Several vitamins and nutrients have strong evidence behind them for supporting fertility in both women and men. Folic acid, vitamin D, and CoQ10 top the list for women, while zinc, selenium, and carnitine show measurable improvements in sperm quality for men. The specifics matter, though, so here’s what the research actually shows for each one.
Folic Acid: The Non-Negotiable Starting Point
The CDC recommends that all women capable of becoming pregnant take 400 mcg of folic acid every day. This is primarily to prevent neural tube defects in early pregnancy, but the timing is critical: you need to start at least one month before conception, since the neural tube forms in the first weeks, often before you know you’re pregnant. Continue taking it through pregnancy.
Folic acid is the synthetic form of folate, a B vitamin found naturally in leafy greens, beans, and fortified grains. Most prenatal vitamins contain the recommended 400 mcg, making this the simplest box to check on your fertility supplement list.
Vitamin D and Pregnancy Rates
Vitamin D plays a bigger role in conception than most people realize. In a study of women undergoing fertility treatment, those with adequate vitamin D levels (above 50 nmol/L, or roughly 20 ng/mL) had a clinical pregnancy rate of 42.2%, compared to 30.6% in women who were deficient. Higher vitamin D was an independent predictor of pregnancy, increasing the odds by about 46% per unit increase in the predictive model.
Vitamin D deficiency is extremely common, especially in northern climates and among people who spend most of their time indoors. A simple blood test can check your levels. Food sources include fatty fish, egg yolks, and fortified milk, but most people need a supplement to reach adequate levels.
CoQ10 for Egg Quality After 35
Coenzyme Q10 is a molecule your cells use to produce energy. Eggs are among the most energy-demanding cells in the body, and as women age, the energy-producing structures inside eggs (mitochondria) become less efficient. This is one of the core reasons fertility declines with age.
Research in animal models has shown that CoQ10 supplementation restores energy production in aging eggs to levels comparable to younger ones. It also corrected the structural problems that cause chromosomal errors during cell division, which are a major source of miscarriage and failed implantation in women over 35. Supplementing with CoQ10 essentially helped aging eggs behave more like young ones in terms of energy output and chromosome organization.
Many fertility specialists recommend CoQ10 for women over 35, particularly in the form called ubiquinol, which is more easily absorbed. Optimal dosing hasn’t been established in large-scale human trials yet, but it’s widely used in clinical fertility practice.
Omega-3 Fatty Acids and Egg Maturation
DHA, the omega-3 fatty acid found in fish oil, has a striking effect on egg quality. In one study, 44% of eggs from animals on a DHA-rich diet were fully mature and ready for fertilization, compared to just 13% on a standard diet. Only 12% of eggs from the DHA group were degenerating, versus 39% in the control group.
The benefits went deeper than just maturation rates. Eggs from the DHA group had healthier mitochondrial distribution (100% normal, compared to 0% in the standard diet group) and better-formed spindle structures, which are essential for proper chromosome separation. These improvements appeared even when the DHA-rich diet was started during the period of expected reproductive decline, suggesting it’s not too late to benefit from adding omega-3s to your diet if you’re trying to conceive at an older age.
Good dietary sources include salmon, sardines, mackerel, and algae-based supplements for those who don’t eat fish.
Vitamin B12 and Ovulation
Vitamin B12 deficiency has a direct connection to both infertility and recurrent pregnancy loss. In a clinical analysis of patients with B12 deficiency, prolonged deficiency led to infertility lasting two to eight years, while early-stage deficiency was associated with recurrent miscarriage. The mechanism involves elevated homocysteine levels, which can interfere with implantation and ovulation.
B12 deficiency is more common than many people expect, particularly among vegetarians, vegans, and adults over 40 whose absorption declines naturally. If you’ve been struggling to conceive and eat a plant-based diet, checking your B12 levels is a simple and worthwhile step.
Iron and Ovulatory Fertility
A large study from the Nurses’ Health Study found that women with the highest intake of non-heme iron (the type found in supplements, beans, spinach, and fortified cereals) had a significantly lower risk of ovulatory infertility, with risk dropping by roughly 40% compared to those with the lowest intake. Interestingly, heme iron from red meat and poultry showed no association with ovulatory fertility at all.
This doesn’t mean you need to megadose iron. But if your levels are low, especially if you have heavy periods, correcting that deficiency could improve ovulation. Iron is best absorbed with vitamin C and can cause stomach upset at higher doses, so a prenatal vitamin with iron is often the easiest approach.
Vitamin E and Implantation
For women who have experienced implantation failure, vitamin E supplementation shows promising results. In a 12-week trial, women taking vitamin E had a significant increase in endometrial thickness (gaining about 1.1 mm on average), while the placebo group actually saw a slight decrease. Thicker endometrial lining generally means a better environment for an embryo to implant.
Vitamin E also reduced markers of oxidative stress in the blood, which matters because oxidative damage to the uterine lining and follicular fluid can impair both implantation and egg development. Nuts, seeds, and vegetable oils are the richest food sources.
Inositol for PCOS
If you have polycystic ovary syndrome, inositol deserves special attention. A combination of myo-inositol and D-chiro-inositol in a 40:1 ratio (which mirrors the natural ratio found in the blood of healthy women) has emerged as one of the most effective supplements for improving insulin sensitivity and restoring ovulation in PCOS. In one clinical study, obese women with PCOS who took this combination for six months saw improved insulin sensitivity and ovulatory function.
Inositol isn’t technically a vitamin. It’s a sugar alcohol that your body produces naturally, but women with PCOS often have disrupted inositol metabolism. The 40:1 ratio matters because taking too much D-chiro-inositol relative to myo-inositol can actually worsen egg quality. Many PCOS-specific supplements now use this ratio.
Zinc, Selenium, and Male Fertility
For couples trying to conceive, the male partner’s nutrition matters just as much. A meta-analysis of randomized trials found that zinc supplementation increased sperm concentration by about 1.5 million sperm per mL and improved total motility (the percentage of sperm that move) by 7%. Selenium had an even larger effect on concentration, boosting it by nearly 4 million sperm per mL, while also improving motility by about 3.3% and normal sperm shape by nearly 2%.
These numbers may sound modest, but for men with borderline counts or motility, they can be the difference between a sample that’s viable for natural conception and one that isn’t. Zinc is found in oysters, beef, pumpkin seeds, and lentils. Brazil nuts are one of the richest dietary sources of selenium, with just two or three nuts providing a full day’s worth.
Carnitine for Sperm Motility
L-carnitine and acetyl-L-carnitine, amino acid compounds involved in cellular energy production, improved total sperm motility by about 11% and progressive motility (forward movement) by nearly 10% across multiple randomized trials. These are meaningful improvements for men with unexplained poor sperm movement.
One important caveat: despite the improvements in sperm quality parameters, studies haven’t yet shown a clear increase in actual pregnancy rates from carnitine supplementation alone. The sperm look and move better on paper, but the data on whether that translates to more pregnancies is still limited. Carnitine is found in red meat and dairy, though supplement doses used in studies are typically higher than what you’d get from food.
Putting It All Together
For women, the foundation is a good prenatal vitamin containing folic acid, iron, B12, and vitamin D. Beyond that, CoQ10 and omega-3s are worth considering, especially for women over 35 concerned about egg quality. Women with PCOS should look into myo-inositol and D-chiro-inositol in the 40:1 ratio.
For men, zinc, selenium, and carnitine have the strongest evidence for improving sperm parameters. A high-quality multivitamin covers the basics, but targeted supplementation can address specific deficiencies. Since sperm take about three months to develop, men should start supplementing at least that far in advance of trying to conceive.