There is also evidence that a multivitamin supplement improves immune status in healthy elderly persons. Vitamin A deficiency is uncommon except with prolonged starvation. Higher intakes are not recommended because the resulting hypercalcemia rapidly increases the toxicity. Vitamin D is also produced by exposure to moderate direct sunlight, although such exposure can have photoaging and carcinogenic effects on the skin. Synthetic forms of vitamin D are under study.
Vitamin E is a common supplement.
This high dose also acts as an anticoagulant, which may lower the risk of myocardial infarction. Whether the high dose increases the risk of bleeding remains unclear. Vitamin E improves cellular immune function, which potentially lowers the risk of infection. Vitamin E complex, which contains various subtypes of vitamin E, may be more beneficial than -tocopherol alone. Thiamine deficiency usually occurs with deficiency of the other B vitamins.