Abstract
In the early part of the last century, vitamins were mainly used to fight against nutritional deficiencies, which caused diseases like beriberi, rickets, and scurvy to be commonplace. While such deficiencies are now rare in the developed world, they can be found in developing countries, for example, blindness caused by vitamin A deficiency.
Key points
North American population is well nourished, so severe deficiencies are rare
Deficiencies of selected vitamins and minerals do occur, especially D and folate
Primary prevention of chronic disease with supplementation in well-nourished individuals is probably not beneficial, but unlikely to harm
Increase vegetable/fruit intake to between 5 and 9 servings per day
Get some sun — aim for 15 minutes every day
Dr. L. Maria Gutschi, a lipid clinic pharmacist with the Canadian Forces Health Support Unit in Ottawa, briefly traced the history of vitamin research for the audience attending her session on nutritional supplements, before moving on to the topic of present vitamin deficiencies. The most common deficiency states for vitamins in North America are folate and vitamin D, while worldwide these are folate and vitamin A. Various diseases, especially gastrointestinal, can cause nutrient deficiencies, as can different drugs, such as diuretics, anticonvulsants, corticosteroids, chemotherapy, and more. People who are at risk of vitamin deficiencies include the elderly, those with digestive tract disease, smokers, alcoholics, pregnant and breastfeeding women, vegetarians and vegans, and those with limited sun exposure or limited milk intake.
Folate supplementation is especially important during times of rapid cell division, such as pregnancy and infancy. Deficiency of this nutrient is associated with neural tube birth defects, folate-deficiency anemia, and possibly with early childhood cancers. And it has been shown recently that people who live in northern latitudes have suboptimal levels of vitamin D, which could lead to various conditions and diseases.
Dr. Gutschi's session also examined the evidence that exists for using vitamins and minerals for primary prevention of chronic disease. Are supplements actually effective? Or could they even be harmful?
While recent studies have shown evidence that some antioxidants, such as beta carotene and vitamin A, may actually increase mortality, there are a few areas where supplementation has a proven benefit, such as taking calcium and vitamin D for osteoporosis. Another disease that has firm evidence for a benefit from vitamins is age-related macular degeneration (AMD). The Age-Related Eye Disease Study (AREDS) found that while the antioxidant and zinc formulation that participants in their study took had no effect on primary prevention of AMD, it had a definite effect on secondary prevention — it helped prevent those patients with AMD from progressing to the advanced stage of the disease, and also helped them preserve their existing visual acuity.
On the whole, though, if we think that vitamins might prevent diseases such as cancer, Dr. Gutschi says, we may be overly optimistic, as the data are not well established as to any benefit. She did acknowledge that the recent press about vitamin D being a cancer fighter was very interesting, but the article behind this excitement had not yet been published at the time of this session and so was not included. [The double-blind, randomized placebo-controlled trial was published in the June issue of The American Journal of Clinical Nutrition, and found that improving calcium and vitamin D nutritional status substantially reduced all-cancer risk in postmenopausal women.] Dr. Gutschi pointed out that it is important to keep up with the literature, as new studies are constantly appearing.
When counselling patients about supplements, pharmacists should first determine if there is the possibility of vitamin or mineral deficiency — be on the lookout for dietary extremes (for example, vegetarians, and especially vegans, might have zinc, iron, B12, and B6 deficiencies). Other causes of nutrient deficiencies include alcoholism, chronic gastrointestinal disease, or drugs. Check to see if patients have chronic diseases that might benefit from supplements. But caution them against excess supplement intake, especially of iron, zinc and vitamin A, which can cause liver damage.