A large meta-analysis of multivitamin supplementation published in the Annals of Internal Medicine found no evidence that multivitamin supplements reduce the risk of cardiovascular disease, cancer, or all-cause mortality in the general population. This finding is consistent across dozens of individual trials of individual and combined vitamin supplementation. It contrasts starkly with the consistent evidence that dietary quality from whole food sources does reduce all of these outcomes.
Why Isolated Nutrients Behave Differently from Food Nutrients
In food, nutrients exist within a complex matrix of cofactors, transport proteins, and synergistic compounds that regulate their absorption, metabolism, and biological activity. Vitamin E in almonds is accompanied by selenium, which regenerates spent vitamin E molecules. Beta-carotene in carrots is embedded in a fibre matrix that regulates its absorption rate. Curcumin in turmeric is co-consumed with piperine which dramatically increases its bioavailability. Supplemented nutrients are isolated from these synergistic contexts and do not replicate the same biological behaviour.
When Supplements Are Appropriate
Supplements fill specific, defined nutritional gaps that cannot be met by food in specific circumstances. Vitamin D supplementation is appropriate and well-evidenced for adults in northern latitudes with limited sun exposure. Vitamin B12 supplementation is essential for strict vegans. Iodine supplementation may be appropriate for adults avoiding all dairy and seafood. Omega-3 supplementation is appropriate for those who cannot or will not eat oily fish. These targeted supplementation strategies address defined deficiencies. They do not replace the comprehensive nutritional benefit of a whole food dietary pattern.