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 16.3). Thus, further research will continue to be needed to address these and other issues.
When available, this section emphasizes evidence from authoritative reviews and recommendations regarding the role of micronutrient supplements. The information comes from the US Preventive Services Task Force (USPSTF), Cochrane Reviews, meta‐analyses, and practice guidelines based on the best available information. Created in 1984, the US Preventive Services Task Force is an independent, volunteer panel of national experts in prevention and evidence‐based medicine. The Task Force works to improve the health of all Americans by making evidence‐based recommendations about clinical preventive services such as screenings, counselling services, and preventive medications. All recommendations are published on the Task Force’s website and/or in a peer‐reviewed journal.15 Cochrane Reviews are systematic reviews of primary research in human healthcare and health policy and are internationally recognized as among the highest standard of evidence‐based healthcare for prevention, treatment, and rehabilitation.16
To illustrate some of the better‐known relationships of specific antioxidant nutrients, vitamins, and minerals with selected diseases, conditions, and outcomes, several of those most relevant to older adults are summarized in the following sections. The chronic diseases and outcomes addressed include bone health and fracture risk, mild cognitive impairment and dementia, age‐related eye disorders, and cancer and cardiovascular disease, as well as the potential role of nutrient intake (focusing on zinc) in pressure ulcer injury healing. The section that discusses pressure ulcer injuries provides an example of a complex clinical condition in which malnutrition clearly plays a role but for which the causal relationships of specific nutrients are difficult to disentangle from the effects of other comorbidities and conditions. It also shows the challenge presented when a highly reliable biomarker for a given nutrient has not been identified, as is the case for zinc and several other micronutrients.
Bone health, fractures, vitamin D, and calcium
While not all osteoporotic fractures are directly attributable to deficiencies in vitamin D or calcium, these nutrients are essential for skeletal integrity and represent important modifiable factors associated with bone health.17 Vitamin D and calcium play a critical role in the prevention and treatment of osteopenia and osteoporosis. Along with other key determinants such as hormonal changes, these micronutrients must be present in adequate amounts for therapies with pharmacologic and nonpharmacologic treatments to be optimally effective. However, the potential benefits of these nutrients, which are very commonly under‐consumed from dietary sources, must be balanced with the potential risks of using supplemental forms.
Prevention of fractures in high‐risk populations
In a recent Cochrane Review, fracture outcomes were reported from 53 RCTs or quasi‐randomized trials of supplementation of vitamin D and/or calcium in postmenopausal women or men over age 65 from community, hospital, and nursing‐home settings and 22 trials of primarily participants with established osteoporosis in settings of institutional referral clinics or hospitals.17 Several forms of vitamin D were examined, including vitamins D2 and D3 (typically in foods and over‐the‐counter supplements) and activated forms of vitamin D (that are activated in the liver and/or kidney: calcidiol, alfacalcidol, and calcitriol). Vitamin D alone was not associated with preventing fractures, while vitamin D with additional calcium supplements reduced the risk of hip fractures and other fractures. Mortality risk was not increased from vitamin D and calcium supplements. However, an increased risk of other adverse effects was noted, such that it was recommended that those with kidney stones, kidney disease, high blood calcium, or gastrointestinal disease or those at risk of heart disease should seek medical advice before taking these supplements.18
Prevention of fractures in healthy populations
The use of supplements for primary prevention of osteoporosis‐related fractures in healthy populations lacks sufficient evidence to be recommended. An evidence review of 11 RCTs of vitamin D supplementation alone or with calcium found no association with reduced fracture incidence among community‐dwelling adults without known vitamin D deficiency, osteoporosis, or prior fracture (‘healthy populations’).17 With regard to potential risk of harm, supplementation with vitamin D alone, or in combination with calcium, did not increase all‐cause mortality, cardiovascular events, or cancer risk; and supplementation with calcium alone did not increase the incidence of kidney stones. However, supplementation with both vitamin D and calcium was associated with an increase in the incidence of kidney stones. USPSTF conclusions and recommendations in 2018 were as follows19:
The current evidence is insufficient to assess the balance of the benefits and harms of vitamin D and calcium supplementation, alone or combined, for the primary prevention of fractures in community‐dwelling, asymptomatic men and premenopausal women. (Insufficient ‘I’ statement.)
The current evidence is insufficient to assess the balance of the benefits and harms of daily supplementation with doses greater than 400 IU of vitamin D and greater than 1000 mg of calcium for the primary prevention of fractures in community‐dwelling, postmenopausal women. (Insufficient ‘I’ statement.)
Recommends against daily supplementation with 400 IU or less of vitamin D and 1000 mg or less of calcium for the primary prevention of fractures in community‐dwelling, postmenopausal women. (Discourage ‘D’ statement.)
These recommendations do not apply to people with a history of osteoporotic fractures of increased risk for falls, or a diagnosis of osteoporosis or vitamin D deficiency.
Summary
