Select Vitamins and Minerals in the Management of Diabetes
The use of vitamin, mineral, and other complementary nutrition-based therapies has increased dramatically in the United States. Many health care providers are also beginning to explore the use of these therapies in their practices. For those of us who work in conventional health care settings, this is a new venture. But for many of our patients who have been self-medicating with supplements, it is not. This article reviews how micronutrient requirements are determined and summarizes current recommendations for supplementation and the most pertinent research on the use of key vitamins and minerals in diabetes management.
Vitamins and minerals play diverse roles in our bodies. Initially, the nutrition community focused on the roles micronutrients play in preventing deficiency diseases such as scurvy, pellagra, and rickets. As our understanding of nutritional science grew, it became clear that nutrients act in far broader ways. We now know that micronutrients can regulate metabolism and gene expression and influence the development and progression of many chronic diseases. Eventually, we may be able to tailor nutritional recommendations to individuals’ unique genetic makeup, thus increasing the potential benefit and positive outcomes of medical nutrition therapy.
Micronutrients are vitamins and minerals that our bodies require in small quantities for specific functions. They most commonly function as essential coenzymes and cofactors for metabolic reactions and thus help support basic cellular reactions (i.e., glycolysis, the citric acid cycle, lipid and amino acid metabolism) required to maintain energy production and life. Even moderate deficiencies can lead to serious disease states. Micronutrients have been investigated as potential preventive and treatment agents for both type 1 and type 2 diabetes and for common complications of diabetes.
Micronutrient requirements can be difficult to determine because many noninvasive assessment methods, such as the measurement of plasma nutrient levels, do not accurately reflect the quantities of nutrients present in functionally important nutrient pools, and many dietary assessment methods and databases are not perfectly accurate.
These and other methodological concerns have limited researchers’ ability to conduct well-designed, targeted studies of micronutrient supplements in individuals who are deficient and therefore most likely to benefit from supplementation. This has likely contributed to the varied results obtained in research studies of micronutrients in people with diabetes.
Other research variables that may also contribute to the lack of consensus in study results include the use of diverse populations of patients with diabetes stemming from different biochemical origins, differences in glycemic control, variations in doses and forms of micronutrients used, variable study length, lack of control for dietary contribution of micronutrients, and use of different biochemical assays and methods of analysis. We are unlikely to have conclusive data until these methodological concerns are resolved.
The American Diabetes Association (ADA) and the American Dietetic Association recommend that healthy people at low risk for nutritional deficiencies meet their nutritional requirements with natural food sources. These organizations do not generally support the use of micronutrient supplements for people with diabetes, and the supplements they do recommend are the same as those recommended for the general public. The ADA does note that people who are at increased risk for micronutrient deficiencies, such as those following very-low-calorie diets, the elderly, strict vegetarians, and other special populations, may benefit from multivitamin supplements.
Current nutritional guidelines are based on Dietary Reference Intakes (DRIs). DRIs, established in 1998, expand on the previously used Recommended Dietary Allowances (RDAs). DRIs are composed of four values: the RDA, the Adequate Intake (AI), the Estimated Average Require-ment (EAR), and the Tolerable Upper Intake Level (UL).
The RDA is the level of nutrient intake believed to meet the needs of nearly all healthy individuals. It is most appropriately used as a target intake goal. However, intakes that fall below the RDA are not necessarily deficient because the RDA, by definition, is significantly greater than the needs of many people. The AI is used in place of the RDA for nutrients for which we do not yet have sufficient scientific evidence to establish an RDA.
The EAR is the level of nutrient intake believed to meet the requirements of half of the healthy individuals in a given life stage or gender group. It is most appropriately used to assess the likelihood of a nutritional deficiency. Diets that fall below the EAR for a given nutrient have a ≥50% chance of being inadequate. Supporting clinical and biochemical evidence is needed to establish the presence of an actual deficiency.
The UL is the greatest level of nutrient intake for which no adverse side effects have been noted. It is based on the members of a healthy population who are most likely to experience toxicity. The UL is usually based on total daily nutrient intake from both food and supplements. It is most appropriately used to assess the level of chronic daily nutrient intake that is likely to cause significant negative side effects.
Vitamin and mineral supplements are regulated by the Food and Drug Administration under the 1994 Dietary Supplement Health and Education Act (DSHEA). This act provides for only minimal regulatory oversight of supplement manufacturing and processing, focusing instead on the labeling and marketing of these products.