Avoid or reduce the following:
* Smoking or any other tobacco products.
* Illegal drugs (marijuana, cocaine, PCP, barbiturates or "downers," amphetamines or "speed", LSD, others).
* Exposure to environmental toxins (radioactive materials, anesthetic gas, lead, pesticides, solvents, other chemicals).
* Alcohol consumption (limit to 2 drinks a week if possible).
* Caffeine (limit to 2 cups of coffee a day).
* Any substances containing steroids or testosterone, including some "muscle-building" products. Taking steroids can result in testicular shrinkage and infertility, because these cause the man's body to stop producing testosterone!
* Stress.