What's a healthy diet for dads-to-be? Generally, it should be every bit balanced, varied, and nutritious. Specifically, future dads should:

• Eat plenty of foods rich in vitamin C and other antioxidants; they cut the risk of damaged sperm and boost its motility. An eight-ounce glass of orange juice contains 124 milligrams. Aim for at least 60 mg of vitamin C daily, more — at least 100 mg — if you smoke. (And if you do smoke, consider quitting. See below for reasons why.)

• Get more zinc in your diet, at least 12 to 15 mg a day. Several studies show that even short-term zinc deficiencies can reduce semen volume and testosterone levels. Great sources include extra-lean ground beef (a three-ounce serving has 4.5 mg), baked beans (a one-cup serving has 3.55 mg), and dark chicken meat (2.38 mg per three ounces).

• Increase your intake of calcium and vitamin D. Infertility researchers at the University of Wisconsin at Madison suggest that consuming 1,000 mg of calcium and 10 micrograms of vitamin D each day may improve men's fertility. Good sources of calcium include low-fat milk (an eight-ounce glass has 414 mg) and yogurt (one cup has 302 mg of calcium). You'll find vitamin D in milk (an eight-ounce glass has two mcg) and salmon (a three-ounce serving has eight mcg).

• Cut out or cut back on alcohol. While an occasional drink is generally considered safe, studies show that daily consumption of wine, beer, or hard liquor can decrease testosterone levels and sperm counts, and increase the number of abnormal sperm in your ejaculate.

• Go cold turkey on recreational drugs, such as marijuana and cocaine. Marijuana can decrease your sperm's motility and, like cocaine, it can affect the brain chemistry responsible for releasing reproductive hormones. Drug use can also cause birth defects.

Besides food, what other factors should I be aware of?
A host of lifestyle factors can be perilous to your potency. The good news is, once you become aware of these often hidden fertility drainers, they are fairly easy to avoid. Here's a sampling of the worst offenders:

• Hot tubs, saunas, and tight-fitting clothes. Testicles function best when they keep their cool. "The boys" are happiest at 94 to 96 degrees, which is a couple of degrees cooler than normal body temperature. Steamy spa equipment, snug jeans, synthetic shorts, and bikini underwear can all overheat your testicles and inhibit sperm production. To protect your swimmers, wear loose fitting pants and boxer shorts (the truth is, they look better, too).

• Bicycle seats. Impotence can be an unexpected and frightening side effect of avid cycling. A study from the University of Southern California School of Medicine found that a bicycle seat's steady pressure on the groin area can damage arteries and nerves. There are some new ergonomic seats designed to alleviate this pressure. (See some examples made by Specialized on their Web site.) It also helps to periodically lift yourself off your seat when riding long distances. Visit your doctor if you feel any numbness or pain or have erection problems after biking

• Rough sports such as football, hockey, soccer, basketball, baseball, horseback riding, and even sex. The danger here is traumatic injury to the genitals, which can hurt your ability to produce sperm or ejaculate. If you do play contact sports (the ones that require clothes, anyway), wear protective gear. When you're training for the bedroom Olympics, just remember: Gentle is best when your goal is a baby.

• Stress. Studies from the Department of Physiology at the Medical College of Ohio show that even minimal stress can cause a man's testosterone levels and sperm count to drop. Chilling out can power up your potency.

• Workplace hazards. Exposure to radiation and chemicals can damage sperm, lower sperm counts, and cause genetic defects in children, according to research from McGill University in Montreal. If you're exposed to any hazards on the job, ask for a temporary reassignment.

• Certain medications. Ask your doctor about the sexual side effects of any prescription drugs you are taking. Many medications, including those used to treat blood pressure, ulcers, cancer, seizures, colitis, irritable bowel syndrome, and even bacterial infections can cause fertility problems and lower sperm counts.

• Stop smoking. Do you need one more reason? Well consider this: Recent research confirms that men who smoke have fewer sperm in their ejaculate. Plus, kicking the habit now can help your family out later. Second-hand smoke is dangerous for your partner and your unborn child.