One might think that more is better when taking nutrient supplements. However, a nutrient taken in concentrated amounts or in megadoses can be dangerous. Overdoses can happen easier with supplements than with food. Minerals in large amounts can be toxic as can vitamins. Excessive doses of these vitamins can accumulate and be harmful.
Dangerous levels can produce such symptoms as nausea, vomiting, and other serious side-effects.
Toxicity from water-soluble vitamins, such as vitamin C, is unlikely since excess amounts are flushed from the body in the urine. However, serious side effects can occur even with water-soluble vitamins. Because nutrients interact with each other, a balance of all nutrients is important. If the body has too much or too little of any nutrient, the body's use of these nutrients may be altered. Additional supplements should never be used to replace a missed meal.