Health Letter, February 2023
By Azza AbuDagga, M.H.A., Ph.D.
Minerals (such as calcium, magnesium, selenium and zinc) and vitamins (such as vitamins A, C, D, E and K and the B vitamins) are essential substances that our bodies need in certain small amounts to maintain life and overall well-being. Fortunately, healthy individuals can obtain enough of these nutrients by consuming a healthy, well-balanced diet that is high in fruits, vegetables, and other nutrient-dense foods.
Notably, one-half of American adults report a recent intake of at least one mineral, vitamin, multivitamin or herbal dietary supplement — which can come in several forms, including capsules, liquids, tablets and powders — likely as an “insurance” against possible nutrient gaps in their diet. These supplements also have been proposed as a prevention strategy for cardiovascular disease (such as heart attack and stroke) and cancer, the two leading causes of death in the U.S.
However, recent recommendations from the U.S. Preventive Services Task Force (USPSTF) — a volunteer panel of national experts in evidence-based medicine and disease prevention that works independently of industry influences — continue to refrain from endorsing the use of mineral, vitamin or multivitamin dietary supplements for this purpose.
The most recent USPSTF recommendation statement regarding this topic was published in the June 21, 2022, issue of the Journal of the American Medical Association.
The latest USPSTF recommendations
As a basis for its recommendations, the USPSTF commissioned a systematic review of the current evidence pertaining to the effects of using dietary supplements that contain minerals and vitamins as well as multivitamins for the prevention of cardiovascular disease, cancer or mortality. The population of interest for this review was adults aged 18 years or older who are not pregnant or trying to become pregnant; do not have known cardiovascular disease, chronic disease (other than hypertension, overweight or obesity) or nutritional deficiencies; and who live in the community (not hospitals or other health care settings).
Although the USPSTF identified 84 relevant randomized controlled trials and six cohort studies that met its criteria, it found the collective evidence pertaining to the use of many vitamin and mineral supplements to be limited. Nonetheless, this current evidence showed that most vitamin and mineral supplements provide no clinically important protective effects against cardiovascular disease, cancer or all-cause mortality in healthy adults without known nutritional deficiencies. Although there appears to be a slightly lower risk of cancer with multivitamin use, this finding was based on three limited trials. Notably, the USPSTF concluded that vitamin E had the strongest evidence, which showed a lack of benefit for this vitamin for preventing cardiovascular disease, cancer or all-cause mortality.
In terms of harm, the USPSTF found an increased risk of lung cancer with the use of beta carotene supplements, especially when they are used at the same time with vitamin A supplements, in persons who are at high risk of lung cancer (mainly smokers and those with a history of occupational exposure to asbestos). Other than that, the review found little evidence of serious harms associated with the use of most mineral and vitamin supplements. Nonetheless, the USPSTF cautioned that prior studies outside of its current review documented harm with using high doses of certain vitamins. For example, high doses of vitamin D supplements can increase the risk of high blood calcium levels and kidney stones. Additionally, whereas moderate doses of vitamin A supplements may reduce bone mineral density, high doses of this vitamin may be toxic to the liver or can cause congenital disorders in embryos or fetuses.
Upon balancing the net benefits and harms of vitamin and mineral supplementation, the USPSTF concluded with moderate certainty that the harms of beta carotene supplementation outweigh its benefits for the prevention of cardiovascular disease or cancer (see Table). It also concluded with moderate certainty that there is no net benefit for supplementation with vitamin E for the prevention of cardiovascular disease or cancer. Finally, for other single or paired nutrients as well as multivitamins, the evidence is insufficient to make a recommendation regarding their supplementation for the prevention of cardiovascular disease or cancer, according to the USPSTF. Notably, these recommendations were largely consistent with the USPSTF’s previous recommendations, which were issued in 2014.
Adults who are not pregnant or trying to become pregnant who live in the community
|Grade of Recommendation
|The USPSTF recommends against the use of beta carotene or vitamin E supplementation for the prevention of cardiovascular disease or cancer.
|There is moderate certainty that beta carotene or vitamin E supplementation has no net benefit or that the harms outweigh the benefits.
|The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the use of other single- or paired-nutrient supplements (other than beta carotene and vitamin E) for the prevention of cardiovascular disease or cancer.
|There is uncertainty about the balance of benefits and harms.
|The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements for the prevention of cardiovascular disease or cancer.
|There is uncertainty about the balance of benefits and harms.
Healthy nonpregnant adults without nutritional deficiencies do not need to take single or multiple mineral or vitamin supplements to prevent cardiovascular disease or cancer. Instead, they can effectively prevent cardiovascular disease and cancer by adopting healthy lifestyle habits. This includes increasing physical activity and eating a nutrient-dense diet (one that is high in fruits, vegetables, nuts, whole grains, fish and lean vegetable or animal protein), smoking cessation and stress reduction. Also, individuals who have diabetes, high blood pressure or high cholesterol should make sure these conditions are being appropriately controlled. For cancer prevention, healthy habits also include getting screened for common cancers and by addressing cancer-specific risk factors, as applicable.
Importantly, populations that are not covered in the USPSTF recommendation need to speak with their health care professionals regarding whether they need to take mineral, vitamin or multivitamin supplements. For example, all women who are planning or capable of pregnancy should take a daily supplement that contains 0.4 to 0.8 milligrams of folic acid to prevent neural tube defects in their babies. Additionally, individuals who have acute or chronic illnesses, including those with malabsorption conditions or dietary restrictions may need supplementation with certain nutrients.