What are vitamins?

Vitamins are organic micronutrients required in small amounts to support metabolism, growth, and the maintenance of normal physiological function. They do not provide calories but act as coenzymes, cofactors, antioxidants, and signalling molecules that enable biochemical reactions. Because many vitamins cannot be synthesized in adequate quantities by the body, they are considered essential and must be obtained from food or supplements when diets are inadequate.

Classification and forms

Vitamins are classified by solubility: water-soluble (the B-complex group and vitamin C) and fat-soluble (A, D, E, K). Water-soluble vitamins are generally not stored in large amounts and excesses are excreted in urine; fat-soluble vitamins are absorbed with dietary fats and may accumulate in liver and adipose tissue. Supplement formulations reflect these properties through delivery choices (oily suspensions or emulsions for fat-soluble vitamins, tablets or effervescents for water-soluble types) and by using specific chemical forms that influence bioavailability—examples include methylcobalamin for B12 or 5-methyltetrahydrofolate for folate.

When supplements may be appropriate

Supplements can help fill dietary gaps in situations such as restrictive diets, limited sun exposure (affecting vitamin D synthesis), malabsorption disorders, increased physiological demand (pregnancy, growth, illness), and when laboratory testing identifies a deficiency. Evidence-informed use focuses on correcting documented shortfalls or meeting increased needs rather than routine high-dose supplementation in otherwise replete individuals. For an accessible primer on foundational concepts, see the article What are vitamins?.

Recognizing deficiency and monitoring

Clinical signs of deficiency vary by nutrient: vitamin B12 deficiency can cause hematologic and neurologic symptoms; vitamin D insufficiency is associated with suboptimal bone health and muscle weakness in some people; vitamin C deficiency leads to scurvy in severe cases. Laboratory testing (for example, serum 25-hydroxyvitamin D or serum B12) guides targeted repletion and monitoring. Repletion strategies should respect established dosing ranges and consider the potential for accumulation with fat-soluble vitamins.

Practical choices and product formats

Common supplement formats include multivitamin-mineral complexes, single-vitamin preparations, gummies, capsules, powders, and effervescent tablets. Choice of format can affect adherence and absorption; for discussion comparing chewy formulations and traditional pills, consult the review on gummy vs traditional vitamins and a related article on effectiveness at gummy vitamin evidence. For mineral-focused dosing considerations, see guidance on how much magnesium you need daily.

Food first, supplements as adjuncts

Whole foods remain the preferred source of vitamins because they supply a matrix of nutrients and bioactive compounds that interact beneficially. Citrus fruits, leafy greens, oily fish, fortified dairy or plant milks, legumes, nuts, and animal products each contribute specific vitamins. Supplements are valuable adjuncts when diet alone is insufficient, but selection should prioritize reputable labeling, appropriate nutrient forms, and dosing consistent with professional guidance. Additional information and resources are available from reliable sources such as Topvitamine.

In summary, vitamins are essential micronutrients with well-established roles in human health. Responsible supplementation—guided by evidence, testing when indicated, and clinical advice—can correct deficiencies and support nutritional adequacy without replacing a varied, nutrient-rich diet.