A very large study followed the exercise habits of more than 13,000 men and women for eight years. Less fit individuals died, mainly from heart disease and cancer (7). In other research, exercise has been shown to help prevent osteoporosis (8) and some forms of diabetes (9), treat high blood pressure (10) and painful menstrual cramps (11), and control weight (12).

Part of the problem, of course, is encouraging people to exercise. Some employers have taken it upon themselves to offer their workers fitness programs. The results are positive. Not only are employees more fit, but the company saves money with less on-the-job injuries, reduced absenteeism and lower health care costs (13).

4. Smoking
One way people try to control stress is by smoking. This short term solution, however, has many life-long consequences, not only for you but your offspring as well.

Past studies have linked cigarette smoking during pregnancy to behavioral problems (14) and impaired intellectual development (15) in children. A 1994 investigation from the Universities of Kentucky and Wisconsin confirmed that it's not just smoking that harms unborn children but how long the mother smokes. Undoubtedly non-smoking mothers deliver fewer low weight and premature babies than smoking women. However, women who quit during their first trimester, have healthy infants than women who smoked throughout pregnancy (16).

Adults who decide to smoke live shorter and sicker lives. Besides cancer, smoking increases your risk of heart disease, peptic ulcers, problems with pregnancy (17), decreases insulin effectiveness (18) and impairs immunity (19). Those who elect not to smoke, but are exposed to second-hand smoke suffer almost as much.

Parents who smoke around their small children have been accused by some of child abuse. These kids suffer from more ear infections, colds, pneumonia and illness in general than their unexposed playmates (20).

In adults, passive smoking increases your chance of heart disease. Recently, researchers at the University of California in San Francisco offered one explanation for this. Scientists placed rats in a smoke filled cage for six hours a day, five days a week. The longer the rats breathed in smoke, the larger were their myocardial infarcts, necrotic areas in the heart (21).

5. Alcohol
Alcohol is another substance we use to temporarily relieve stress. While research says that the occasional glass of wine decreases the incidence of coronary heart disease, in the larger scheme of things alcohol is anything but health promoting.

Almost 25 years ago, a group of New York investigators explored why alcoholics are more susceptible to sickness than the general population. One reason for this, they discovered, was diminished immunity (22). On top of this, alcohol tends to wash away nutrients, damage various organ systems such as the liver, cause some cancers, promote hypoglycemia (particularly in diabetics), and, ironically, hurt the heart when consumed in large quantities.

Early alcohol exposure, as in the womb, can result in fetal alcohol syndrome, a condition where a small brain, low IQ and poor judgment are evident. This disorder continues on into adulthood (23).

People who drink as grownups also risk brain damage. A Danish study confirmed what we've always suspected: chronic alcoholism destroys white matter in the brain. This damage may be reversible in alcoholics who quit drinking (24).