In a recent systematic review published within the journal Advances in Nutrition, researchers investigated the associations between nut consumption and fertility outcomes in human adults. Literature from 4 online scientific databases was collated and subjected to a meta-analysis. Following the full-text screening, 4 publications comprising 875 participants were included. Study findings revealed that consuming ≥ 60g nuts/day had profound useful effects on male fertility via increased sperm vitality and motility and improved sperm morphology in comparison with controls. While studies on the impacts of nuts on female fertility remain scarce, this study emphasizes that as little as two servings of nuts per day can significantly improve sperm parameters directly related to fertility in men.
Review: Nut consumption and fertility: a scientific review and meta-analysis. Image Credit: Marie Sonmez Photography / Shutterstock
The growing issue of infertility
Infertility is a severe condition characterised by the lack to conceive despite 12 months of unprotected and regular sexual activity. Infertility has been observed to negatively affect couples’ social, financial, and psychological health, and its prevalence has been linked to parental age, nutrition, clinical health, and genetic hormonal disorders.
Infertility is a worldwide concern, estimated to affect between 8-12% of all reproductive-age adults (18-49 years). Alarmingly, incidences of infertility are on the rise, especially in underdeveloped and developing countries, where one in every 4 couples experience difficulties in conceiving. In some areas, infertility rates are reported to satisfy or exceed 30%.
Despite substantial research into the causes and mechanisms of the condition, between 10-15% of infertility don’t have any diagnosable underpinning. The first intervention in these cases is the usage of assisted reproductive technologies (ART). Nevertheless, these interventions present a considerable financial burden, with an ordinary in vitro fertilization (IFV) cycle costing upwards of US$19,200.
“Considerable economic, racial, ethnic, geographic and cultural disparities in access to fertility treatments also exist, thus research aiming at maximising natural fertility is of utmost importance.”
Recent research has focused on identifying modifiable aspects, including food regimen and health behaviors, that may improve fertility outcomes. The Mediterranean food regimen (MedDiet), characterised by high fish, fruit, and vegetable intake, stays the very best studied, with findings suggesting that MedDiet adherence increases the number of obtainable embryos and improves fertilization rate in previously subfertile women. In men, the food regimen has been related to enhanced sperm concentrations and motility and increased sperm count.
Constructing upon the MedDiet, Gaksins et al. developed the Pro-Fertility food regimen, characterised by high concentrations of vitamins B12 and D and folic acid, aimed toward maximizing female fertility and optimal fetal development. On condition that pesticide use has been related to lowered fertility and adversarial fetal outcomes, the Pro-Fertility food regimen further prescribes low exposure to foods derived from pesticide-supplemented crops.
“While the studies that aim to determine a relationship between dietary patterns and fertility outcomes can provide insightful information, they might also represent a challenge to those that have very distinct dietary habits. Thus, identifying the advantages of particular foods can elucidate dietary strategies which are easier to be implemented.”
Nuts present a great potential solution for people adhering to the Western food regimen and similar suboptimal dietary intakes. Nuts depict high concentrations of proteins, fibers, minerals, vitamins, and bioactive compounds with assumed advantages in fertility. Their ratios of Omega-3:Omega-6 fatty acids and low saturated fat concentrations have been found to suppress quite a few chronic diseases related to cardiovascular and mental health.
In regards to the study
The current study goals to research the associations between nut intake and positive fertility outcomes. It comprises a scientific review and meta-analysis and adheres to the referred Reporting Items for Systematic Reviews and Meta-Analyses (The PRISMA Statement) guidelines.
Data collection comprised searching 4 online databases, MEDLINE, Scopus, Embase, and CINAHL, from the inception till 30 June 2023 for all literature on food regimen (specifically nut consumption) and fertility. Inclusion criteria comprised any cross-sectional, cohort, case-control, or randomized clinical trial (RCT) that included human subjects of reproductive age (18-49) for a minimum duration of three months. The three-month period was enforced because regular sperm maturation cycles take 76 days to finish.
The Covidence Systematic Review Software was used for initial screening (title and abstract) and subsequent data extraction. The Cochrane Risk of Bias 2 and the Risk Of Bias In Non-randomized Studies–of Interventions (ROBINS-I) tools were used to evaluate included publications for methodology and consequence bias.
Statistical analyses comprised a random mixed effects model meta-analyses that evaluated the standardized mean difference (SDM) between case and control outcomes for every included study. The Cochrane Q statistic and I2 metrics were used to measure inter-study heterogeneity.
An initial database search identified 11,691 publications for title and abstract screening, of which 57 papers were retained. Full-text screening further discarded 53 papers, leading to a final review dataset of 4 publications comprising 646 men and 229 women participants. All studies were included within the systematic review. Two studies were found to have top quality and low heterogeneity and were thus included within the meta-analysis.
Each included meta-analysis studies followed RCT methodologies and focused on the outcomes of nut consumption in men in tandem with a Western-style food regimen. Interventions included 60 – 75g of nuts or nut supplements provided each day for 12 weeks. Analyses revealed that cases (nut-supplemented males) were found to indicate significantly improved sperm parameters (motility, vitality, and morphology) in comparison with their control counterparts (no nuts in food regimen) following just 60g/day of nut consumption.
“In contrast, two non-randomised studies involving participants with varied fertility status found no convincing evidence for the association between dietary nut consumption of ≤ 1 serve per day and markers of sperm quality (men) or rates of embryo implantation, clinical pregnancy or live birth following ART (men and women).”
Interestingly, the Western-style food regimen is taken into account unhealthy and has been related to severe mental and physical health conditions, including depression, heart problems, and cancers. Previous literature has correlated high Western food regimen adherence to declining male reproductive success. The finding that nut intake can’t only reverse the demerits of the Western food regimen but in addition improve sperm parameters above the mean of the MedDiet highlights the importance of nut food regimen supplementation as a secure, natural, and cheap intervention against infertility.
Unfortunately, evidence for the useful impacts of nuts on female fertility is proscribed. Future research should investigate this association, and if findings are positive, recommend nuts to healthcare practitioners and prospective parents as a key behavioral modification in improved fertility outcomes.