Potentially harmful side effects

The practice of taking dietary supplements is generally harmless, as the body is able to excrete most excesses. However, there are cases where supplements can be harmful. This occurs when there are excessive intakes, especially of iron, fat-soluble vitamins and energy.

Iron overload is not common but can occur when iron supplements are taken in excess. This can cause damage to liver tissue. When high iron intake is combined with high doses of vitamin C, more iron is absorbed and can be released as free iron, able to cause damage by oxidation of essential molecules. The oxidation of LDL by free iron can be a cause of heart disease.

Accidental poisoning occurs when young children take excessively large doses of vitamins and minerals, with the most fatalities occurring in children under six taking high-potency iron supplements, which are especially toxic.

Fat-soluble vitamins in large doses can accumulate in body fats to levels where symptoms of excess become apparent, mostly with vitamin A, which can cause liver disease.

There is also a question of standards and dosage in vitamin, mineral and herbal preparations. Who knows what exact dosage of each micronutrient or phytochemical should be included? Self-administration means that those who take these supplements have not been assessed as to their needs, and the manufacturers can't possibly know the nutritional requirements of the consumers. Surveys of people who take supplements have shown they often take those supplying the nutrients they need least, and don’t supply the nutrients their diets are missing.

Another concern is that supplements can be seen as an excuse for continuing with poor eating habits, in the belief that they will compensate for any imbalance or deficiency.