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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See also Vitamin D Life

• Summary of Vitamin D trials - Grant Jan 2012
• Overview Evidence for vitamin D
• All items in category Meta-analysis 480 items
• All items in category Omega-3 330 items
• Vitamin D has a complex relationship with Cancer – meta-analysis July 2011
• Recent Vitamin D Meta-analysis and Reviews - July 2011
• Omega-3: many benefits include helping vitamin D