Vitamins and minerals are a vital part of a healthy diet. If a person eats a variety of foods, the likelihood of developing a deficiency of these nutrients is very small. However, people who follow restrictive diets may not get enough of a particular vitamin or mineral. For example, strict vegetarians may become deficient in vitamin B₁₂, which is available only in animal products. On the other hand, consuming large amounts (megadoses) of vitamin and mineral supplements, without medical supervision, may have harmful (toxic) effects. Source: The Merck Manual Home Edition
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