Sometimes too much of a good thing can become a very bad thing indeed. In an earnest attempt to consume a healthy diet, dietary supplement enthusiasts have been known to overdose. Vitamin C, for example, long thought to help people ward off cold viruses, is currently being studied for its possible role in warding off cancer and other diseases that cause tissue degeneration. Unfortunately, an overdose of vitamin C – more than 10,000 mg. – on a daily basis can cause nausea and diarrhea. Calcium supplements, commonly taken by women, are helpful in warding off osteoporosis. More than just a few grams a day, however, can lead to stomach upset and even kidney or bladder stones. Niacin, proven useful in reducing cholesterol levels, can be dangerous in large doses to those who suffer from heart problems, asthma, or ulcers.
The main idea expressed in this paragraph is
A.supplements taken in excess can be a bad thing indeed.
B.dietary supplement enthusiasts have been known to overdose.
C.vitamins can cause nausea, diarrhea, and kidney or bladder stones.
D.people who take supplements are preoccupied with their health.
A ?