and cardiovascular diseases – selenium
Selenium has been identified as a nutrient of concern in community‐dwelling older adults.8 According to a Cochrane Review, because of the use of selenium in enriched foods, supplements, and fertilizers in some countries, there could be an increased perception that selenium reduces the risk of cardiovascular disease and other chronic diseases.30 However, the results of studies to date are equivocal. Based on the results of 12 RCTs that provided selenium supplements to adults considered primarily healthy and well‐nourished, it was concluded that selenium supplements did not influence all‐cause mortality, CVD mortality, non‐fatal CVD events, or all CVD events (fatal and non‐fatal). In agreement with other studies, adverse events associated with selenium supplementation included alopecia and dermatitis.
Cai et al.31 examined relationships of selenium and cancer from RCT, cohort, or case‐control studies that included selenium as baseline exposure and outcomes as cancer events (incidence and mortality). Sixty‐nine studies were identified that were assessed through meta‐analysis, meta‐regression, and dose‐response analyses. Overall, high serum/plasma or toenail selenium had some efficacy for cancer prevention, such that higher selenium exposure decreased the risk of breast cancer, lung cancer, oesophagal cancer, gastric cancer, and prostate cancer but not colorectal cancer, bladder cancer, or skin cancer.31 In contrast to this finding, Vincenti et al.32 conducted meta‐analyses of RCT and cohort studies of selenium in a Cochrane Review and found that the higher quality RCTs showed no benefit for selenium supplements in reducing the risk of cancer. Unexpectedly, some RCTs suggested that selenium supplementation may increase the risks of high‐grade prostate cancer and type 2 diabetes.32
Based on the contradictory nature of the evidence, supplementation with selenium to reduce the risk of cancer or cardiovascular diseases does not appear warranted at this time. In the next section, comprehensive meta‐analyses of several vitamins and minerals, alone or in combination, are reviewed for their health benefits and risks regarding cardiovascular disease and cancer.
Cancer and cardiovascular diseases – multiple vitamins and minerals
Cancer and cardiovascular diseases are leading causes of mortality worldwide, and there is interest in whether micronutrients provide primary or secondary prevention against these diseases. The USPSTF has many recommendations on preventing cardiovascular disease and cancer, including smoking cessation; screening for lipid disorders, hypertension, diabetes, and cancer; obesity screening and counselling; and aspirin use.15 Given the many important functions 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
