Micronutrients in Health and Disease: At–Risk Populations

Certain groups are likely to be deficient in micronutrients and to need dietary adjustments or supplementation. The following nutritional choices may result in poor or deficient intakes of essential nutrients:

Alcohol abuse. Lower blood concentrations of vitamins C and E, carotenoids, and selenium have been found in alcohol–dependent patients, compared with low–alcohol consumers.^35,36 Alcohol abusers may miss B vitamins through poor food intake and may lose B vitamins due to the diuretic effect of alcohol; these (particularly thiamine) must be replaced in order to prevent neurologic sequelae, including Wernicke–Korsakoff syndrome.³⁷ Folate intake may be especially important for alcohol consumers. For example, individuals who consume as little as one–half of a serving of alcohol per day appear to be at twice the risk for breast cancer when folate intakes are below recommendations (ie, at <335 μg/day), compared with those with higher intakes.³⁸

A Western dietary pattern. Individuals who eat a Western diet based on animal products generally have reduced intakes of several micronutrients, compared with individuals following plant–based diets, although these reduced intakes may not represent frank deficiencies. Vitamin C deficiency has been found in individuals who eat meat–based diets and shun fruits and vegetables.^9,39 In the European Investigation into Cancer and Nutrition study of 65,429 men and women, individuals avoiding meat and other animal products had much higher intakes of fiber, folate, and vitamins C and E, compared with omnivores.⁴⁰ Other surveys of vegetarians also determined higher intake of vitamins C and E, in addition to potassium⁴¹ and dietary fiber,⁴² compared with omnivores. Pregnant vegetarian women had significantly lower risk for folate deficiency than omnivores.⁴³

Smokers. Smokers often have poorer diets in general than nonsmoking individuals, and generally consume fewer fruits and vegetables and more saturated fat.⁴⁴ Moreover, even after adjustment for differences in diet, smokers have significantly lower blood levels of several carotenoids and vitamin C.⁴⁵

Inappropriately restricted diets. Nutritional deficiency can result from overly stringent dietary restrictions, particularly those that suggest elimination of the most nutrient–rich foods (eg, vegetables, fruits, and whole grains). Such diets may be practiced by individuals who are dealing with what they suspect are problematic reactions to foods^46,47 and who do not seek alternative sources of essential nutrients. Individuals who consume low–carbohydrate, high–meat diets may have vitamin C intakes that are nearly 50% lower than those of persons eating more plant–based diets,⁴⁸ and individuals eating Western diets also have relatively poor carotenoid intakes. According to the Institute of Medicine, current and international dietary guidelines call for obtaining at least 90% of vitamin A in the form of provitamin A carotenoids, and U.S. residents obtain less than 40%, with the balance coming from animal products.²⁵ This results in lower blood levels of carotenoids, and these reduced levels are consistent with a greater risk in these people for many chronic diseases, compared with individuals eating recommended amounts (ie, > 5 servings/day) of fruits and vegetables.²⁵

Elderly persons, particularly those in hospitals or long–term–care facilities, and individuals following unsupplemented vegan diets are at risk for deficiency of vitamins D and B₁₂. With appropriate supplementation, a vegan diet has nutritional advantages, compared with unmodified diets.⁴⁹ Alcohol–dependent individuals are at risk for folate, B₆, B₁₂, and thiamin deficiencies. Poor intakes and subclinical deficiencies in these and other groups, and the increased risk for chronic diseases that may follow have led to the suggestion that all adults take a multiple vitamin daily.⁵⁰

Vitamin dependency disorders resulting from inborn errors of metabolism are rare, but they require lifelong treatment with certain vitamins. Examples of these include multiple carboxylase deficiencies that are biotin–responsive⁵¹ and pyridoxine–dependent seizures.⁵²