Fatty acids, food groups and semen variables in men referring to an Italian Fertility Clinic: Cross-sectional analysis of a prospective cohort study

Assessing the influence of preconception diet on male fertility: a systematic scoping review

BACKGROUND

The last decade has seen increased research on the relationship between diet and male fertility, but there are no clearly defined nutritional recommendations for men in the preconception period to support clinical fertility outcomes.

OBJECTIVE AND RATIONALE

The purpose of this scoping review is to examine the extent and range of research undertaken to evaluate the effect(s) of diet in the preconception period on male clinical fertility and reproductive outcomes.

SEARCH METHODS

Four electronic databases (MEDLINE and EMBASE via Ovid, CAB Direct, and CINAHL via EBSCO) were searched from inception to July 2023 for randomized controlled trials (RCTs) and observational studies (prospective/retrospective, case-control, and cross-sectional). Intervention studies in male participants or couples aiming to achieve dietary or nutritional change, or non-intervention studies examining dietary or nutritional components (whole diets, dietary patterns, food groups or individual foods) in the preconception period were included. Controls were defined as any comparison group for RCTs, and any/no comparison for observational studies. Primary outcomes of interest included the effect(s) of male preconception diet on clinical outcomes such as conception (natural or via ART), pregnancy rates and live birth rates. Secondary outcomes included time to conception and sperm parameters.

OUTCOMES

A total of 37 studies were eligible, including one RCT and 36 observational studies (prospective, cross-sectional, and case-control studies; four studies in non-ART populations) published between 2008 and 2023. Eight reported clinical outcomes, 26 reported on secondary outcomes, and three reported on both. The RCT did not assess clinical outcomes but found that tomato juice may benefit sperm motility. In observational studies, some evidence suggested that increasing fish or reducing sugar-sweetened beverages, processed meat or total fat may improve fecundability. Evidence for other clinical outcomes, such as pregnancy rates or live birth rates, showed no relationship with cereals, soy and dairy, and inconsistent relationships with consuming red meat or a 'healthy diet' pattern. For improved sperm parameters, limited evidence supported increasing fish, fats/fatty acids, carbohydrates and dairy, and reducing processed meat, while the evidence for fruits, vegetables, cereals, legumes, eggs, red meat and protein was inconsistent. Healthy diet patterns in general were shown to improve sperm health.

WIDER IMPLICATIONS

Specific dietary recommendations for improving male fertility are precluded by the lack of reporting on clinical pregnancy outcomes, heterogeneity of the available literature and the paucity of RCTs to determine causation or to rule out reverse causation. There may be some benefit from increasing fish, adopting a healthy dietary pattern, and reducing consumption of sugar-sweetened beverages and processed meat, but it is unclear whether these benefits extend beyond sperm parameters to improve clinical fertility. More studies exploring whole diets rather than singular foods or nutritional components in the context of male fertility are encouraged, particularly by means of RCTs where feasible. Further assessment of core fertility outcomes is warranted and requires careful planning in high-quality prospective studies and RCTs. These studies can lay the groundwork for targeted dietary guidelines and enhance the prospects of successful fertility outcomes for men in the preconception period. Systematic search of preconception diet suggests that increasing fish and reducing sugary drinks, processed meats and total fat may improve male fertility, while consuming healthy diets, fish, fats/fatty acids, carbohydrates and dairy and reducing processed meat can improve sperm health.

Ultra-processed food consumption and semen quality parameters in the Led-Fertyl study

STUDY QUESTION

Is ultra-processed food (UPF) consumption associated with semen quality parameters?

SUMMARY ANSWER

Higher UPF consumption was inversely associated with total sperm count, sperm concentration, and total motility in men of reproductive age.

WHAT IS KNOWN ALREADY

The consumption of UPF, which has been rising during the last decades, has been demonstrated to be positively associated with several chronic diseases such as diabetes or cardiovascular diseases. However, the scientific evidence on its potential impact on semen quality remains notably limited.

STUDY DESIGN SIZE DURATION

A cross-sectional analysis was conducted using data from 200 healthy men (mean age 28.4 ± 5.5 years) enrolled in the Led-Fertyl (Lifestyle and Environmental Determinants of Seminogram and Other Male Fertility-Related Parameters) study between February 2021 and April 2023.

PARTICIPANTS/MATERIALS SETTING METHODS

UPF consumption (% of energy from UPF) was estimated according to the NOVA classification system using a validated 143-item semi-quantitative food frequency questionnaire. Total sperm count, sperm concentration, sperm vitality, total motility, progressive motility, and normal sperm forms were set as the main outcomes. Microscopic parameters were analyzed using a phase-contrast microscope and a computer-assisted sperm analysis (CASA) system. Semen samples were collected and tested according to World Health Organization 2010 standards. Multivariable linear regression models were fitted to estimate the associations between UPF tertile and semen quality parameters.

MAIN RESULTS AND THE ROLE OF CHANCE

Sperm concentration (β: -1.42 × 106 spz./ml; 95% CI: -2.72 to -0.12) and motility (β: -7.83%; 95% CI: -15.16 to -0.51) were lower in participants in the highest tertile of UPF compared to the lowest. A similar association was observed for sperm count when UPF was analyzed per 10% increment of energy from UPF consumption (β: -1.50 × 106 spz.; 95% CI: -2.83 to -0.17). Theoretically replacing 10% of energy from UPF consumption with 10% of energy from unprocessed or minimally processed food consumption was associated with a higher total sperm count, sperm concentration, total motility, progressive motility, and normal sperm forms.

LIMITATIONS REASONS FOR CAUTION

Cross-sectional studies do not permit the drawing of causal inferences. Measurement errors and reporting bias cannot be entirely ruled out.

WIDER IMPLICATIONS OF THE FINDINGS

This work suggests that consumption of UPF may have an impact on certain semen quality parameters. Furthermore, opting for unprocessed or minimally processed foods instead of UPFs could potentially benefit semen quality. If these results are replicated in future epidemiological studies with different long-term designs, these novel findings could provide valuable insights for updating or even designing preventive and interventional programs to address infertility among men of reproductive age.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the Spanish government's official funding agency for biomedical research, ISCIII, through the Fondo de Investigación para la Salud (FIS), the European Union ERDF/ESF, 'A way to make Europe'/'Investing in your future' [PI21/01447], and the Diputació de Tarragona (2021/11-No.Exp. 8004330008-2021-0022642). J.S.-S. gratefully acknowledges the financial support of ICREA under the ICREA Academia program. C.V.-H. received a predoctoral grant from the Generalitat de Catalunya (2022 FI_B100108). M.Á.M. was supported by the Sara Borrell postdoctoral fellowship (CD21/00045-Instituto de Salud Carlos III (ISCIII)). M.F.d.l.P. was supported by a predoctoral grant from the Rovira i Virgili University and Diputació de Tarragona (2020-PMF-PIPF-8). All authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Role of Mediterranean diet in endocrine diseases: a joint overview by the endocrinologist and the nutritionist

PURPOSE

The purpose of this review is to examine the current evidence on the potential role of Mediterranean diet (MD) in the prevention and management of endocrine disorders and to highlight the importance of interdisciplinary collaboration between endocrinologists and nutritionists.

METHODS

A literature search was conducted using PubMed and Google Scholar databases to identify relevant studies published in English. Studies were selected based on their relevance to the role of MD in the prevention and management of endocrine disorders. The search terms included "Mediterranean diet," "endocrine disorders," "thyroid disorders," "gonadal disorders," and "neuroendocrine tumors".

RESULTS

The studies reviewed suggest that MD may have a beneficial effect in the prevention and management of various endocrine disorders, including thyroid disorders, gonadal disorders, and neuroendocrine tumors. MD has been associated with decreased risk of nodular thyroid disease and thyroid cancer, improved male and female reproductive health, and a potential role in the management of neuroendocrine tumors. MD's anti-inflammatory and antioxidant properties, as well as its high levels of phytochemicals, may play a role in its beneficial effects.

CONCLUSION

Interdisciplinary collaboration between endocrinologists and nutritionists is essential for the optimal management of endocrine disorders, including the potential role of MD in their prevention and management. While further research is needed, the current evidence suggests that MD may have a protective effect against endocrine disorders, and its incorporation into dietary recommendations may be beneficial.

Diet and recreational drug use in relation to male reproductive health

Diet and lifestyle interventions present promising avenues for the improvement of male fertility. Our objective was to review and synthesize the existing observational and experimental studies among humans on the associations of diet and recreational drug use with semen quality and fertility outcomes. The available data on this topic are limited and, at times, conflicting. Nevertheless, on the basis of this review, dietary patterns that are composed of higher intakes of fruits, vegetables, whole grains, nuts, low-fat dairy, and seafood, as well as lower intakes of red and processed meats, sweets, and sugar-sweetened beverages were identified as having the strongest evidence for associations with better sperm quality. However, whether these dietary patterns translate into positive associations with clinical fertility endpoints such as assisted reproductive technology success rates or time-to-pregnancy among couples trying to conceive without medical assistance remains unclear. Male caffeine and alcohol intake, within low-to-moderate ranges of intake, do not appear to be detrimental to semen quality. Yet high-quality research on this topic, focused on clinical fertility endpoints, should continue given the conflicting evidence, particularly in populations undergoing infertility treatment with assisted reproductive technology. Recreational drug use, including marijuana, electronic cigarettes, and other illicit drugs, does not appear to be beneficial for male reproductive health and should be avoided or ceased. In conclusion, men should be encouraged to consume a healthy diet rich in fruits, vegetables, whole grains, nuts, low-fat dairy, and seafood, as well as lacking in red and processed meats, sweets, and sugar-sweetened beverages, and to avoid recreational drug use for improved male reproductive health.

Association of male fatty acid intake with fecundability among couples planning pregnancy

STUDY QUESTION

To what extent is male fatty acid intake associated with fecundability among couples planning pregnancy?

SUMMARY ANSWER

We observed weak positive associations of male dietary intakes of total and saturated fatty acids with fecundability; no other fatty acid subtypes were appreciably associated with fecundability.

WHAT IS KNOWN ALREADY

Male fatty acid intake has been associated with semen quality in previous studies. However, little is known about the extent to which male fatty acid intake is associated with fecundability among couples attempting spontaneous conception.

STUDY DESIGN, SIZE, DURATION

We conducted an internet-based preconception prospective cohort study of 697 couples who enrolled during 2015-2022. During 12 cycles of observation, 53 couples (7.6%) were lost to follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were residents of the USA or Canada, aged 21-45 years, and not using fertility treatment at enrollment. At baseline, male participants completed a food frequency questionnaire from which we estimated intakes of total fat and fatty acid subtypes. We ascertained time to pregnancy using questionnaires completed every 8 weeks by female participants until conception or up to 12 months. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% CIs for the associations of fat intakes with fecundability, adjusting for male and female partner characteristics. We used the multivariate nutrient density method to account for energy intake, allowing for interpretation of results as fat intake replacing carbohydrate intake. We conducted several sensitivity analyses to assess the potential for confounding, selection bias, and reverse causation.

MAIN RESULTS AND THE ROLE OF CHANCE

Among 697 couples, we observed 465 pregnancies during 2970 menstrual cycles of follow-up. The cumulative incidence of pregnancy during 12 cycles of follow-up after accounting for censoring was 76%. Intakes of total and saturated fatty acids were weakly, positively associated with fecundability. Fully adjusted FRs for quartiles of total fat intake were 1.32 (95% CI 1.01-1.71), 1.16 (95% CI 0.88-1.51), and 1.43 (95% CI 1.09-1.88) for the second, third, and fourth vs the first quartile, respectively. Fully adjusted FRs for saturated fatty acid intake were 1.21 (95% CI 0.94-1.55), 1.16 (95% CI 0.89-1.51), and 1.23 (95% CI 0.94-1.62) for the second, third, and fourth vs the first quartile, respectively. Intakes of monounsaturated, polyunsaturated, trans-, omega-3, and omega-6 fatty acids were not strongly associated with fecundability. Results were similar after adjustment for the female partner's intakes of trans- and omega-3 fats.

LIMITATIONS, REASONS FOR CAUTION

Dietary intakes estimated from the food frequency questionnaire may be subject to non-differential misclassification, which is expected to bias results toward the null in the extreme categories when exposures are modeled as quartiles. There may be residual confounding by unmeasured dietary, lifestyle, or environmental factors. Sample size was limited, especially in subgroup analyses.

WIDER IMPLICATIONS OF THE FINDINGS

Our results do not support a strong causal effect of male fatty acid intakes on fecundability among couples attempting to conceive spontaneously. The weak positive associations we observed between male dietary fat intakes and fecundability may reflect a combination of causal associations, measurement error, chance, and residual confounding.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the National Institutes of Health, grant numbers R01HD086742 and R01HD105863. In the last 3 years, PRESTO has received in-kind donations from Swiss Precision Diagnostics (home pregnancy tests) and Kindara.com (fertility app). L.A.W. is a consultant for AbbVie, Inc. M.L.E. is an advisor to Sandstone, Ro, Underdog, Dadi, Hannah, Doveras, and VSeat. The other authors have no competing interests to report.

TRIAL REGISTRATION NUMBER

N/A.

Fatty acids intake and outcomes of assisted reproduction in women referring to an Italian Fertility Service: cross sectional analysis of a prospective cohort study

BackgroundInfertility involves 15% of couples in Italy and approximately 10-12% worldwide.Focusing on female fertility, it can underline multiple causes, among them the diet has a great influence. Methods We investigated whether the consumption of some fatty acids affects four outcomes of the assisted reproduction techniques. From September 2014 to December 2016, women referring to our Italian fertility unit, eligible for assisted reproduction techniques, were invited to participate. Information on dietwere recorded through a validated food frequency questionnaire. Results494 women were included, of whom95% achieved good quality oocytes, 87% resulted in embryo transfer, 32.0%in clinical pregnancies, and 24.5% in pregnancy at term.The fourth quartile of saturated fatty acids consumption, compared to the first one, showed an association with clinical pregnancy (adjusted relative risk 0.67, 95% confidence interval 0.45 to 1.00, p=0.0491). Some associations emerge accounting for confounders. Age was associated with clinical pregnancy and pregnancy at term in the models considering all fatty intakes and food groups variables but was not associated with oocytes quality and embryo transfer. Physical activity was associated with clinical pregnancy. ConclusionsThere is biologic plausibility of the effect of omega-3 and omega-6 polyunsaturated fatty acids on oocyte development via eicosanoids synthesis, even if our results showed limited associations.Future research is aimed to measure serum levels of fatty acids and investigate the assisted reproduction techniques' outcomes. This article is protected by copyright. All rights reserved.

Preconception diet, fertility, and later health in pregnancy

PURPOSE OF REVIEW

Women should enter pregnancy in the best possible health. There is increasing recognition of the importance of nutrition for reproductive health; however, key dietary factors in relation to optimizing fertility are nonexistent. The purpose of this review is to investigate dietary factors, preconception, and the association with fertility and later health in pregnancy.

RECENT FINDINGS

This article summarizes recent literature assessing preconception dietary intake and the association with fertility, time to pregnancy, and also the relationship with polycystic ovary syndrome and gestational diabetes; these conditions associate with each other, and also with infertility. The impact of paternal diet is also reported.

SUMMARY

There is recent interest investigating diet and time to pregnancy, suggesting higher intakes of fruit, minimal intake of fast food and sugar sweetened beverages, and a diet lower in glycemic load, may improve time to pregnancy. There is minimal recent literature on paternal diet and impact on fertility. Present advice to women with polycystic ovary syndrome is in line with international recommendations for lifestyle management to improve reproductive outcomes; and for gestational diabetes, prepregnancy may be an optimal time to improve dietary intakes, particularly through consumption of an overall healthy dietary pattern or a Mediterranean-style dietary pattern.