The inclusion of nuts in a regular diet significantly improves the quality and function of human sperm, according to results of a randomised trial which measured conventional semen parameters and molecular changes over a 14-week study period. The findings, say the investigators, "support a beneficial role for chronic nut consumption in sperm quality" and reflect a research need for further male-specific dietary recommendations.
The results of the study are presented today by Dr Albert Salas-Huetos from the human nutrition unit of the Universitat Rovira i Virgil in Reus, Spain.
The study was performed, he said, against a background of general decline in quantity and quality of human sperm, attributed in industrialised countries to "pollution, smoking, and trends toward a western-style diet".
In this study subjects randomised to the nut group had significant improvements in their sperm count, vitality, motility and morphology (shape); these were consistent with improvements found in other recent studies with diets rich in omega-3, antioxidants (vitamin C and E, selenium and zinc), and folate. Nuts are dense foods containing many of these nutrients and other phytochemicals.
The study was a 14-week randomised clinical trial in which 119 healthy young men aged 18-35 were allocated to either their usual western-style diet supplemented with 60 grams/day of mixed almonds, hazelnuts and walnuts, or their usual western-style diet without nuts. In its analysis the study recorded not just sperm parameters (according to World Health Organisation benchmarks) but also changes in several molecular factors, including sperm DNA fragmentation. Sperm and blood samples were analysed at baseline and after 14 weeks of intervention.
Results firstly found significantly higher levels of sperm count, vitality, motility and morphology in the men randomised to the 60 g/day nut diet than in those following their usual diets free of nuts. Improvements in the former group were by around 16% in sperm count, 4% in sperm vitality, 6% in sperm motility, and 1% in morphology. These four parameters, explained Salas-Huetos, are all associated with male fertility. Moreover, the subjects in the nut group also showed a significant reduction in their levels of sperm DNA fragmentation, a parameter closely associated with male infertility. Indeed, it was this change in the level of DNA fragmentation in the sperm cells by which the investigators explained, at least in part, the improvement in sperm count, motility and morphology.
Although these are statistically significant results from a randomised trail with a high level of scientific evidence, Salas-Huetos emphasised that subjects in the study were all healthy and apparently fertile men following a western-style diet. He thus warned that results cannot be extrapolated to the general population.
So, should men hoping to conceive a baby – either naturally or with IVF – add nuts to their everyday diet? "We can't yet say that," said Salas-Huetos, "based solely on the results of this study. But evidence is accumulating in the literature that healthy lifestyle changes such as following a healthy dietary pattern might help conception – and of course, nuts are a key component of a Mediterranean healthy diet."
Abstract
Study question: Can a chronic consumption of a mixture of nuts improve the semen quality parameters and the sperm functionality in healthy individuals?
Summary answer: Including nuts in a regular diet significantly improved the sperm count, vitality, motility, and morphology, partly explained by a reduction of the DNA fragmentation.
What is known already: Human semen quality has declined in industrialized nations where pollution, smoking, and trends toward a western-style diet are hypothesized as potential causes. Recently, some studies described that healthy diets rich in omega-3, antioxidants (vitamin C and E, selenium and zinc), carnitines and folate could improve semen quality. Because nuts are nutrient dense foods containing some of the above-mentioned nutrients, we hypothesize that, added to a western-style diet, would beneficially affect semen quality and functionality.
Study design, size, duration: The study was designed as a 14-week randomized, controlled, parallel two-group trial. 119 healthy male aged 18-35 were allocated to either following their usual western-style diet supplemented with 60 g/day of a mix of almonds, hazelnuts and walnuts or to follow with their usual western-style diet free of nuts. Participants/materials, setting, methods: Sperm and blood samples were collected at baseline and after 14 weeks of intervention. Dietary information was recorded in four visits distributed along the trial. Conventional semen parameters (WHO, 2010) were determined as primary outcome. To elucidate at the molecular level the effects of nuts consumption, sperm DNA fragmentation (TUNEL assay), sperm ROS (chemiluminescence using Luminol), sperm chromosome stability (FISH for chromosomes X, Y and 18) and total sperm DNA methylation (ELISA assay) were measured. Main results and the role of chance: A total of 98 participants completed the study. General characteristics of the study population (age, weight, height, BMI, waist circumference, and systolic and diastolic blood pressure) did not differ between interventions. No significant differences were observed in conventional blood biochemical parameters (fasting plasma glucose, total cholesterol, HDL, LDL and VLDL cholesterol, triglycerides, fasting plasma insulin, C-reactive protein and folate). In nuts group, we found a significant increased intake of total lipids, MUFA, PUFA, magnesium, vitamin E, omega-3, ALA, and omega-6. We found an improvement of sperm count (P-value=0.0043), vitality (P-value=0.0027), total motility (P-value=0.0093), progressive motility (Pvalue=0.0207), and morphology (P-value=0.0073) in the nut group compared to the control. Participants in the nuts group shown a significant reduction of the sperm DNA fragmentation (SDF) (P-value=0.0018) a parameter closely related with male infertility. Negative correlations between sperm vitality and SDF (rho=-0.2252; P-value=0.0266), and between total spermatozoa and SDF (rho=-0.3170; P-value=0.0015) were detected. No changes between interventions were found in ROS (P-value=0.1996), sperm chromosome (X, Y and 18) anomalies (P-value disomies=0.3336, P-value nullisomies=0.9386, and Pvalue diploidies=0.0674), and DNA methylation (P-value=0.8652).
Limitations, reasons for caution: By design, a limitation of this trial is that it focuses on health, apparently fertile and with western-style diet subjects, and the results cannot be extrapolated to the general population.
Wider implications of the findings: Our findings support a beneficial role of chronic nut consumption in sperm quality and explore the molecular mechanism that could explain our results. Additional efforts to identify male-specific dietary recommendations that optimize sperm quality and fertility should be encouraged.
Authors
A Salas-Huetos, R Moraleda, S Giardina, E Anton, J Blanco, J Salas-Salvadó, M Bulló
[link url="https://www.eshre.eu/ESHRE2018/Media/ESHRE-2018-Press-releases/Salas.aspx"]European Society of Human Reproduction material[/link]
ESHRE 2018 abstract O-238 (PDF)