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Blindness increases the severity and mortality risk of infections RDA does not change after age 19, although ageing is associated with decreased clearance of vitamin A Yes^b Milk products, fish meat, some fruits and vegetables Milk products, grains, cereals MVMs, single Human diet has preformed vitamin A (retinol and its esterified form, retinyl esters, in animal source foods) and provitamin A carotenoids (beta‐carotene, alpha‐carotene and beta‐cryptoxanthin) Vitamin C (ascorbic acid) Synthesis of collagen, L‐carnitine, some neurotransmitters, protein metabolism, wound healing Severe deficiency known as scurvy RDA does not change after age 19; increased requirement for smokers Yes^a Fruits, vegetables, especially citrus fruits, tomatoes and tomato juice Some fruit drinks, some cereals MVMs, single, antioxidant complex Can be low in canned fruits and vegetables, as well as lost with prolonged cooking Vitamin D Bone mineralization, calcium and phosphorus homeostasis Muscle weakness, poor immune function and bone health (osteomalacia) RDA increased after age 70 in men and women Yes^{a, b} Highest in fatty fish; small amount in meat, cheese, egg yolks Fortified milk products, fluid milk, some yoghurts, some fruit drinks, some orange juice MVMs, single, with calcium Vitamin D3 (cholecalciferol) is preferred form as it is more bioavailable than vitamin D2 (ergocalciferol); high‐dose injections available under medical supervision, but lower daily doses may be preferable¹⁰ Vitamin E Antioxidant, immune function, cell signalling, regulation of gene expression, and other metabolic processes Rare; may occur with fat‐malabsorption with symptoms of peripheral neuropathy, ataxia, skeletal myopathy, retinopathy, poor immunity RDA does not increase after age 19 Yes^a Vegetable oils, nuts, seeds, whole grains, and green leafy vegetables Cereals MVMs, single, antioxidant complex Alpha‐tocopherol is considered the essential form; there are numerous other chemical forms Vitamin K Blood clotting (prothrombin), bone metabolism (osteocalcin) Clinically relevant when prothrombin time is increased AI does not increase after age 19 Green leafy vegetables Boost Plus MVMs at low levels in supplements formulated for older adults Phylloquinone is present primarily in green leafy vegetables and is the main dietary form of vitamin K; menaquinones produced by gut bacteria may satisfy some of the requirement for vitamin K Zinc More than 100 enzymes, protein, immunity, protein synthesis, wound healing, cell division Loss of appetite, impaired immunity, diarrhoea, eye and skin lesions, taste abnormalities RDA does not change after age 19 Meats, poultry, fish, milk products, and eggs Some cereals, grains MVMs, single Zinc is more bioavailable from animal‐sourced foods than from plants

      AI, adequate intake; MVM, multivitamin‐mineral supplement; RDA, recommended dietary allowance; UL, tolerable upper intake level; AI, RDA, and UL are terminology used in the US and Canada.³

      Source: Adapted from NASEM³; US National Institutes of Health, Office of Dietary Supplements⁵; USDA⁶; USDHHS, USDA⁷.

      ^a Considered nutrients of concern because of low intakes in the US.⁷

      ^b Considered nutrients of concern from systematic review and meta‐analysis in community‐dwelling older adults; vitamin D, thiamin, riboflavin, Ca, Mg, and Se.⁸

      Vitamin C is well known for being an antioxidant and is also needed for collagen formation.⁵ The severe vitamin C deficiency disease is known as scurvy, with symptoms of petechiae, ecchymoses, purpura, joint pain, poor wound healing, hyperkeratosis, swollen and bleeding gums, and tooth loss. Vitamin C also promotes iron absorption, especially the inorganic non‐heme forms of iron. Individuals who avoid fruits and vegetables and/or consume only the canned forms of fruits or vegetables are at risk for vitamin C deficiency. Vitamin C is present in most frozen and fresh vegetables but can be lost with prolonged cooking of fruits or vegetables, so steaming as a cooking method and shorter cooking times will optimize preservation of the vitamin.

      Nutrient antioxidants decrease oxidative stress by counteracting the adverse effects of reactive species, e.g. in the human body.¹² Although the most recognized antioxidant nutrients are vitamin C and vitamin E, many nutrients and other food‐derived compounds function as antioxidants.¹² Thus, dietary advice focuses first on eating a wide variety of foods with essential nutrients and other food components that have health benefits and less reliance on supplements of antioxidants.⁷ A healthy dietary pattern includes various fruits, vegetables, whole grains, calcium sources (e.g. dairy foods), and protein sources (e.g. animal‐sourced foods and/or plant foods high in protein, such as nuts and legumes).⁷

Role of vitamin and mineral supplements in chronic disease: some reviews of the evidence

      Even in industrialized countries, the vast majority of adults consume much less than the recommended amounts of many vitamins and minerals from foods, including magnesium, calcium, and vitamins A, C, D, E, and choline, as well as iron for young children, women of childbearing age, and women who are pregnant.^7,13 A systematic review of community‐dwelling older adults identified six nutrients that may be of public health concern: vitamin D, thiamin, riboflavin, calcium, magnesium, and selenium.⁸ Use of MVM supplements markedly improves nutrient intakes and decreases the risk of inadequate intakes.¹³

      While nutritional deficiencies and insufficiencies of any essential nutrients have health consequences, it is unclear whether routine supplementation of individual nutrients at or above the recommended amounts can prevent or treat chronic diseases that are not ‘deficiency’ diseases. While there is considerable interest in whether supplements of vitamins and/or minerals prevent or delay the progression of diseases, there has been insufficient research on the topic and conflicts in the evidence to date.^13,14 Longitudinal cohort studies typically examine the role of food intake patterns and/or dietary and supplemental sources of nutrients and chronic diseases. In these studies, it is often difficult to fully disentangle the effects of the supplements from other health‐seeking behaviours.¹⁴ Much of the information presented here is from randomized controlled trials (RCTs) in which participants are randomly assigned to one of several interventions with dietary supplements or a control group (placebo or no intervention). Across RCTs, there is variability in criteria used for disease outcomes and the amount and chemical form of the nutrient(s) in the supplements (see examples in Table

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