Fertility Diet: Evidence-Based Nutrition for Conception

The most comprehensive research on diet and fertility comes from the Nurses' Health Study II, which identified that a dietary pattern characterised by higher intake of plant protein (particularly from legumes), full-fat dairy, low-glycaemic carbohydrates, non-haem iron from plants, and multivitamins was associated with a 66 per cent lower risk of ovulatory infertility compared to the typical Western diet.

The Mediterranean diet has similarly strong evidence for fertility. A 2018 study published in Human Reproduction found that women who closely followed a Mediterranean diet in the six months before IVF treatment had a 65–68 per cent higher likelihood of achieving a clinical pregnancy and live birth compared to those with the lowest adherence. The Mediterranean pattern — rich in vegetables, legumes, whole grains, fish, olive oil, and nuts, with limited red meat and processed foods — reduces inflammation, improves insulin sensitivity, and provides the antioxidants that protect reproductive cells from oxidative damage.

A pro-fertility dietary framework emphasises: adequate plant protein from legumes, nuts, seeds, and tofu; oily fish for omega-3 DHA and EPA; full-fat dairy (over low-fat); low-GI carbohydrates over refined carbohydrates; abundant colourful vegetables; and minimising ultra-processed foods, refined sugars, and trans fats. Trans fats — found in commercially fried foods, some margarines, and many processed snacks — have particularly strong evidence for impairing fertility; a 2% increase in energy from trans fats was associated with a doubling of ovulatory infertility risk in the Nurses' Health Study.

Folate is the most well-established preconception nutrient. Adequate folate from diet and supplementation (400 micrograms of folic acid daily) is essential from before conception — not only to prevent neural tube defects but also to support DNA methylation and early embryo development. Some women have the MTHFR gene variant that impairs folate conversion; these women may benefit from the methylated form (methylfolate) rather than standard folic acid.

Coenzyme Q10 (CoQ10) has attracted significant research interest for egg quality. Mitochondrial function is critical to egg maturation and early embryo development, and CoQ10 — a key mitochondrial antioxidant — declines with age. Several small trials have shown that CoQ10 supplementation (200–600mg daily) improves egg quantity and quality in women with poor ovarian reserve, particularly those over 35. Dietary sources include oily fish, organ meats, and whole grains, but food amounts are lower than therapeutic doses.

Iron from plant foods has a specific positive association with fertility beyond its general health effects. The Nurses' Health Study found that women with the highest non-haem iron intake (from plants and supplements rather than haem iron from meat) had the lowest rates of ovulatory infertility. Lentils, beans, tofu, spinach, and fortified cereals paired with vitamin C provide meaningful non-haem iron.

Vitamin D affects ovarian follicle development, uterine receptivity, and implantation. Multiple studies link vitamin D deficiency with lower IVF success rates. Have your vitamin D level checked and supplement to maintain levels above 50 nmol/L. Omega-3 fatty acids from oily fish and algae supplements support follicle development, egg maturation, uterine blood flow, and implantation by modulating prostaglandins and reducing inflammation in the reproductive tract.

Male factor infertility contributes to roughly half of all cases where a couple struggles to conceive, yet male nutrition receives far less attention. Sperm quality — including count, motility, and morphology — is significantly influenced by diet, oxidative stress, and nutritional status.

Oxidative stress is one of the most important modifiable factors affecting sperm quality. Reactive oxygen species damage sperm DNA, impair motility, and reduce fertilisation capacity. A diet rich in antioxidants — vitamin C (bell peppers, citrus, kiwi), vitamin E (nuts, seeds, olive oil), selenium (Brazil nuts, fish, eggs), zinc (oysters, pumpkin seeds, beef), lycopene (cooked tomatoes, watermelon), and beta-carotene (orange and yellow vegetables) — helps neutralise oxidative damage.

Omega-3 fatty acids are essential components of sperm cell membranes and influence sperm motility and morphology. Men with poor sperm parameters frequently have low omega-3 status. A 2020 study in Human Reproduction Update found that omega-3 supplementation significantly improved sperm concentration and motility. Two to three portions of oily fish per week, or an omega-3 supplement providing at least 1g of combined EPA/DHA daily, is advisable.

Zinc is particularly important — it is highly concentrated in seminal fluid and supports sperm production, motility, and testosterone metabolism. Brazil nuts provide selenium, with just two to three nuts providing the full recommended daily amount. Folate and vitamin B12 also support sperm DNA integrity.

Diet quality on the whole matters more than individual nutrients. The Western dietary pattern — high in red and processed meat, full-fat dairy, refined carbohydrates, and convenience foods — is consistently associated with poorer sperm parameters across large population studies. Conversely, the Mediterranean pattern is associated with higher sperm quality, including better motility, morphology, and DNA integrity.

Body weight sits at both ends of the fertility spectrum. Both underweight and overweight are associated with impaired fertility, though through different mechanisms.

Excess body fat, particularly visceral fat, raises oestrogen levels (fat tissue converts androgens to oestrogen via aromatase), disrupts LH and FSH pulsatility needed for ovulation, increases insulin resistance, and can cause anovulatory cycles. Even modest weight loss of five per cent of body weight in women with obesity has been shown in multiple trials to restore ovulatory cycles, improve IVF outcomes, and increase natural conception rates.

Underweight status, or severe dietary restriction, suppresses the reproductive axis through hypothalamic amenorrhoea — the body essentially shuts down reproduction when energy availability is too low. Women with a BMI below approximately 18.5, those with a history of restrictive eating or excessive exercise, and athletes with low energy availability may lose menstrual function and ovulation. Restoring adequate caloric intake and body weight typically restores menstrual regularity, though this may take several months.

Insulin resistance — whether related to PCOS, excess weight, or dietary patterns high in refined carbohydrates — disrupts the fine hormonal balance needed for regular ovulation. Low-glycaemic dietary approaches that prioritise complex carbohydrates, protein, and fibre while minimising refined sugars improve insulin sensitivity and ovulatory function. The DASH diet and Mediterranean diet both improve insulin sensitivity and have evidence for improving fertility outcomes.

For couples undergoing IVF, maintaining a healthy weight is associated with significantly better outcomes — higher retrieval rates, better embryo quality, higher implantation rates, and reduced miscarriage risk. Even small weight changes in the months before a cycle can be meaningful.

Couples undergoing IVF receive a lot of conflicting advice about diet during stimulation and transfer cycles. The evidence base is growing but some principles are well-established.

During ovarian stimulation, the ovaries are working intensively to mature multiple follicles. Adequate protein intake supports follicular fluid production and cellular repair. Omega-3-rich foods support follicle development and reduce the systemic inflammation that can impair implantation. Antioxidant-rich foods (berries, colourful vegetables, green tea in moderation, nuts) reduce oxidative stress in the follicular environment.

After egg retrieval, risk of ovarian hyperstimulation syndrome (OHSS) is a concern for some women. A high-protein diet in the days following retrieval helps maintain oncotic pressure, reduce fluid shifts, and support recovery. Some fertility clinics recommend increasing protein to 100–120g per day post-retrieval.

In the implantation window around embryo transfer, several foods have traditional or emerging evidence: brazil nuts for selenium, pomegranate juice for its potential role in uterine blood flow, pineapple (core included, for bromelain) — though the evidence for the latter two is largely anecdotal and mechanistic rather than from robust clinical trials. More reliably, ensuring adequate vitamin D, continuing a Mediterranean eating pattern, avoiding alcohol, and managing stress through the transfer period is evidence-backed.

Some substances are worth specifically avoiding during IVF: high-dose vitamin A supplements (retinol form) should be avoided as excess retinol is teratogenic; high caffeine intake should be reduced; alcohol should ideally be eliminated; and extreme dietary restriction should be avoided as it impairs hormonal support for implantation.