A new study published in Human Reproduction found that higher intake of ultraprocessed foods around the time of conception was associated with reduced fertility in men and subtle changes in early embryonic growth, suggesting that what you eat before trying to conceive matters more than previously thought.

How Does Diet Before Conception Affect Fertility?

The period surrounding conception is critical for fertility and early development. Researchers from the Generation R Next Study, a population-based prospective cohort study, examined how ultraprocessed food (UPF) consumption in the months before conception influenced both the ability to get pregnant and how embryos develop in the earliest weeks .

The study included 831 women and 651 male partners who were attempting conception or already pregnant. Participants completed a food frequency questionnaire at a median of 12 weeks of gestation to capture their eating habits around the time of conception. Ultraprocessed foods were identified using the NOVA classification system, which categorizes industrially manufactured products high in sugar, salt, unhealthy fats, and additives .

The findings revealed a striking sex-specific pattern. In men, higher UPF intake was linked to a 10% decrease in fecundability, which is the probability of conceiving within one month, per standard deviation increase in UPF consumption. Men with higher ultraprocessed food intake also showed increased subfertility risk, meaning they were more likely to take longer than 12 months to conceive or require assisted reproductive technology .

What Specific Changes Occur in Early Embryonic Development?

Beyond fertility, maternal ultraprocessed food consumption showed associations with early embryonic growth. Researchers measured crown-rump length (CRL), which is the distance from the top of the fetal head to the buttocks, and yolk sac volume at 7, 9, and 11 weeks of gestation using transvaginal ultrasound .

The crown-rump length was reduced at 7 weeks of gestation across the full range of increasing maternal UPF intake. Yolk sac volume was also smaller at seven weeks in women with the highest UPF consumption compared to those with the lowest intake. The yolk sac is particularly important because it nourishes the embryo until the placenta takes over, and poor yolk sac growth may increase the risk of miscarriage and preterm birth .

These associations persisted even after researchers adjusted for lifestyle, social, and demographic factors, including body mass index (BMI), education level, ethnicity, age, folic acid supplementation, and substance use. Notably, the associations were observed at relatively low levels of UPF intake, suggesting that even moderate consumption may have effects .

How to Optimize Your Diet Before Conception

• Reduce Ultraprocessed Foods: Limit consumption of nutrient-poor, industrially manufactured products high in sugar, salt, unhealthy fats, and additives. In some wealthy countries, UPFs can contribute up to 60% of daily energy intake, so awareness of what you're eating is crucial .
• Focus on Whole Foods: Emphasize whole grains, legumes (dals), vegetables, and other nutrient-dense foods. Indian diets traditionally provide good nutrition through these staple foods, which should form the foundation of your periconceptional diet .
• Maintain a Healthy Weight: Aim for a BMI between 18.5 and 24.9 kg/m2, which translates to roughly 110 to 165 pounds for someone 5'6" tall. Both partners should prioritize weight management as part of fertility preparation .
• Take Prenatal Vitamins: Begin prenatal vitamins before conception to ensure adequate nutrient intake, particularly folic acid, which supports early embryonic development .
• Limit Caffeine and Prioritize Sleep: Cut down on caffeine consumption and ensure you're getting enough sleep, as both partners' overall health supports fertility .

The research suggests that certain subgroups of ultraprocessed foods may be particularly problematic. Artificially sweetened drinks and processed meats show consistent links to multiple adverse health outcomes, while processed breads and cereals do not show the same associations. However, breads constituted a major portion of UPF intake in this study, which may explain why some ultraprocessed categories showed weaker effects .

Why Does Paternal Diet Matter for Fertility?

One of the most striking findings is that paternal ultraprocessed food consumption had a more pronounced effect on fertility than maternal consumption. While women showed no association between UPF intake and fecundability, men with higher UPF intake experienced reduced fertility outcomes .

The researchers propose several mechanisms for why ultraprocessed foods may impair male fertility. Many UPFs have poor nutritional profiles that can trigger oxidative stress, elevated testosterone levels, and potential mitochondrial dysfunction, all of which may impair sperm motility. Additionally, UPF packaging often contains endocrine disruptors such as phthalates, which may directly affect male fertility .

The median UPF intake was 22% of total food intake in women versus 25% in men, suggesting that men typically consume more ultraprocessed foods. Interestingly, correlation within couples was low, with 57% of couples reporting discordant consumption patterns, meaning partners often have very different diets .

What Does This Mean for Your Fertility Timeline?

If you're planning to pursue fertility treatment, understanding the full timeline can help you prepare. The fertility treatment journey typically begins with initial consultation and testing in the first month. During this phase, women undergo blood tests to check hormone levels like AMH (anti-mullerian hormone), FSH (follicle-stimulating hormone), and thyroid function, plus an ultrasound to evaluate the ovaries and uterus. Men provide a semen analysis, which is critical since male factors cause nearly 40 to 50% of infertility cases .

Once testing is complete, your doctor may suggest timed intercourse, ovulation medicines, intrauterine insemination (IUI), or in vitro fertilization (IVF) based on the results. IUI typically happens within one menstrual cycle, while IVF takes 6 to 8 weeks for one complete cycle, including stimulation, retrieval, and transfer. On average, women complete 2 to 3 IVF cycles before achieving pregnancy, so the entire journey from first consultation through successful conception may take 6 to 12 months .

Starting dietary improvements now, before you begin any fertility treatment, positions you to optimize both your natural fertility and your response to assisted reproductive technologies. The research suggests that the months leading up to conception are a critical window for dietary intervention, making this an ideal time to reduce ultraprocessed foods and focus on whole, nutrient-dense options .

The findings underscore the need for both partners to examine their eating habits when planning to conceive. While the study was conducted in a healthy population and cannot establish direct causality, the results suggest that personalized dietary guidance for both men and women could become an important part of fertility counseling and prenatal care .