2 CHOLESTEROL Chapter One Well over 100 million Americans—about 17 percent of the population—have moderate to high cholesterol levels. Of these, more than 37 million have cholesterol levels that place them at high risk of developing heart disease. But the fact remains, not all cholesterol is bad. In fact, the body needs cholesterol for: • the production of vitamin D; • the formation of sex hormones such as estrogen, testosterone, and ­ progesterone; • the production of bile acids that help us digest food; • the formation and maintenance of cell membranes. If cholesterol is so important, then why is it considered so dangerous. Because when there is too much, it can encourage plaque buildup. Plaque is a combination of substances including fat and cholesterol.When plaque builds up, the artery narrows, constricting blood flow to the heart. Plaque can even build up to the point where blood flow is completely blocked.This condition, known as atherosclerosis, can significantly increase the risk of heart attack and stroke. Of course, while cholesterol isn’t the only factor that can block arteries, it remains a key concern for many Americans.