Multivitamin

What multivitamins are and how they work

Multivitamins combine multiple vitamins and minerals in a single formulation, designed to fill nutritional gaps in your diet. These supplements typically contain essential micronutrients like vitamins A, B-complex, C, D, and E, plus minerals such as zinc, magnesium, and calcium. About one-third of adults in the United States take a multivitamin regularly ^[1].

The basic concept is straightforward: provide a broad spectrum of nutrients at levels close to daily recommendations. However, multivitamins are not standardized. Products vary widely in their nutrient composition, dosages, and quality. Some contain nutrients at 100% of daily values, while high-potency formulations may exceed these amounts significantly.

What the research shows

Large-scale clinical trials have produced mixed results. The Physicians' Health Study II followed 14,641 male physicians for over 11 years and found that daily multivitamin use did not reduce cardiovascular events, stroke, or cardiovascular mortality ^[2]. However, the same study showed an 8% reduction in total cancer risk among multivitamin users.

More recently, the COSMOS trials revealed promising findings for cognitive health. A meta-analysis of over 5,000 older adults found that daily multivitamin supplementation improved global cognition and episodic memory over three years ^[3]. These cognitive benefits were most pronounced in participants with a history of cardiovascular disease.

Bioavailability matters

The effectiveness of any multivitamin depends on bioavailability — how well your body absorbs and utilizes the nutrients. Fat-soluble vitamins (A, D, E, K) require dietary fat for absorption, so taking your multivitamin with a meal containing healthy fats improves uptake. Water-soluble vitamins (B-complex, C) are less dependent on fat but still benefit from food intake.

Some formulations use enhanced nutrient forms to improve absorption. Chelated minerals and methylated B vitamins are designed for better bioavailability, though the practical difference varies by individual and specific nutrient.

Who benefits most

Multivitamins appear most beneficial for specific populations. Pregnant women taking prenatal multivitamins show reduced risks of low birth weight and preterm delivery ^[4]. Older adults may experience cognitive benefits. People with restricted diets, malabsorption conditions, or those in food-insecure situations often have the greatest need — ironically, these groups are least likely to take supplements.

For generally healthy adults with balanced diets, the benefits are modest. Multivitamins serve as nutritional insurance rather than a replacement for whole foods. They cannot compensate for poor dietary patterns or unhealthy lifestyle choices.