medwireNews: The US Preventive Services Taskforce (USPSTF) continues to recommend against the use of beta carotene and vitamin E for the primary prevention of cancer or cardiovascular disease (CVD) in its updated 2022 recommendations, and maintains that the evidence is insufficient to assess the benefit–risk balance for the use of single- or paired-nutrient and multivitamin supplements.
“Although newer evidence was assessed, the USPSTF came to the same conclusions as it did in 2014, and the current recommendation statement is consistent with the 2014 recommendation,” the taskforce writes in JAMA.
The updated statement is based on a systematic review – conducted by Elizabeth O’Connor (Kaiser Permanente Northwest, Portland, Oregon, USA) and colleagues, and published in the same journal – that comprised 84 studies, including 52 published since the 2014 recommendations, evaluating vitamin and mineral supplementation for the prevention of cancer or CVD.
A pooled analysis of four randomized controlled trials (RCTs) with 94,830 participants showed that beta carotene supplementation with or without vitamin A was associated with a significantly increased risk for lung cancer, while an analysis of five RCTs with 94,506 participants showed an association with a significantly elevated CVD mortality risk. The respective odds ratios (ORs) for the analyses were 1.20 and 1.10.
With regard to vitamin E supplementation, the study authors found “no benefit for mortality, cardiovascular disease, or cancer” in the nine (n=107,772 participants), four (n=62,136), and five (n=76,777) trials, respectively, that addressed this issue. But two of the four studies reporting on hemorrhagic stroke showed a significantly increased risk for the outcome and associated mortality among vitamin E users.
The taskforce therefore “concludes with moderate certainty that there is no net benefit of supplementation with vitamin E” in the preventive setting.
The systematic review demonstrated a significantly lower risk for cancer with the use of multivitamins (OR=0.93), but this finding was based on four RCTs (n=48,859), of which only three were adequately powered, one had a median of just 3.6 years of multivitamin use, and one was limited to antioxidants, caution O’Connor and co-authors.
This led the USPSTF to conclude “that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements,” a conclusion that was also applied to the use of single- or paired-nutrient supplements based on the available evidence.
The USPSTF stresses that these recommendations apply to “community-dwelling, nonpregnant adults,” and not to “children, persons who are pregnant or may become pregnant, or persons who are chronically ill, are hospitalized, or have a known nutritional deficiency.”
The authors of an accompanying editorial note that “[i]n 2021, people in the US spent an estimated almost $50 billion on dietary supplements and the dietary supplement industry spent about $900 million on marketing.”
They believe that “[b]eyond wasted money, the focus on supplements might be viewed as a potentially harmful distraction.”
Jeffrey Linder and co-authors, from the Northwestern University Feinberg School of Medicine in Chicago, Illinois, USA, write: “Rather than focusing money, time, and attention on supplements, it would be better to emphasize lower-risk, higher-benefit activities.”
They continue: “Health systems and health care professionals should focus on evidence-based preventive services recommended by the USPSTF, including controlling high blood pressure and behavioral counseling to encourage physical activity and a healthy diet.”
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