Supplementation

Over 70% of Americans take some form of dietary supplement every day, and the supplement industry is currently big business with a gross of over $28 billion. ^[1] Unlike either foods or drugs, supplements do not need to be registered or approved by the US Food and Drug Administration prior to production or sales, and under the Dietary Supplement Health and Education Act of 1994 the FDA is restricted to adverse-report monitoring postmarketing. ^[1] It is proposed that nutrients required for the function of longevity proteins constitute a class of vitamins named longevity vitamins, whose deficiency triggers a rationing mechanism that favors survival proteins while sacrificing proteins that protect against future damage. ^[2]

As proposed by the triage theory, a modest deficiency of one nutrient or cofactor triggers a built-in rationing mechanism, and impairment of the function of longevity proteins results in an insidious acceleration of the risk of diseases associated with aging. ^[2] Dietary protein supplementation significantly enhances changes in muscle strength and size during prolonged resistance exercise training in healthy adults, though protein intakes greater than about 1.62 g/kg/day do not further contribute to gains in fat-free mass. ^[3] Creatine supplementation in conjunction with resistance training augments gains in lean tissue mass and strength in aging adults. ^[4]

Despite widespread consumption, there is limited evidence of health benefits related to nutraceutical or supplement use in well-nourished adults, while a small number of these products have the potential to produce significant toxicity. ^[1] An Endocrine Society guideline suggests empiric vitamin D supplementation for children and adolescents aged 1 to 18 years, adults over 75 years, those who are pregnant, and those with high-risk prediabetes, but suggests against empiric supplementation above the current dietary reference intakes to lower disease risk in healthy adults younger than 75 years. ^[5] The same guideline found no clinical trial evidence to support routine screening for 25-hydroxyvitamin D in the general population and suggests against routine testing in all populations considered. ^[5] In frailty guidelines, protein or caloric supplementation is recommended when weight loss or undernutrition are present, whereas no recommendation was given for systematic additional therapies such as vitamin D supplementation. ^[6]

Because nutrient deficiencies are highly prevalent in the United States and elsewhere, appropriate supplementation and/or an improved diet could reduce much of the consequent risk of chronic disease and premature aging. ^[2] Patients often do not disclose supplement use to their physicians, so the risk of adverse drug-supplement interactions is significant. ^[1] Malnutrition in older adults, including hidden micronutrient deficiencies that are frequently overlooked, may in some cases require targeted supplementation of macronutrients and/or micronutrients when diet alone is not sufficient to meet age-specific requirements. ^[7]