Micronutrients

Micronutrients are vitamins and minerals the body needs in small amounts.^{1Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 103.} They are needed in milligrams or less, compared with the grams of protein, carbohydrate and fat eaten as macronutrients.^{1Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 103.} Deficiencies can affect health, gym performance, hunger and muscle growth.^{1Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 103.} Minerals are inorganic; vitamins are organic.^{1Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 103.}

The water-soluble B vitamins and vitamin C aren’t stored in substantial amounts, except for B12; the body uses what it needs and excretes the rest.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 206.} Vitamins A, D, E and K are fat soluble and stored in fat tissue, making excess intake easier and deficiency slower to develop.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 208.},^{4Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 107.}

In practice

US dietary guidance lists fiber, potassium, calcium and vitamin D as nutrients of concern, and many women who can become pregnant are short of iron.^{5Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 197.} A calorie deficit raises the risk of falling short because less food provides fewer micronutrients.^{4Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 107.} Surveys of dieting bodybuilders most often found low vitamin D, calcium, zinc, magnesium and iron.^{6Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 108.}

Excess vitamins and minerals offer no benefit and can cause harm, with fortified shakes, bars, cereals and energy drinks increasing the chance of excess intake.^{7Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 133.} Too much preformed vitamin A, usually from supplements, is toxic.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 208.}

NSCA’s Essentials of Personal Training places supplement recommendations outside a personal trainer’s scope of practice and advises referral to a registered dietitian.^{8Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 134.}