Take-home messages:

​Introduction

While not all women or couples aspire to have children, for many, becoming parents fulfils significant social and gender-identity roles. However, achieving pregnancy is often more challenging than many anticipate. Educating oneself about fertility and adopting healthier behaviours can substantially increase the chances of conceiving and ensure better pregnancy outcomes.

While aligning family planning with the biological clock is ideal, pursuing education and career goals often means that age becomes a significant factor in fertility. The biological clock impacts fertility differently across genders; men typically experience a gradual decline in fertility starting around age 40, while women face a sharper decline after age 35 (1-4). However, various lifestyle choices can still play a crucial role in enhancing fertility despite age-related challenges. Among the crucial lifestyle choices for optimal health—such as avoiding smoking (5) and engaging in balanced regular physical activity (6) and effectively managing stress (7) (see Table 1 below)—the role of nutrition is particularly significant. Proper nutrition not only affects mate selection, attractiveness and sexual arousal but also enhances fertility in both sexes, increasing the chances of conception. A balanced diet, rich in fruits, vegetables, protein sources and high-quality dietary fats, is essential, particularly during the periconceptional period. This critical time around conception involves weeks before and after pregnancy onset and is vital for ensuring sufficient intake of essential micronutrients and maintaining an optimal body weight. Both nutritional adequacy and a healthy body mass index are linked to improved fertility. Adequate nutrition is also linked to a reduced risk of preeclampsia, a pregnancy complication characterised by high blood pressure and signs of damage to another organ system. By prioritising nutrition, individuals can lay a solid foundation for a successful path to parenthood, significantly enhancing their reproductive health.

Table 1: Impact of Demographic, Lifestyle Factors and Stress on Fertility in Men and Women

IVF, In Vitro Fertilisation; PCOS, Polycystic Ovary Syndrome

Nutritional Influences on Mate Selection and Attraction Dynamics

Research indicates a distinct preference among women for men who are tall and have broad shoulders (13). This preference suggests that physical attributes such as height and upper body strength, which are often associated with good nutrition and health throughout life, play a significant role in attractiveness. Conversely, chronic undernutrition can lead to stunting, affecting height attainment and subsequently reducing the likelihood of being chosen as a mate.

Similarly, men's preferences for women tend to focus on indicators that suggest health and fertility, such as body mass index (BMI), body fat percentage (BF%) and waist-to-hip ratio (WHR). These preferences underline the importance of potential female mates displaying signs of good health and fertility (14, 15). Indicators of female fertility, including smooth skin, plump lips, well-defined muscles, a healthy BMI range of 18.5–24.9 kg/m² and a WHR close to 0.70, are critical (16). Both BMI and WHR are significant in assessing adiposity, affecting the female body's appearance and influencing perceptions of physical attractiveness.

Studies in rodents and humans show that higher levels of inflammation make individuals appear less attractive, as evidenced by male rodents' disinterest in inflamed females and human participants looking less appealing after inflammatory injections (17-19). Obesity is known to increase inflammation in the body, which may explain why a healthy body weight is generally more desirable across various populations, as it is associated with lower inflammation and potentially greater attractiveness. Additionally, what we eat can either increase inflammation (inflammatory diets) or reduce it (anti-inflammatory diets), affecting our overall health and attractiveness. This connection between nutrition and physical attributes underscores the role of nutritional status in mate selection even before any sexual interaction occurs.

Nutritional Influences on Sexual Arousal

Dietary choices, particularly vegan diets, may have a favourable impact on sexual health, including nighttime erections (also known as nocturnal penile tumescence) and reducing erectile dysfunction a common issue linked with aging indicating early cardiometabolic disease (20, 21). While direct studies are limited, the cardiovascular benefits associated with a plant-based diet—such as improved blood flow and nitric oxide production—support the notion that vegan diets could enhance erectile function. Although direct studies are scarce, the cardiovascular advantages of a plant-based diet, such as enhanced blood flow and increased nitric oxide production, suggest that vegan diets could improve erectile function. However, it is advisable to moderate soy intake within these diets. Soy contains isoflavones like genistein, daidzein and glycitein, which are structurally like oestrogen and can bind to oestrogen receptors, potentially acting as weak oestrogens or anti-oestrogens and being associated with erectile dysfunction. Animal studies have demonstrated that large amounts of daidzein can induce structural changes in the penile tissue, such as increased collagen and reduced smooth muscle and elastic fibres, which might impair erectile function (22, 23). Additionally, a case report highlighted an 18-year-old who developed erectile dysfunction linked to low testosterone levels due to a high soy vegan diet, which was reversible upon discontinuing the soy-rich diet (24).

The relationship between diet and arousal in women, is a growing area of interest. Research on the impact of diet on female sexual health, including libido, arousal and satisfaction, is less extensive than on male erectile function. The Mediterranean diet, which focuses on whole grains, fresh fruits and vegetables, fish and polyunsaturated fats, has been shown to lower inflammation markers in women, regardless of whether they are of healthy weight (25, 26) or overweight (27). It has also been associated with improved sexual function, especially in sexual desire and arousal (27-29), in women with metabolic syndrome. Additionally, an energy-restricted diet, known to decrease chronic inflammation (30), has been found to enhance sexual desire and arousal in overweight women (31). Research on soy's impact on women's sexual function is sparse but promising (8, 32). However, a case study on persistent sexual arousal syndrome showed that excessive soy intake worsened symptoms and should be avoided (Amsterdam et al., 2005).

Impact of Micronutrients on Fertility

Numerous studies have examined the relationship between fertility and various micronutrients—including antioxidants, B-vitamins and minerals—as well as amino acid derivatives, polyunsaturated fatty acids, and carbohydrates (33-36). IHere I highlight key findings concerning these micronutrients and other nutritional factors, including their impact on weight status.

Carnitines, derived from an amino acid, are naturally present in meat, poultry, fish and milk, and can also be synthesised in the liver and kidneys from lysine derivatives. Vegetarians tend to have lower levels of carnitines compared to omnivores (37). Carnitines are water-soluble antioxidants (35). L-carnitine is a bioactive carnitine. L-carnitine and L-acetyl-carnitine are particularly noted for their importance in male reproductive health (38, 39), leading researchers to use these supplements in treating male infertility characterised by sperm dysfunction (40). Zhou and colleagues evaluated the effectiveness of these supplements through a review of experimental studies, finding that L-carnitine and L-acetyl-carnitine enhanced pregnancy rates, sperm motility, and reduced abnormal sperm cells, although they had no effect on sperm concentration or semen volume. While dietary intake and natural body synthesis generally satisfy carnitine needs, certain conditions such as genetic disorders, chronic renal failure, or specific antibiotic use can impair carnitine absorption and increase its excretion, thereby necessitating supplementation (41).

Vitamin C, vitamin E, folate, selenium, zinc, carnitines, co-enzyme Q10 and lycopene are antioxidants that effectively scavenge free radicals, neutralise their effects and prevent the chain reactions that lead to oxidative stress in body tissues. These antioxidants are particularly beneficial in reversing oxidative stress-induced sperm dysfunction and enhancing pregnancy rates (35). Although these antioxidants are often used alone or in combination, the optimal regimen has yet to be determined. It is crucial to maintain balance, as excessive consumption of antioxidants may result in reductive stress, which could be harmful (35). Supplementation with selenium (alone or combined with N-acetylcysteine), polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), co-enzyme Q10 and a combination of zinc and folic acid, as well as L-carnitine and acetyl-L-carnitine, appears to improve the spermiogram in infertile men (33). A summary of  randomised control trials investigating the efficacy of oral nutritional agents including some of the antioxidants among women with polycystic ovary syndrome (PCOS), a hormonal abnormality (36) revealed that inositol (a type of sugar/carbohydrate) supplementation have advantages in increasing sex hormone binding globulin and improving glycolipid metabolism when compared with co-enzyme Q10, vitamin E and vitamin D. However, vitamin E in particular may be a better in reducing total testosterone and increasing sex hormone binding globulin in women.

Zinc, a mineral found abundantly in meat, poultry, shellfish, legumes, seeds, nuts, dairy and eggs, is among the most extensively researched nutrients concerning fertility (42). Zinc has unique properties that make it essential in men’s fertility. Its crucial role in male fertility is well-documented, acting as a hormone balancer and an antibacterial agent within the male urea system. It is vital for maintaining the integrity of epithelial tissues (maintaining the lining of the reproductive organs) and may have a regulative role in the progress of capacitation and acrosome reaction (an exocytotic event that allows cells to penetrate the zona pellucida and fuse with the oocyte plasma membrane to achieve successful fertilisation) (43, 44). As an antioxidant, zinc particularly benefits infertile male smokers by mitigating the adverse effects of toxins and heavy metals (44). Zinc deficiency can significantly impair spermatogenesis, lead to sperm abnormalities and adversely affect testosterone levels (42, 44). The zinc-to-copper ratio, is important with higher levels of copper in men experiencing infertility, underscoring the need to manage this balance (42). Addressing zinc deficiency is crucial, particularly in men, to enhance fertility prospects for couples aiming to conceive.

Vitamin D plays a critical role in reproductive processes in both sexes, with its receptors and metabolising enzymes present in reproductive tissues of women and men (45). In mice, the absence of vitamin D receptors leads to gonadal insufficiency, reduced sperm count and motility, and abnormalities in reproductive organs (as reviewed by Lerchbaum and Obermayer-Pietsch (45). Vitamin D is involved women’s reproduction including in vitro fertilisation (IVF) outcome (clinical pregnancy rates) and PCOS, might influence steroidogenesis of sex hormones (oestradiol and progesterone) and high circulating vitamin D levels might be associated with endometriosis. Low vitamin D levels in women with PCOS are associated with obesity and metabolic issues, and supplementation is advised to improve menstrual regularity and metabolic function. In men, adequate vitamin D levels are linked to better semen quality and higher testosterone levels (45). Given its importance for reproductive and overall health, adequate (not too much) sun exposure and consuming foods rich in vitamin D, such as oily fish, red meat, liver and egg yolks, are recommended.

Impact of Macronutrients on Fertility

Energy from macronutrients, along with micronutrients, impacts fertility, with chronic energy consumption influencing body weight and central obesity, as indicated by body mass index (BMI) and waist circumference. Maintaining a healthy weight supports fertility, though it does not ensure conception. Being underweight (BMI under 18.5) can disrupt hormone balance, affecting ovulation and the chance of getting pregnant (46) and also slightly increase the risk for miscarriage (47).

Overweight and obesity are linked to reproductive failures (48), including infertility-related conditions like PCOS (49, 50). They also contribute to insulin resistance, characterised by hyperinsulinaemia, hyperandrogenaemia (increased peripheral aromatisation of androgens to oestrogens), altered hormone secretion and disruptions in the regulation of the hypothalamic-pituitary-gonadal axis, all of which can negatively affect (49) Furthermore, overweight and obesity are linked to more pregnancy-related complications (high blood pressure (preeclampsia), diabetes) (51), higher preterm and miscarriage rate (52, 53) and greater likelihood of birth defects in children born to obese mothers (BMI of 30 or greater)(54). In men, obesity is associated with lower testosterone (55), poorer sperm quality (56) and a higher rate of erectile dysfunction (57).

Impact of Alcohol and Caffeine on fertility

Research indicates that consuming alcoholic beverages may reduce fertility in both women and men, although the specific mechanisms in women remain unclear (58) In men, alcohol consumption is linked to reduced semen volume and adverse effects on sperm morphology (59). Additionally, while studies suggest that caffeine alone does not significantly impact fertility (60, 61) it may exacerbate the detrimental effects of alcohol on the likelihood of conception. Moreover, caffeine intake during pregnancy is associated with an increased risk of spontaneous abortion (61).

Dietary supplements and Fertility

Exercise caution with fertility supplements, as a systematic review found that most male fertility supplements available in the US lack solid evidence to support their effectiveness (62). Similarly, dietary supplements for erectile dysfunction show inconsistent efficacy, with only a few showing promise based on the effectiveness and dosing of ingredients; however, they generally do not have enough evidence to be recommended as primary treatment options (63).

Diet and Pregnancy Outcomes

Table 2: Association between diet and pregnancy outcomes and complications

(64)

Conclusion

In conclusion, the profound influence of diet on both fertility and pregnancy outcomes underscores the necessity for a balanced and nutrient-rich dietary approach. For couples considering parenthood, it is crucial to adopt a lifestyle that supports reproductive health by maintaining a healthy body weight, following a nutrient-dense diet and minimising alcohol consumption. These lifestyle choices significantly boost the likelihood of conception and ensure optimal pregnancy outcomes, thereby enhancing overall well-being. By embracing such a comprehensive nutritional strategy, individuals not only pave the way for successful conception but also contribute to the broader spectrum of a healthy lifestyle. This holistic approach not only bolsters reproductive health but also enhances the general vitality and well-being of prospective parents.

Reflections

Diet Audit: Spend a week tracking your daily food intake to assess how well your diet aligns with fertility-enhancing nutritional guidelines. Focus on the inclusion of fruits, vegetables, lean proteins and whole grains, and reduction of alcoholic beverages reproductive health.

Nutrition and Mate Selection Connection: With a partner or on your own, reflect on how your nutritional choices might influence perceptions of attractiveness and mate selection, based on the research linking nutrition with physical characteristics and fertility signals such as skin health, body composition and overall vitality.

Plant-Based Diet Challenge: Try a plant-based diet for a month, focusing on increasing your intake of fruits, vegetables, nuts, seeds and whole grains. Reflect weekly on how this diet impacts your energy levels, physical health and sexual health, including aspects like libido and performance, which are indicators of overall reproductive health.

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In the process of creating this work, the author employed ChatGPT 4 to streamline the text and to perform language editing.