What is known about the safety of multivitamin-multimineral supplements for the generally healthy population? Theoretical basis for harm

Abstract

Assessment of the safety of nutrients presents a challenge different from that posed by the assessment of other chemicals in food such as additives or contaminants. Because nutrients are essential, a dose-response relation exists at both ends of the intake range, separated by a safe range of intake that reflects normal homeostatic processes. The safe intake may not be the same for all population groups and life stages. The size of the safe intake range for each nutrient will vary and in a few cases may be very small. Certain nutrients such as vitamin A and manganese have known and potentially serious adverse effects at high intakes, whereas others such as iron or vitamin C may have more minor adverse effects that are readily reversible and may only be associated with supplement intake. The risk of harm occurring from taking dietary supplements will depend on the safe intake range of the nutrient concerned, the susceptibility of the individual, and the likely intake of the same nutrient from other supplements or the rest of the diet. In many cases, the available database for the safety of nutrients is very limited because the studies, where available, were not designed to assess adverse effects but may have detected problems when they occurred. Further information on the safety of nutrients could be obtained through careful experimental design.

13-cis-Retinoic acid specific down-regulation of angiotensin type 1 receptor in rat liver epithelial and aortic smooth muscle cells

“…Other retinoids are shown to have increased toxicity at high doses, particularly if consumed as preformed vitamin A (Mulholland & Benford 2007). In fact, adverse effects may be observed with intake of retinol equivalents of only 1500 mg, which is less than twofold greater than the recommended daily allowance.…”

Analytical ingredient content and variability of adult multivitamin/mineral products: national estimates for the Dietary Supplement Ingredient Database ,

“…In our study, the products with the 6 nutrients that were labeled above their ULs had low market shares. Thus, such products are less likely to lead to overexposure at the population level, although they still may be a concern for individual consumers (45) and increase their risk of adverse interactions [e.g., between MVM and prescription medicines (46,47)]. …”

Multivitamins : Use or Misuse?

“…For vitamins to cause side effects the intake should exceed recommended daily allowance several fold (Table 3). Excess intake may occur if single vitamins are taken in addition to multivitamins [22]. The vitamins and micronutrients for which excess intake has been reported are vitamin A, vitamin C, niacin, iron and zinc [23].…”