populations, for example
with erectile dysfunction, the inclusion of a group of subjects suffering from erectile dysfunction could
help us to extend the results obtained. Third, reproductive hormonal (e.g., testosterone, prolactin, FSH,
estradiol) values, which could affect erectile and sexual function are not reported. Finally, our study
did not provide enough evidence to support the main mechanism for these improvements, however,
an absence of evidence does not mean evidence of no effect [
40
]. Only equivalence trials are properly
suited to demonstrate the equality of effects. For that reason, other RCT focused on markers of erectile
endothelial function as possible mechanisms of the effect as main outcomes, are warranted in the future
to increase the scientific evidence in the field.
5. Conclusions
In conclusion, our study suggests that compliance with a healthy diet supplemented with mixed
nuts may help to improve erectile and sexual desire. Large studies are warranted in the future to
confirm these results and elucidate possible mechanisms implicated on these benefits.
Supplementary Materials:
The following are available online at http://www.mdpi.com/2072-6643/11/6/1372/s1,
Table S1: Average nutrient composition of studied nuts (per 100 g).
Author Contributions:
A.S.-H. and J.S.-S. initiated the idea of the trial. A.S.-H., J.S.-S., and M.B. were involved in
study concept and design. A.S.-H. was involved in study execution, acquisition of data, analyzed of data, wrote
the manuscript and had primary responsibility for final content; J.M. and S.G. were involved in erectile function
markers analysis. J.S.-S., and M.B. supervised the analysis and critically revised the manuscript. All authors
provided substantial intellectual contributions and approved the final version of the manuscript.
Funding:
This work was partially supported by the International Nut and Dried Fruit Council (INC) with the
Grant No. 2015 INC Research Grant (PV15110S) and by Human Nutrition Unit funds. INC is a non-profit entity
registered at the Register of Foundations of Catalonia, Spain. Nuts were supplied by Crisolar, Spain.
Acknowledgments:
We thank all the FERTINUTS participants for their enthusiastic collaboration. The authors
gratefully acknowledge Santiago Dom
í
nguez for nursery assistance, Roc
í
o Moraleda for dietary assessment and
some primary data collection, and Susana Benigno and Carles Munn
é
for their help as editor assistance. Consorcio
CIBER, M.P., Physiopathology of Obesity and Nutrition (CIBERobn), Instituto de Salud Carlos III (ISCIII). The Plan
Nacional de Investigaci
ó
n Cient
í
fica, Desarrollo e Innovaci
ó
n Tecnol
ó
gica, the Instituto de Salud Carlos III - Fondo de
Investigación Sanitaria (PI12/0153). The Fondo Europeo de Desarrollo Regional (FEDER).
Conflicts of Interest:
J.S.-S. is a nonpaid member of the Scientific Advisory Council of the INC. M.B. has
received research funds through her Institution from Pistachio Growers. No other potential conflicts of interest
were reported.
References
1.
NIH Consensus NIH Consensus Conference: NIH Consensus Development Panel on Impotence. JAMA
1993,270, 83–90. [CrossRef]
2.
Prins, J.; Blanker, M.H.; Bohnen, A.M.; Thomas, S.; Bosch, J. Prevalence of erectile dysfunction: A systematic
review of population-based studies. Int. J. Impot. Res. 2002,14, 422–432. [CrossRef]
3.
Aytac, I.; McCkinlay, J.; Krane, R. The likely worldwide increase in erectile dysfunction between 1995 and
2025 and some possible policy consequences. BJU Int. 1999,84, 50–56. [CrossRef]
4.
Maiorino, M.; Bellastella, G.; Esposito, K. Lifestyle modifications and erectile dysfunction: What can be
expected? Asian J. Androl. 2015,17, 5–10.
5.
Kirby, M. The circle of lifestyle and erectile dysfunction. Sex. Med. Rev.
2015
,3, 169–182. [CrossRef]
[PubMed]
6.
Hehemann, M.C.; Kashania, J.A. Can lifestyle modification affect men’s erectile function? Transl. Androl.
Urol. 2016,5, 187–194. [CrossRef]

Nutrients 2019,11, 1372 12 of 13
7.
Allen, M.S.; Walter, E.E. Erectile Dysfunction: An Umbrella Review of Meta-Analyses of Risk-Factors,
Treatment, and Prevalence Outcomes. J. Sex. Med. 2019,16, 531–541. [CrossRef]
8.
Vlachopoulos, C.; Rokkas, K.; Ioakeimidis, N. Inflammation, metabolic syndrome, erectile dysfunction, and
coronary artery disease: Common links. Eur. Urol. 2007,52, 1590–1600. [CrossRef] [PubMed]
9.
Esposito, K.; Ciotola, M.; Giugliano, F.; De Sio, M.; Giugliano, G.; D’Armiento, M.; Giugliano, D. Mediterranean
diet improves erectile function in subjects with the metabolic syndrome. Int. J. Impot. Res.
2006
,18, 405–410.
[CrossRef]
10.
Schwingshackl, L.; Hoffmann, G. Mediterranean dietary pattern, inflammation and endothelial function: A
systematic review and meta-analysis of intervention trials. Nutr. Metab. Cardiovasc. Dis.
2014
,24, 929–939.
[CrossRef]
11.
Neale, E.P.; Tapsell, L.C.; Guan, V.; Batterham, M.J. The effect of nut consumption on markers of inflammation
and endothelial function: A systematic review and meta-analysis of randomised controlled trials. BMJ Open
2017,7, e016863. [CrossRef] [PubMed]
12.
Yu, Z.; Malik, V.S.; Keum, N.; Hu, F.B.; Giovannucci, E.L.; Stampfer, M.J.; Willett, W.C.; Fuchs, C.S.; Bao, Y.
Associations between nut consumption and inflammatory biomarkers. Am. J. Clin. Nutr.
2016
,104, 722–728.
[CrossRef] [PubMed]
13.
Aldemir, M.; Okulu, E.; Ne¸selio˘glu, S.; Erel, O.; Kayıgil, Ö. Pistachio diet improves erectile function
parameters and serum lipid profiles in patients with erectile dysfunction. Int. J. Impot. Res.
2011
,23, 32–38.
[CrossRef] [PubMed]
14.
Levine, H.; Jørgensen, N.; Martino-Andrade, A.; Mendiola, J.; Weksler-Derri, D.; Mindlis, I.; Pinotti, R.;
Swan, S.H. Temporal trends in sperm count: A systematic review and meta-regression analysis. Hum. Reprod.
Update 2017,23, 646–659. [CrossRef] [PubMed]
15.
Ilacqua, A.; Izzo, G.; Emerenziani, G.P.; Baldari, C.; Aversa, A. Lifestyle and fertility: The influence of stress
and quality of life on male fertility. Reprod. Biol. Endocrinol. 2018,16, 115. [CrossRef] [PubMed]
16.
Salas-Huetos, A.; Moraleda, R.; Giardina, S.; Anton, E.; Blanco, J.; Salas-Salvad
ó
, J.; Bull
ó
, M. Effect of
nut consumption on semen quality and functionality in healthy men consuming a Western-style diet: A
randomized controlled trial. Am. J. Clin. Nutr. 2018,108, 953–962. [CrossRef] [PubMed]
17.
Estruch, R.; Ros, E.; Salas-Salvad
ó
, J.; Covas, M.-I.; Corella, D.; Ar
ó
s, F.; G
ó
mez-Gracia, E.; Ruiz-Guti
é
rrez, V.;
Fiol, M.; Lapetra, J.; et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet
Supplemented with Extra-Virgin Olive Oil or Nuts. N. Engl. J. Med. 2018,378, e34. [CrossRef] [PubMed]
18.
Salas-Salvad
ó
, J.; D
í
az-L
ó
pez, A.; Ruiz-Canela, M.; Basora, J.; Fit
ó
, M.; Corella, D.; Serra-Majem, L.;
Warnberg, J.; Romaguera, D.; Estruch, R.; et al. Effect of a lifestyle intervention program with energy-restricted
Mediterranean diet and exercise on weight loss and cardiovascular risk factors: One-year results of the
PREDIMED-Plus trial. Diabetes Care 2018,42, 777–788. [CrossRef] [PubMed]
19.
Mart
í
nez-Gonz
á
lez, M.A.; Garc
í
a-Arellano, A.; Toledo, E.; Salas-Salvad
ó
, J.; Buil-Cosiales, P.; Corella, D.;
Covas, M.I.; Schröder, H.; Ar
ó
s, F.; G
ó
mez-Gracia, E.; et al. A 14-item mediterranean diet assessment tool
and obesity indexes among high-risk subjects: The PREDIMED trial. PLoS ONE
2012
,7, e43134. [CrossRef]
[PubMed]
20.
Fern
á
ndez-Ballart, J.D.; Piñol, J.L.; Zazpe, I.; Corella, D.; Carrasco, P.; Toledo, E.; Perez-Bauer, M.;
Mart
í
nez-Gonz
á
lez, M.A.; Salas-Salvad
ó
, J.; Mart
í
n-Moreno, J.M. Relative validity of a semi-quantitative
food-frequency questionnaire in an elderly Mediterranean population of Spain. Br. J. Nutr.
2010
,103,
1808–1816. [CrossRef] [PubMed]
21.
Moreiras, O.; Carvajal, A. Tablas de Composici
ó
n de Alimentos (Food Composition Tables), 9th ed.; Ediciones
Pirámide: Madrid, Spain, 2005.
22.
Mataix Verd
ú
, J. Tabla de Composici
ó
n de Alimentos Españoles (Food Composition Tables), 4th ed.; Universidad de
Granada: Granada, Spain, 2003.
23.
World Health Organization. WHO Laboratory Manual for the Examination and Processing of Human Semen,
5th ed.; World Health Organization: Geneva, Switzerland, 2010.
24.
Björndahl, L.; Barratt, C.L.R.; Mortimer, D.; Jouannet, P. “How to count sperm properly”: Checklist for
acceptability of studies based on human semen analysis. Hum. Reprod.
2016
,31, 227–232. [CrossRef]
[PubMed]

Nutrients 2019,11, 1372 13 of 13
25.
Rosen, R.C.; Riley, A.; Wagner, G.; Osterloh, I.H.; Kirkpatrick, J.; Mishra, A. The international index of erectile
function (IIEF): A multidimensional scale for assessment of erectile dysfunction. Urology
1997
,49, 822–830.
[CrossRef]
26.
Rosen, R.C.; Cappelleri, J.C.; Iii, N.G. The International Index of Erectile Function (IIEF): A state-of-the-science
review. Int. J. Impot. Res. 2002,14, 226–244. [CrossRef] [PubMed]
27.
Robbins, W.A.; Xun, L.; FitzGerald, L.Z.; Esguerra, S.; Henning, S.M.; Carpenter, C.L. Walnuts improve
semen quality in men consuming a Western-style diet: Randomized control dietary intervention trial. Biol.
Reprod. 2012,87, 101–111. [CrossRef] [PubMed]
28.
R Development Core Team. R: A Language and Environment for Statistical Computing; R Foundation for
Statistical Computing: Vienna, Austria, 2013; ISBN 3-900051-07-0. Available online: http://www.R-project.org/
(accessed on 11 March 2019).
29. Fellows, I. Deducer: A data analysis GUI for R. J. Stat. Softw. 2012,49, 1–15. [CrossRef]
30.
Ros, E. Nuts and novel biomarkers of cardiovascular disease. Am. J. Clin. Nutr.
2009
,89, 1649S–1656S.
[CrossRef] [PubMed]
31.
Del Gobbo, L.C.; Falk, M.C.; Feldman, R.; Lewis, K.; Mozaffarian, D. Effects of tree nuts on blood lipids,
apolipoproteins, and blood pressure: Systematic review, meta-analysis, and dose-response of 61 controlled
intervention trials. Am. J. Clin. Nutr. 2015,102, 1347–1356. [CrossRef] [PubMed]
32.
Sabat
é
, J.; Oda, K.; Ros, E. Nut Consumption and Blood Lipid Levels: A Pooled Analysis of 25 Intervention
Trials. Arch. Intern. Med. 2010,170, 821–827. [CrossRef] [PubMed]
33.
US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA National
Nutrient Database for Standard Reference. Current Version: April 2018. Available online: https://ndb.nal.
usda.gov/ndb/search/list (accessed on 25 April 2019).
34. Lue, T. Erectile dysfunction. N. Engl. J. Med. 2000,342, 1802–1813. [CrossRef] [PubMed]
35.
Patel, D.P.; Craig, R.C., Jr.; Myers, J.B.; Brant, W.O.; Hotaling, J.M. Serum Biomarkers of Erectile Dysfunction
in Diabetes Mellitus: A Systematic Review of Current Literature. Sex. Med. Rev.
2017
,5, 339–348. [CrossRef]
[PubMed]
36.
Araña Rosa
í
nz, M.; Ojeda, M.O.; Acosta, J.R.; El
í
as-Calles, L.; Gonz
á
lez, N.; Herrera, O.T.;
Á
lvarez, C.;
Rodr
í
guez, E.; B
á
ez, M.; Seijas, E.; et al. Imbalanced Low-Grade Inflammation and Endothelial Activation in
Patients with Type 2 Diabetes Mellitus and Erectile Dysfunction. J. Sex. Med.
2011
,8, 2017–2030. [CrossRef]
[PubMed]
37.
Gulati, S.; Misra, A.; Pandey, R.M. Effect of Almond Supplementation on Glycemia and Cardiovascular Risk
Factors in Asian Indians in North India with Type 2 Diabetes Mellitus: A 24–Week Study. Metab. Syndr.
Relat. Disord. 2017,15, 98–105. [CrossRef] [PubMed]
38.
Nehra, A.; Jackson, G.; Miner, M.; Billups, K.L.; Burnett, A.L.; Buvat, J.; Carson, C.C.; Cunningham, G.R.;
Ganz, P.; Goldstein, I.; et al. The Princeton III Consensus Recommendations for the Management of Erectile
Dysfunction and Cardiovascular Disease. Mayo Clin. Proc. 2012,87, 766–778. [CrossRef] [PubMed]
39.
Jenkins, D.J.A.; Kendall, C.W.C.; Banach, M.S.; Srichaikul, K.; Vidgen, E.; Mitchell, S.; Parker, T.; Nishi, S.;
Bashyam, B.; De Souza, R.; et al. Nuts as a replacement for carbohydrates in the diabetic diet: A reanalysis of
a randomised controlled trial. Diabetologia 2018,61, 1734–1747. [CrossRef] [PubMed]
40.
Alderson, P. Absence of evidence is not evidence of absence. BMJ
1995
,328, 476–477. [CrossRef] [PubMed]
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2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
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