One of the most cited studies in this field is the 'Fertility Diet', described by Chavarro and colleagues using data from the Nurses' Health Study II. The researchers followed more than 17,000 women and found that those who followed certain dietary patterns less often reported difficulty conceiving due to anovulatory infertility.
The pattern included: more plant protein and less animal protein (especially red meat), wholegrains instead of rapidly absorbed carbohydrates, healthy fats — primarily olive oil and nuts, adequate iron from plant sources, and full-fat dairy rather than low-fat (a curious and counter-intuitive finding).
This pattern overlaps substantially with the Mediterranean diet — one of the most researched dietary models in the world. Several studies link adherence to Mediterranean eating with better IVF outcomes, though results are not uniform.
Folic acid (vitamin B9) is the only micronutrient whose supplementation before pregnancy is a justified clinical recommendation in all developed countries. A deficiency in the very early weeks of pregnancy substantially raises the risk of neural tube defects in the foetus — in the first 28 days, when many women don't yet know they're pregnant.
The standard recommendation: 400 to 800 micrograms of folic acid per day, starting one to three months before planned conception. Some women — those with an MTHFR polymorphism, obesity, diabetes or a history of gastrointestinal surgery — may need higher doses or methylfolate instead of the standard form.
Food sources: dark leafy greens (spinach, broccoli), legumes, liver. But reaching the required level through food alone is difficult — hence the supplement recommendation.
Vitamin D has attracted considerable attention in fertility research. Its receptors are found in the ovaries, uterus and testes. Vitamin D deficiency is associated with reduced ovarian reserve, menstrual cycle irregularities and poorer IVF outcomes. But causation hasn't been established: it's not clear whether deficiency causes the problems or whether it reflects them.
That said, vitamin D is inexpensive, safe at reasonable doses and widely deficient in northern latitudes — particularly in people who spend little time outdoors. Most fertility specialists recommend checking levels and correcting a deficiency before starting treatment.
Trans fatty acids — hydrogenated vegetable fats historically used in margarine, industrial baked goods and fast food — are linked with elevated risk of anovulatory infertility. The evidence is convincing enough to avoid them.
Omega-3 fatty acids (oily fish, flaxseed oil, walnuts) are the opposite story. Evidence on omega-3 and male fertility is relatively solid: regular fish consumption is associated with better semen parameters. For female fertility the data are less clear-cut, but these fats matter for foetal brain development regardless.
Olive oil — the cornerstone of Mediterranean eating — is associated with better reproductive outcomes, though drawing a clean causal line is difficult.
Oxidative stress — cellular damage caused by free radicals — is one of the mechanisms through which egg and sperm quality declines with age. Antioxidants should theoretically counteract this process.
Coenzyme Q10 (CoQ10) has attracted the most attention in the fertility context. Small studies in women with reduced ovarian reserve showed improvements in egg quality when taking 400 to 600 mg of CoQ10 daily for several months before stimulation. The findings are intriguing, but the evidence base is weak — no large randomised controlled trials exist.
Vitamins C and E, zinc, selenium — part of antioxidant therapy for male factor infertility. Some meta-analyses show modest improvements in semen parameters. The impact on live birth rates is considerably less clear.
The main takeaway: antioxidants from food — colourful vegetables and fruit, leafy greens, nuts — are unambiguously beneficial and carry no risk. High-dose isolated antioxidants in supplement form are moderately interesting but unproven.
If there's one lifestyle factor that genuinely affects fertility, body weight is probably the most powerful. And it goes in both directions.
Excess weight disrupts hormonal balance. Adipose tissue is a source of oestrogens, and when there's too much of it, excess oestrogen suppresses ovulation. In men, overweight reduces testosterone levels and worsens semen parameters. In PCOS, a weight loss of just 5 to 10% frequently restores ovulatory cycles without any other intervention.
Underweight is equally problematic. Significant caloric restriction — or intense athletic training without adequate nutrition — suppresses the hypothalamic-pituitary-ovarian axis. Periods disappear. Ovulation disappears. This is a physiological protective mechanism: the body conserves resources and 'decides' that now is not the time for pregnancy.
Superfoods and 'fertility foods'. Pomegranate, avocado, pineapple — all healthy foods, but there's no evidence that they specifically influence conception. Marketing in this space is ahead of the science by roughly decades.
Radical diets and detoxes. Fasting and extreme cleanses don't improve fertility — they suppress it. Particularly ill-advised when planning a pregnancy.
'Organic' as a panacea. No evidence that organic produce improves fertility compared with conventional food when other factors are equal.
Diet affects fertility — but not as dramatically as Google promises. The realistic version: a varied diet with plenty of vegetables, fruit, wholegrains, legumes, healthy fats and moderate protein; folic acid as a supplement before conception; a healthy body weight; no trans fats. Unglamorous — but that's what works.
If you're undergoing fertility treatment, diet is an important but supporting factor. It doesn't replace clinical intervention. But good nutrition creates a better physiological context for whatever treatment you're having.
Anovulatory infertility — difficulty conceiving caused by absent or irregular ovulation. The form of female infertility most responsive to lifestyle changes.
CoQ10 (Coenzyme Q10) — an antioxidant involved in cellular energy metabolism. Being studied as a way to improve egg quality in reduced ovarian reserve.
Mediterranean diet — a dietary pattern based on vegetables, fruit, wholegrains, legumes, fish and olive oil with minimal red meat and sugar. One of the most studied healthy eating models.
MTHFR — a gene encoding an enzyme involved in folate metabolism. Certain variants (polymorphisms) reduce the efficiency of folic acid processing; methylfolate is preferred in those cases.
Oxidative stress — damage to cellular structures caused by free radicals. One of the mechanisms behind age-related decline in gamete quality.
Trans fatty acids (trans fats) — a type of fatty acid formed during vegetable oil hydrogenation. Found in industrially produced baked goods, margarine and some fast food. Associated with elevated risk of anovulatory infertility and cardiovascular disease.
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