In a variety of tests, garlic and onions (members of the allium family) have been shown to reduce cholesterol, high blood pressure and the incidence of flu. For example, Alan Tsai, Ph.D. with the Michigan School of Health, has tested rats and humans for the effects of garlic on cholesterol levels. He fed test groups high cholesterol diets, with one group receiving garlic. Those who consumed garlic had cholesterol levels that rose about 4 percent and had lower blood pressure naturally with garlic, as opposed to those without garlic whose cholesterol levels rose 23 percent. Dr. Tsai noted that the incidence of cardiovascular and other diseases is lower in countries whose populations consume large amounts of garlic, though he was reluctant to attribute this effect solely to garlic.