In fact, they may have a completely opposite effect to the one intended. Recent research suggests that heavy supplementation may increase the risk of cancer. In this form, they are damaging to our health. By contrast, a balanced, varied diet provides the quantities our bodies need - naturally. Nevertheless, I believe it's a good idea for everyone to have a single mineral-vitamin capsule daily.
Variations exist, however.
Seek professional advice on the appropriate choice. Certain groups and individuals may require supplementation. Anaemia due to iron deficiency is common in children. Other supplements for children may include Vitamin K, mostly given to newborn babies to prevent bleeding tendencies. Vitamin B12 is given to babies of vegan mothers, because plant foods have no Vitamin B12, and the foetus may thus be at risk of pernicious anaemia.