Gut microbiome, diet linked to fertility in men and women, new guidance says

Health experts say the gut microbiome could play a role in fertility as couples plan to start a family, particularly for those who begin trying later in life. About one in seven couples faces difficulties conceiving, and studies show men's sperm counts have halved over roughly the last 45 years. With the average age of first-time mothers rising to about 31, compared with 22 in previous generations, fertility challenges may be more common than in the past.

Dr. Emily Leeming notes that hormones shape the gut microbiota, and in turn microbes can influence hormone levels. Across genders, the microbiome differs, though differences tend to blur after menopause. Research increasingly explores how vaginal and sperm microbiomes affect reproduction. In the vagina, Lactobacillus helps create a mildly acidic environment that protects against infection; when beneficial microbes decline, infections can rise and potentially impact conception. Bacterial vaginosis, an overgrowth of harmful bacteria, affects about one in three women of reproductive age at some point and, in pregnancy, has been linked to higher risks including preterm birth in roughly one in five infected individuals.

To support fertility, nutrition matters. Both men and women may benefit from reviewing their diets several months before trying to conceive. For women, the three months before ovulation are critical for egg maturation; starting a prenatal supplement with folic acid three months before conception is advised, and choosing one with selenium and vitamins C and E may support egg health by protecting against oxidative stress. Omega-3 fats appear beneficial: a 2024 Heliyon review found higher omega-3 intake associated with higher pregnancy rates. The NHS recommends at least one portion of oily fish per week when trying to conceive, but cautions against exceeding two portions weekly due to potential pollutants; for others, four portions a week is considered safe. For those in their late 30s or early 40s, fertility experts sometimes advise a coenzyme Q10 supplement, an antioxidant that may support egg energy and quality, particularly when eggs are aging. In fertility treatment settings, women who used CoQ10 were about twice as likely to become pregnant compared with those who did not, though researchers note the evidence is still evolving.

Dietary patterns matter as well as single nutrients. A balanced pattern—plenty of fruit and vegetables, whole grains, healthy fats from oily fish, nuts and seeds—helps provide nutrients that support fertility. Key nutrients include omega-3s; observations from a 2024 review suggest that women with higher omega-3 intake were more likely to become pregnant. The guidance on fish intake reflects a careful balance between obtaining omega-3s and limiting exposure to environmental pollutants; many experts advocate modest, regular consumption within the NHS framework.

For men, a balanced diet supports sperm health as well. Zinc, selenium and omega-3 fatty acids—found in shellfish, meat, Brazil nuts and oily fish—are noted as beneficial for sperm count and quality.

Beyond specific nutrients, the science around the microbiome and fertility is still developing. Early studies of probiotics or prebiotics suggest potential in supporting the vaginal microbiome and potentially improving pregnancy outcomes in some cases, especially where a vaginal or womb microbiome is imbalanced. However, results vary by probiotic strain, dose and duration, and some studies show no benefit. A 2024 review in Reproductive Biology and Endocrinology reported mixed findings, underscoring that evidence is not yet conclusive. Anyone considering a probiotic should consult a GP, gynecologist or fertility specialist and choose products that have been evaluated in clinical studies for women’s health rather than general “digestive health” labeling.

Some practical steps can be taken now. In addition to maintaining a diet rich in whole foods, couples are encouraged to focus on a two- to three-month window before trying to conceive, since sperm develop over roughly 74 days and eggs undergo final maturation in the three months before ovulation. Women are advised to begin prenatal supplementation with folic acid before conception and to consider antioxidants such as vitamins C and E and selenium as part of a broader strategy to protect egg health from oxidative stress. For those who drink alcohol, moderation is advised, and tobacco cessation remains important for fertility and overall health.

To satisfy sweet cravings without derailing nutritional goals, a few ideas are offered as a way to support gut health while enjoying treats. Puddings that combine fiber and protein, such as chia puddings made with milk and a touch of honey, can help slow sugar absorption and prolong fullness. Other ideas include dipping fruit in melted dark chocolate or filling Medjool dates with peanut butter and a few dark chocolate chips. Baking peaches or plums with a drizzle of honey and serving with yogurt or ricotta adds fiber, vitamins and healthy fats. The key is to balance desserts with fresh berries and nuts to increase fiber and micronutrient intake.

Ultimately, experts stress that biology is complex and that what couples can control are small, consistent health habits. By focusing on a nutrient-rich diet, screening for vaginal and sperm health when appropriate, and seeking medical guidance when considering supplements or probiotics, couples may improve their chances of conception while supporting overall well-being.