of micronutrients, it is intriguing to explore whether their intake and/or status could be another important modifiable risk factor for these diseases. However, research on vitamin and mineral supplements is challenging, given the numerous types of cancer and cardiovascular diseases and the many nutrients that may be involved in these complex disease processes.
The USPSTF’s recommendations regarding vitamin and mineral supplements for primary prevention of cancer and cardiovascular disease were published in 2014 and are currently undergoing revision.15 This section is based on the evidence review33 and the USPSTF’s clinical recommendations.34 Researchers reviewed 103 articles based on 26 unique studies, which is considered a low number given the complexity of these diseases. There were considerable variations in study populations, e.g. men only or men and women, as well as in the formulations of supplements (single, several, or up to 30 nutrients in some MVMs). Overall, the majority of studies showed no effect of micronutrient supplements in healthy populations, and the heterogeneity of the studies limits generalizability to the general primary care population. Beta‐carotene showed an increased risk of lung cancer incidence and mortality among individuals at high risk for lung cancer at baseline (smokers and asbestos‐exposed workers); this effect persisted even when combined with vitamin A or E. In 2014, the USPSTF made recommendations that apply to healthy adults without special nutritional needs; the recommendations do not apply to children, women who are pregnant or may become pregnant, or people who are chronically ill or hospitalized or have a known nutritional deficiency.34 The USPSTF’s conclusions in 2014 were based on evidence that was considered insufficient or inadequate, and their clinical summary included the following34:
Preventive medication: Evidence on supplementation with multivitamins to reduce the risk for cardiovascular disease or cancer is inadequate, as is the evidence on supplementation with individual vitamins, minerals, or functional pairs. Supplementation with beta‐carotene or vitamin E does not reduce the risk for cardiovascular disease or cancer.
Balance of benefits and harms:The evidence is insufficient to determine the balance of benefits and harms of supplementation with multivitamins or single or paired nutrients for the prevention of cardiovascular disease or cancer.There is no net benefit of supplementation with vitamin E or beta‐carotene for the prevention of cardiovascular disease or cancer.Beta‐carotene or vitamin E is not recommended for the prevention of cardiovascular disease or cancer. (Grade ‘D’, and use is discouraged.)
Meta‐analyses including RCTs published since 2014 also do not support benefits of multinutrient or single supplements in primary prevention of cardiovascular disease35,36,37 or cancer.37 The authors of a large systematic review and meta‐analysis of 49 primary prevention trials concluded that dietary supplements do not prevent cancer and cardiovascular diseases or reduce the risk of mortality. There are a few exceptions to this general finding, and it is important that they be interpreted carefully within the context of the overall findings.37 For example, supplementation with vitamin E may reduce the risk of cardiovascular mortality, and folic acid supplements may decrease the risk of cardiovascular diseases, while calcium supplements may reduce the risk of cancer.37 In agreement with previous research, beta‐carotene provided as a single nutrient or in high doses (30 or more mg daily) and vitamin A (25,000 IU or more daily) were associated with an increased risk of all‐cause mortality and cancer mortality.37
Practical implications
Given the limited support for the efficacy of micronutrient supplements in preventing disease and the potential concerns about adverse effects, it is essential to read labels and select supplements that contain equal to or less than the recommended amounts of specific nutrients (e.g. 100% of recommendations for general health), which are well below the amounts of concern for beta‐carotene and vitamin A. Even the potential benefits of vitamin E are within the range in MVM supplements (100–150% of recommendations for general health). The potential benefits (and risks) of folic acid supplementation might not be seen with typical MVM supplements, and clinical trials of folic acid are often investigated in combination with other nutrients (vitamin B6 and vitamin B12). Additional research is needed to confirm the beneficial effects observed for vitamin E, folic acid, and calcium supplements in recent meta‐analyses.37
Nutrient intake and healing of pressure injury: focus on zinc
A nutritional concern especially relevant for older adults in long‐term care facilities and frail older adults being cared for at home is pressure ulcer prevention and treatment. The prevalence of pressure ulcers is not well known but has been reported to be as high as 30% in long‐term care and 19% in home‐care patients38; and while derived from a varied aetiology, the condition is well known to have a strong malnutrition component. Factors such as repositioning, mattress selection, and wound care also represent key aspects of treatment, but there is no question that a shortage of protein, calories, or/other nutrients required for wound healing would hamper recovery from pressure injury.38
The current state of science on pressure ulcer treatment is equivocal on specifics, but it is widely accepted in clinical practice that nutritional repletion with an oral nutrition supplement (ONS) can benefit malnourished patients with pressure injuries.38,39 ONSs contain nearly all essential nutrients, including vitamins and minerals. A 2014 Cochrane Review40 examined the results of 14 RCTs evaluating the effects of enteral or parenteral nutrition on the prevention and treatment of pressure ulcers. The trials were heterogeneous with regard to participants, interventions, nutrients used in the interventions, comparisons, and outcomes, and the review found no clear evidence of an improvement in pressure ulcer healing from the nutritional supplements.
A more recent review by Heintschel and Heuberger38 considered 10 studies of ONS, including both standard and speciality formulas. The review focused specifically on zinc, based on the role of this essential mineral in a number of anabolic processes including DNA repair and protein metabolism as well as several aspects of immunocompetence. Zinc intakes tend to be low in older adults, but there is a lack of reliable biomarkers of zinc status. While the authors concluded that both standard and speciality ONS improved outcomes, it was not possible to distinguish a preferable formulation. The authors also noted the unreliability of zinc biomarkers and the lack of a significant response of pressure injury to zinc sulfate administration as factors that furthered hampered understanding of the potential impact of zinc status. Thus, while the role of ONS in the prevention and treatment of pressure ulcers was confirmed, the precise role of micronutrients such as zinc await confirmation through further studies in higher quality and more consistent RCTs.
Summary
Vitamins and minerals perform essential metabolic and physiologic functions in the body, can be obtained from a wide variety of foods, and also can be consumed as supplements when insufficiently supplied from diet alone or when therapeutic doses are needed. Frank micronutrient deficiencies produce classic deficiency syndromes and clearly should be treated. Marginally deficient intakes over time can also lead to suboptimal outcomes in a variety of systems and should be corrected. Users of supplements of vitamins and minerals, such as MVMs, are less likely than nonusers to be deficient in several micronutrients.13 Along with a healthy dietary pattern, a daily MVM may be a practical way to compensate for shortfalls in micronutrient intakes.4,13 Supplements of various vitamins and minerals generally have not been beneficial in primary prevention of chronic diseases. The development and progression of chronic diseases occur over decades, so it is unlikely that a few years of supplementation in late life will prevent diseases such as cancer and cardiovascular diseases.
Key points
Age‐associated changes in food intake, such as social factors, psychological problems, physiological decrements, chronic disease, polypharmacy, and medical factors, contribute to protein‐calorie inadequacies and deficiencies of micronutrients.
Single and/or MVM preparations are frequently consumed by older adults, and