 Yes, coffee may reduce cancer risk, but what about the caffeine? Oh, you mean the substance that increases energy availability and expenditure, decreases fatigue in the sense of effort associated with physical activity, enhances physical motor and cognitive performance, increases alertness, wakefulness, and feelings of energy, decreases mental fatigue, quickens reactions, increases their accuracy, increases the ability to concentrate, focus attention, and enhances short-term memory, the ability to shelve problems, the ability to make correct decisions, enhancing cognitive functioning capacities, and neuromuscular coordination. And, in other words, healthy, non-pregnant adults is safe. That caffeine? What do they mean by moderate amounts, though? Up to 1,000 milligrams, about 10 cups of coffee a day. What about this, though? A case of fatal caffeine poisoning. 21-year-old woman, 10,000 milligrams of caffeine by swallowing a bottle of caffeine pills. The equivalent of about 100 cups of coffee at one time is, indeed, too much. The non-pregnant is an important caveat, though. New advice has been issued to restrict caffeine intake and pregnancy to under just 200 milligrams a day.