Vitamin Ritual

Calcium from food and supplements interferes with heme-iron absorption. Separating these supplements has been advised.

There is some evidence that magnesium may enhance calcium absorption.

One study has shown that taking calcium can interfere with the absorption of phosphorus, which, like calcium, is important for bone health. Although most western diets contain ample or even excessive amounts of phosphorus, older people who supplement with large amounts of calcium may be at risk of developing phosphorus deficiency. For this reason, the authors of this study recommend that, for elderly people, at least some of the supplemental calcium be taken in the form of tricalcium phosphate or some other phosphorus-containing preparation.

Taking vitamin A with iron helps treat iron deficiency, since vitamin A improves the absorption and/or utilization of iron. This interaction has only been shown in a developing country with higher incidence of multiple deficiencies.

Vitamin B6 increases the amount of magnesium that can enter cells. As a result, these two nutrients are often taken together.

Although vitamin C increases iron absorption, the effect is relatively minor.

Vitamin D promotes intestinal absorption of phosphorus.

Vitamin D’s most important role is maintaining blood levels of calcium. Therefore, many doctors recommend that those supplementing with calcium also supplement with 400–1,200 IU of vitamin D per day.

Vitamin E appears to increase intestinal absorption and tissue uptake of vitamin A. Because of this effect, some doctors have used the combination of vitamin E and vitamin A for various skin conditions that are usually treated with vitamin A alone. The addition of vitamin E improved outcomes, while allowing for lower (and safer) doses of vitamin A.

Some evidence suggests that adding vitamin E to fish oil may prevent fish oil-induced increase in blood sugar levels.

Studies in animals and humans suggest that supplementation with large amounts of either vitamin C or vitamin E increases the requirement for the other nutrient.

Zinc competes for absorption with calcium. A multimineral supplement will help prevent mineral imbalances.

High phosphorus intake may impair absorption of iron, copper, and zinc.

Zinc competes for absorption with iron.

Supplementation with zinc, iron, or the combination has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients. This interaction has only been shown in a developing country with higher incidence of multiple deficiencies.