colon, which prompted newspaper and magazine stories cautioning against coffee drinking. However, further investigations have exonerated coffee drinking; it appears that cigarette smoking was to blame for the increase in bladder cancer cases, and some other dietary factor, such as fats, may be at work with colon cancer.
Over the past few years, a number of studies have found that coffee drinking may increase LDL-cholesterol levels, especially when the coffee is boiled (as it is in Scandinavia). But at least among U.S. coffee drinkers, the effect is so small as not to increase the risk for heart disease. Tea drinking has no effect on serum cholesterol levels, nor does it increase the risk of heart disease.
In humans, caffeine crosses the placenta. In addition, the body metabolizes caffeine one-third as fast during pregnancy. As a result, caffeine accumulates in the mother, and it passes to the fetus, which has no enzymes with which to get rid of this chemical. What caffeine does to the human fetus is unclear, but some studies have shown that pregnant women who have high caffeine intakes are at greater risk of delivering babies of low birth weight. It appears sensible to limit caffeine intake during pregnancy.
Nearly 3,000 substances are added intentionally to foods in the United States during processing. Some 12,000 chemicals, such as the food packaging material polyvinyl chloride, can enter food more or less by accident; these are called indirect