In one study, patients with coronary heart disease were randomly assigned to two different 16-week courses. One group took a course in health education, which included discussion of the impacts of stress, diet, and exercise on heart disease. The other group took a course in transcendental meditation. Transcendental meditation involves the use of a mantra, the repetition of a phrase or syllable, in order to quiet the mind.
At the conclusion of the courses, the group that practiced meditation lowered several of their risk factors for heart disease. They lowered both their blood pressure and their resistance to insulin. Insulin resistance means that cells that need insulin are unable to use it. When insulin resistance is lowered, these cells can then use insulin in order to pick up glucose from the bloodstream. This lowers their blood glucose levels, which is important in lowering the risk of heart disease.
Lifestyle factors such as physical activity and diet certainly play important roles in determining a person's risk of heart disease, but so does stress. Stress causes the body to release hormones that increase insulin resistance. Meditation counteracts this effect of stress on insulin resistance.
Although transcendental meditation is the only method of relaxation so far to be shown to produce these specific benefits in reducing the risk of heart disease, other forms of relaxation, such as yoga or tai chi, may prove similarly beneficial.
So for your heart's sake, learn to relax.