Being underweight or overweight can have negative effects on a man’s sperm, and it can kill a couple’s sex life because weight problems can affect a man’s libido and performance. Sticking to a healthy diet that contains a good mix of fruits, vegetables, lean proteins, grains, and dairy, and fitting in physical activity on most days of the week can help him reach or maintain a healthy weight.

Folic acid isn’t important just for moms-to-be. Men who had lower levels of folic acid in their diet had a higher rate of abnormal chromosomes in their sperm, according to a study by researchers at the University of California, Berkeley. When sperm with abnormal chromosomes fertilize an egg, it may result in miscarriage or birth defects. More than half of first-trimester miscarriages are caused by chromosomal abnormalities in the embryo. This doesn’t mean your guy has to take folic acid pills: Foods that are high in folate, like beans, leafy green vegetables, whole grains, citrus fruits, and folate-enriched cereals, breads, and pastas, will help him get the recommended 400 milligrams of folic acid he needs daily.

In a 2019 study, researchers at Aarhus University in Denmark associated earlier bedtimes with improved sperm quality. The key seems to be going to bed before 10:30 pm. The researchers also found a link between getting sufficient sleep—between seven-and-a-half and eight hours per night—with improved fertility.

It takes two to create a healthy embryo, so if women should take prenatal vitamins, so should men. Men should start taking these supplements six months before conception to set the stage for their sperm to be strong, healthy, mobile, and less clumpy, suggests Sherry Ross, M.D., Ob-Gyn, author of She-ology: The Definitive Guide to Women’s Intimate Health. She says these vitamins should include B12, Vitamin C, Vitamin E, Zinc, and Selenium. “Zinc is helpful in maintaining normal testosterone levels. Selenium has been shown to reduce the risk of birth defects and improving low sperm counts. There is no downside to being your healthiest self while trying to conceive with your partner.”

Smoking cigarettes can cause low sperm counts and slow-moving sperm so your guy should quit, preferably at least three months before you try to conceive. “Sperm production takes about three months, so any changes the man makes today won’t show up in the semen for at least three months,” says Suzanne Kavic, M.D., director of the division of reproductive endocrinology at Loyola University Health System. He should also nix marijuana or other illicit drugs as sperm may be damaged by these drugs, and women are more likely to miscarry if their partners use recreational drugs like cocaine, marijuana, and any of the other typical amphetamines.

He doesn’t have to give it up completely, but it’s a good idea for men to limit their alcohol intake if they hope to become a dad. Alcohol has been shown to reduce sperm production and cause sperm abnormalities. Dr. Kavic says one to two drinks a day is fine (as long as they’re normal-size servings!). Another reason he should dry out a bit: A lot of men don’t perform as well sexually when they’re inebriated, Dr. Kavic says.

A thorough checkup before trying to conceive will give him an overview of his health and fertility status. As in your pre-conception visit, he can expect discussions about his body mass index (BMI), any medications he uses, lifestyle factors that may affect fertility and pregnancy, any genetic disorders or history that may pose a risk to the future baby, and what he can do to ensure you have a healthy pregnancy. He will also be given any needed immunizations to help prevent him from passing on illnesses like chickenpox and the seasonal flu to you during pregnancy.

A study of Danish men found that sperm count and sperm concentration were slightly reduced in men who had a high soda and/or caffeine intake. Dr. Mazzullo says men should limit their caffeine consumption (that includes coffee, tea, chocolate, and energy drinks) to 300 milligrams a day (about three 6-ounce servings).

Stress can increase abnormal sperm and reduce its concentration. Sleeping and eating well, exercising regularly to work off pent-up energy and tension, making time to hang out with his guy friends (or sit in front of the tube and do nothing!) and other activities that he finds enjoyable or relaxing can help keep his stress in check.

Before you start trying to conceive, he should make a list of all the medications he takes—including prescriptions, over-the-counter drugs, vitamins, and herbal supplements—and check them with his doctor. Some medications can affect the quality or quantity of a man’s sperm. If he’s using a medication that could possibly interfere with your baby-making goals, his doctor should be able to recommend a more fertility-friendly alternative.

There’s a reason a male’s testicles hang outside of his body. “Sperm production has to take place at a certain temperature, and even our core body temperature is too hot, so the testicles are outside to keep cool,” explains Dr. Kavic. If your guy does something that overheats his testicles, it can interfere with sperm production. So he should limit the time he spends in hot tubs, saunas, and steam rooms. Dr. Mazzullo recommends that men keep it to 15 minutes, no more than twice a week.

He may want to change his laptop habits, too. Dr. Kavic says there’s a possibility that using a computer on his lap too often may cause genital warming that could possibly affect the sperm. His best bet? Keep the lap time to a minimum, invest in a laptop cooling pad, and use the laptop on a desk more often.

If your guy works around a lot of chemicals and toxins, he needs to make sure they don’t do a number on his member. Toxic chemicals such as heavy metals, lead, and chemical solvents can increase the percentage of damaged sperm, so men who expect to conceive in the near future should try to avoid them. If his job places him around chemicals, he can limit his contact by wearing a face mask and protective clothing and always using proper ventilation.

In October 2013, the Biology of Reproduction Papers-in-Press published research highlighting the link between walnuts and fertility. In particular, eating 75 grams of walnuts daily was found to improve “sperm vitality, motility, and morphology”—maybe because of the antioxidants, micronutrients, and alpha-linolenic acid (ALA) found in walnuts. The research was conducted on healthy men between 21 and 35 years of age.