Anything that hurts a man's health hurts his sperm. The good news: preserving your reproductive potential will also keep you healthy.
Protect Your Heart: "What's bad for your heart is bad for your penis," says Columbia's Harry Fisch. Erections depend on arterial flow from the heart, and when that's reduced or blockage occurs, erectile dysfunction (ED) is often close behind. Get an annual physical, including a heart checkup and a cholesterol test, once you reach your 30s. If your cholesterol is high, cholesterol-lowering medicine may help.
Stay Active: "If you're trying to have a child in your 30s, 40s, or 50s, getting into the best shape of your life will give you the highest testosterone level possible," says Fisch.
Watch Your Weight: Potbellies and excessive waist size are often telltale signs of heart disease. They also generate heat that can reach the testicles, decreasing the testosterone in sperm. In general, the bigger the belly, the lower the testosterone. Eat a balanced, low-fat diet, and reduce your calorie intake.
Take Antioxidants: Vitamins C or E, since they may help battle free radicals that play a part in breakdown of sperm DNA.