Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 429

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 disease^35,36,37 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