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Vitamin D and omega-3 are the only supplements which show benefit in meta-analysis – Jan 2012

Do Dietary Supplements Have Beneficial Health Effects in Industrialized Nations: What Is the Evidence?

JPEN J Parenter Enteral Nutr. 2012 Jan 24.
Marik PE, Flemmer M., Eastern Virginia Medical School.

BACKGROUND: Dietary supplements are regularly used by at least half of the American population, yet the health benefits of these agents are unclear.

OBJECTIVE: A systematic review to determine the benefits and risks of dietary supplements in Westernized societies. Data Sources: MEDLINE, Embase, Cochrane Register of Controlled Trials and citation review of relevant articles. Study Selection: Randomized, placebo-controlled clinical trials in non-pregnant Westernized adults that evaluated clinical outcomes of nutritional supplements. Data Extraction: Data were abstracted on study design, study size, study setting, patient population, dietary intervention and clinical outcomes. The outcome of each study was classified as non-beneficial, beneficial or harmful according to whether the end-point(s) of interest reached statistical significance.

Data Synthesis: Sixty-three studies met the criteria for our systematic review.

  • No benefit was recorded in 45 studies, with
  • 10 of these showing a trend towards harm and with
  • two showing a trend towards benefit.

Four studies reported harm with increased cancer deaths (n=2) and increased fractures (n=2). Two studies reported both a harmful as well as a beneficial outcome.
A beneficial outcome

  • was reported in 12 studies;
  • 6 which studied vitamin D and
  • three which investigated omega-3 fatty acids.

While a benefit was reported in one study each which investigated

  • Vitamin E,
  • folic acid and
  • Ginkgo biloba

this benefit was not confirmed by larger and more adequately powered studies.

CONCLUSIONS: With the possible exceptions of Vitamin D and omega-3 fatty acids there is no data to support the widespread use of dietary supplements in Westernized populations; indeed, many of these supplements may be harmful. (JPEN J Parenter Enteral Nutr. XXXX;xx:xx-xx).

PMID: 22275325
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