August 09, 2019
Adding nuts to a regular diet significantly improves orgasmic function and sexual desire in healthy young men, according to the FERTINUTS study.
The randomized controlled trial, which was recently published in Nutrients, showed a significant increase in the orgasmic function (P = .037) and sexual desire (P = .040) of men of reproductive age who received the nut intervention in comparison with an age-matched control group.
The researchers found no significant between-group differences in changes during the intervention in erectile function (P = .192), intercourse satisfaction (P = .473), and overall satisfaction (P = .333). In addition, there were no significant correlations between changes in erectile dysfunction parameters and in biochemical parameters during the intervention, write Albert Salas-Huetos, PhD, from University Rovira i Virgili, Reus, Spain, and colleagues.
"None of the possible mechanisms explored (nitric oxide and E-selectin, as surrogate markers of endothelial function) seem to explain the beneficial effects observed on orgasmic function and sexual desire," they write. They add that the 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."
Commenting on the study, Kevin McEleny, FRCS (Urol), consultant urologist from Newcastle upon Tyne NHS Hospitals Foundation Trust, United Kingdom, said, "The study is interesting but not conclusive." He highlighted some marked methodologic flaws: "Self-reported consumption is imperfect in being based on handing back empty packets as proof of consumption, while dietary habits recorded with a diary are subjective."
In addition, he said, the number of participants involved was small, and the authors could not explain why there is a difference in sexual desire and orgasmic function between the groups. "The researchers really needed to look at the psychosexual and hormonal parameters to make a complete comment, but they did not do this," McEleny said.
Erectile dysfunction occurs in only 2% of men younger than 40 years. Prevalence increases markedly with age, to around 52% in men aged 40 to 70 years. Prior studies have shown that nut consumption has beneficial effects on endothelial function, which is implicated in erectile function.
Nuts are nutrient-dense foods that have a relatively high amount of the nonessential amino acid arginine, a precursor of nitric oxide, which is a potent neurotransmitter that plays an important role in erectile action, according to the authors.
Study in Young Men Without Erectile Dysfunction
To better understand the possible role of nut consumption in the primary prevention of erectile dysfunction, the investigators explored the effects of nut supplementation on erectile function and endothelial function by measuring peripheral concentrations of nitric oxide and E-selectin, a marker of endothelial dysfunction.
In the 14-week study, healthy men aged 18 to 35 years were randomly assigned to consume either a usual Western-style diet with an added 60 g/day of a mixture of raw walnuts, almonds, and hazelnuts (nuts group), or a usual Western-style diet in which nuts were avoided (control group). The primary outcome, which was reported previously, showed improved sperm count and quality among men assigned to the intervention group.
In this secondary analysis, Salas-Huetos and colleagues assessed the intervention's effect on self-reported erectile function parameters using the 15-question validated International Index of Erectile Function (IIEF). They also analyzed concentrations of peripheral endothelial biomarkers (nitric oxide and E-selectin) during the study period.
Of the 98 participants who successfully completed the study, 83 (43 in the nuts group and 40 in the control group) completed the IIEF questionnaire and were included in the secondary analysis. Participants were matched for age, and there were no significant differences in baseline parameters between the two groups.
The researchers note that the study findings are consistent with a previous study that reported an increase in all five IIEF domains after consumption of 100 g/day of pistachios for 3 weeks, although that study was conducted in patients who had erectile dysfunction at baseline. "Our study extends the findings to a healthy population without erectile dysfunction supplemented with a mixture of nuts like hazelnuts, almonds, and walnuts," they write.
As a possible explanation for the lack of effect on E-selectin, the researchers note that serum E-selectin appears to be more important with respect to patients with diabetes. "E-selectin ... plays an important role in inflammation," they write. "Because consuming between 60 and 90 g of nuts has proven effective in improving inflammation, it could have been reasonable to detect some differences in this marker due to the nut's supplementation." The lack of effect on E-selectin "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."
The study was designed to assess erectile function with respect to the theory that nuts improve vascular endothelial function, but no difference was found between groups, McEleny noted. He recognized that a difference was found in the orgasm domain and the sexual desire domain of the IIEF. "Looking at the box plot graphs for orgasmic function, there is no box with whiskers for the control group, which automatically means that orgasmic function in the nuts group will be more likely to be significant," he said.
"If you like nuts, then eat them, but I don't think they'll improve your sex life," McEleny concluded.
The authors note that large studies are warranted to confirm these results and to elucidate possible mechanisms for these benefits.
The study work was partially supported by the International Nut and Dried Fruit Council, a nonprofit organization registered with the Register of Foundations of Catalonia, Spain; and by Human Nutrition Unit. The authors and McEleny have disclosed no relevant financial relationships.