Can mercury in fish affect your period and fertility?

What's actually in it

Seafood is the main dietary source of methylmercury, a toxic metal that accumulates up the food chain. Larger predatory fish like tuna, swordfish, shark, and king mackerel have the highest levels. Mercury is a known neurotoxin, but it also affects the endocrine system and may interfere with reproductive hormones.

For women trying to conceive, mercury exposure is especially concerning because it can disrupt the menstrual cycle and the hormonal signals needed for ovulation and implantation.

What the research says

A 2025 study in J Nutr measured mercury levels in hair samples of women seeking fertility care and compared them to menstrual symptoms and omega-3 fatty acid status. Hair mercury reflects long-term dietary exposure from seafood.

Women with higher hair mercury levels reported more menstrual symptoms. The association held even after accounting for omega-3 levels, which tend to be higher in women who eat more fish. The findings suggest the mercury is causing harm that the beneficial omega-3s can't fully offset.

The study highlights a real dilemma: fish is good for you (omega-3s are linked to better fertility outcomes), but the mercury that comes with it may be doing harm at the same time.

Choose low-mercury fish like salmon, sardines, anchovies, and trout to get the omega-3 benefits with less mercury risk. Limit high-mercury species like tuna and swordfish to once a week or less, especially if you're trying to conceive.