Meat, Poultry, Fish, Tofu: Which Protein is Best and Which is Worst for Your Fertility?

Why protein matters for fertility

Protein is a core part of a well-rounded diet -- your body needs it for growth, maintenance, energy, and it's a building block of bones, muscles, skin, enzymes, and hormones. Feeding rats a protein-restricted diet results in impaired embryo implantation and far fewer offspring, so protein matters for your future baby too. But does the type of protein matter? Chicken or fish, pork or beef, soy or turkey, beans or yogurt? A lot of research has focused on dairy specifically (covered in its own piece), so let's start with meat.

Beef? Pork? Chicken? Fish?

Less than 10% of people in the US are vegetarian, so most people get the bulk of their protein from meat. Researchers from Harvard used the Nurses' Health Study -- thousands of women surveyed on diet every 2 years for 8 years, including whether they'd struggled to conceive or had ovulation issues -- to look at meat consumption and fertility. Women in the top 20% of total protein intake (meat, fish, dairy, beans) had a much higher risk of ovulatory infertility. Each additional daily serving of meat (holding calories constant) was linked to a 32% greater risk. The worst offenders: red meat (beef, pork, lamb, venison) at 42% higher risk, and poultry (chicken, turkey) at 53% higher. Processed meat and fish didn't move the needle much.

Looking deeper: evidence from IVF

Nothing in science is settled until it replicates. A more recent study tested whether women undergoing IVF had lower antral follicle counts (a proxy for ovarian reserve) tied to meat consumption, and found no link -- reassuring on that specific front. But there's more to fertility than ovulating and having enough eggs; egg and embryo quality matter too. Researchers from Brazil tested embryo quality (specifically, whether embryos reached the blastocyst stage by day 5) against maternal meat consumption, and found blastocyst rates were lowest in women eating a lot of red meat, neutral for mostly-chicken eaters, and highest for women who regularly ate fish. Red meat came out as the consistent problem across both ovulation and embryo quality.

Vegetable protein

Beans, lentils, cereal, cheese, pasta, soy, tofu -- there's fairly convincing evidence that this kind of protein can actually help. One driver of infertility is Premature Ovarian Failure/Insufficiency (early menopause), and Nurses' Health Study data found women in the top 20% of vegetable protein intake had a 16% lower risk of early menopause than low consumers, with each additional 1% of daily vegetable protein lowering the risk by 6%. Soy, tofu, and -- somewhat surprisingly -- pasta had the biggest impact; an additional daily serving of pasta was linked to a 36% lower risk of early menopause. Pasta isn't a high-protein food on its own (5-8g per 100g serving), so the likelier explanation is that heavy pasta-eaters also tend to follow a broader Mediterranean-style dietary pattern, which is independently linked to better fertility.

Soy and tofu

Soy contains isoflavones, compounds that mimic estrogen (a "phytoestrogen") and can bind to estrogen receptors, influencing the reproductive system. A 2019 Brazilian study gave female mice soy isoflavones for 8 weeks and found they protected eggs and possibly extended ovarian lifespan; another found embryo quality improved with a soy-enriched diet. But it's not universally positive: a study of thousands of women from the Adventist church (known for encouraging healthy, often vegetarian lifestyles) found very high soy isoflavone intake (50mg/day) in women over 40 linked to a slightly lower (4%) chance of having children. Reaching 50mg/day takes real effort -- average Western intake is under 3mg, and tofu contains about 22mg per 100g, so you'd need to be a genuine tofu enthusiast to get there.

So is soy good or bad?

The clearest winners appear to be couples already struggling to conceive. A 2015 Harvard study of 315 women undergoing IVF found higher soy consumption linked to a higher chance of pregnancy and a healthy delivery, and another IVF study found high-dose soy isoflavones improved pregnancy rates to 30.3% versus 16.2% on placebo. Two proposed mechanisms: improving endometrial thickness (found in women undergoing IUI), and counteracting the negative effects of BPA, a man-made phytoestrogen found in many plastics that's known to hurt fertility -- soy's natural isoflavones seem to displace or block it. So if you're struggling to conceive, soy could genuinely help, especially with high BPA exposure.

The bottom line

• Eating less meat can improve ovulation problems
• Meat consumption isn't linked to fewer eggs, but egg and embryo quality can improve by eating less of it (especially beef, pork, venison)
• More vegetable protein, especially replacing meat, is linked to better fertility and cycle regularity, particularly as you get older
• More vegetable protein could delay the onset of menopause
• More vegetable protein can help if you're struggling with infertility
• Tofu and soy contain isoflavones that may help fertility

If you're having trouble conceiving, swapping meat for beans, lentils, or tofu a few nights a week is a low-risk, reasonably well-supported change.

References

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