No single food will make you infertile overnight, but several dietary patterns can measurably reduce your chances of conceiving over time. The biggest culprits are trans fats, sugary drinks, highly processed meats, and diets heavy in refined carbohydrates. These foods affect fertility through overlapping mechanisms: they disrupt hormone balance, impair ovulation, reduce sperm quality, and increase inflammation throughout the body.
Trans Fats and Ovulatory Infertility
Trans fats are the single most damaging type of fat for fertility. Research from Harvard Medical School found that women who got just 2% of their daily calories from trans fats (about 4 grams on an 1,800-calorie diet) had a 73% greater chance of developing ovulatory infertility compared to women who ate those calories as carbohydrates instead. When compared to women eating healthy monounsaturated fats like olive oil, trans fat consumption carried more than double the risk. And each additional 4 grams of trans fat per day raised the risk by another 73%.
Trans fats show up in partially hydrogenated oils, some fried foods, certain packaged baked goods, and shelf-stable snack foods. While many countries have restricted their use, they still appear in smaller amounts across the food supply. Checking ingredient labels for “partially hydrogenated oil” is the most reliable way to spot them.
Sugary Drinks Lower Monthly Conception Odds
Women who drank one or more sugar-sweetened sodas per day had a 26% lower probability of conceiving in any given menstrual cycle compared to women who avoided them entirely. This finding comes from a large North American preconception study that tracked couples actively trying to get pregnant. The effect held even after researchers adjusted for body weight, age, and other lifestyle factors, which suggests the sugar itself plays a role beyond simply contributing to weight gain.
The likely mechanism is insulin. Large, rapid spikes in blood sugar force the body to produce more insulin, and chronically elevated insulin interferes with the hormonal signals that trigger ovulation. This is one reason sugary drinks are more problematic than the same amount of sugar eaten in solid food: liquids cause faster, sharper blood sugar spikes.
Refined Carbohydrates and Blood Sugar
The sugar problem extends well beyond soda. Diets high in rapidly digested carbohydrates, like white bread, white rice, pastries, and sugary cereals, affect fertility through the same insulin pathway. A case-control study found that women with high-glycemic diets had roughly 3.7 times the odds of infertility compared to women with the lowest glycemic load. Both the type and quantity of carbohydrates mattered: eating large amounts of fast-digesting carbs was worse than eating moderate amounts of slower-digesting ones.
This connection is especially strong for women with polycystic ovary syndrome (PCOS), one of the most common causes of ovulatory infertility. Insulin resistance is a core feature of PCOS, and high-glycemic diets make it worse. But the association between blood sugar swings and impaired ovulation appears in women without PCOS too.
Processed Meat and Sperm Quality
For men, processed meats like bacon, sausage, hot dogs, and deli meats are the dietary category most consistently linked to poorer fertility. A study of men attending a fertility clinic found that those who ate the most processed red meat had 23.2% fewer normally shaped sperm than men who ate the least. Sperm shape (morphology) matters because abnormally formed sperm have a harder time reaching and fertilizing an egg.
Interestingly, total meat intake was not associated with worse sperm quality. Unprocessed red meat and poultry showed no negative relationship with sperm count, motility, or morphology. The problem appears to be specific to processing: the nitrates, preservatives, and other additives in cured and processed meats seem to be the issue rather than animal protein itself. Fish intake, by contrast, was favorably associated with better semen quality in the same study.
Pesticide Residues on Produce
Fruits and vegetables are generally good for fertility, but the pesticides on them can work against you. A study of 325 women undergoing IVF treatment found that those who ate the most high-pesticide produce (2.3 or more servings per day of items like strawberries, spinach, and peppers) had an 18% lower chance of clinical pregnancy and a 26% lower chance of live birth compared to women who ate the least. The probability of pregnancy loss also climbed steadily with higher pesticide exposure, rising from 7% in the lowest intake group to 34% in the highest.
The practical takeaway is not to avoid produce. Swapping just one daily serving of high-pesticide fruits and vegetables for a low-pesticide alternative was associated with 88% higher odds of live birth. The Environmental Working Group publishes an annual list ranking produce by pesticide levels. Buying organic versions of the highest-residue items, or choosing naturally low-pesticide options like avocados, onions, and sweet corn, can reduce exposure without sacrificing nutrition.
Low-Fat Dairy May Backfire
This one surprises most people. Data from the Nurses’ Health Study, one of the largest long-running studies of women’s health, found that one to two daily servings of full-fat dairy (whole milk, full-fat yogurt, or regular cottage cheese) appeared to protect against ovulatory infertility, while skim and low-fat dairy products had the opposite effect. The likely explanation involves fat-soluble hormones: when fat is removed from milk, the balance of hormones it contains shifts in ways that may interfere with ovulation.
If you’re actively trying to conceive, temporarily switching from skim to whole milk is a simple change that may improve your odds. This doesn’t mean unlimited ice cream. It means choosing full-fat versions of the dairy you already eat.
Alcohol During Key Cycle Phases
Alcohol’s effect on fertility depends on how much you drink and when in your cycle you drink it. Heavy drinking (more than six drinks per week) during the luteal phase, the roughly two-week window between ovulation and your next period, cut the odds of conception nearly in half. Even moderate drinking (three to six drinks per week) during the luteal phase reduced fecundability by 44%. Heavy drinking around ovulation itself was even more damaging, lowering conception odds by 61% compared to non-drinkers.
These effects likely stem from alcohol disrupting the precise hormonal sequence needed for a fertilized egg to implant in the uterine lining. The luteal phase and ovulatory window are the most hormonally sensitive parts of the cycle, which explains why timing matters so much.
Caffeine Has a Threshold
Moderate coffee drinking appears to be fine for fertility. The concern starts above 300 milligrams of caffeine per day, which is roughly three 8-ounce cups of brewed coffee. Nonsmoking women who exceeded that threshold had a fecundability ratio of 0.74, meaning their monthly chance of conceiving was about 26% lower than women who drank less. They were also 2.65 times more likely to experience delayed conception lasting over a year. Women who stayed at or below 300 milligrams daily showed no increased risk.
Soy Is Probably Fine
Despite persistent rumors, soy does not appear to harm fertility in either men or women at normal dietary levels. A comprehensive review found that soy isoflavones, the plant compounds that weakly mimic estrogen, have no clinically relevant effect on menstrual cycle length, key reproductive hormones like estradiol and progesterone, or overall fertility outcomes in healthy women. For men, two separate meta-analyses confirmed that soy intake does not affect sperm quality or reproductive hormone levels. Some early research even suggests soy may have a modest benefit for women with PCOS, though that evidence is still limited.
The fear around soy came from animal studies using doses far higher than what any human would eat. At the amounts found in tofu, edamame, soy milk, and tempeh, the evidence consistently points toward safety.