• Product: Halls ProHealth Defense dietary supplement, $4.99 for 18 drops, at CVS, Walgreens, Wal-Mart.

• Key ingredients: Vitamins A, C and E, zinc and extract of rose hips, echinacea purpurea, American ginseng, chamomile, green tea extract and astragalus.

• The pitch: Strengthens your immune system, helps prevent colds.

• Pros: Zinc may support healthy immune function and increase activation of T cells responsible for destroying viruses and bacteria, suggests a University of Florida study in the August 2009 issue of the Journal of Leukocyte Biology. A meta-analysis of 14 studies found that echinacea decreased the odds of developing the common cold by 58 percent and the duration of a cold by 1.4 days, according to a report in The Lancet in July 2007. Some ginseng extracts could have anti-inflammatory effects, although further research is needed, according to a University of Hong Kong report in the May 2009 Journal of Translational Medicine. Although most research today does not back up his claim, Nobel Prize winner Linus Pauling wrote in his 1970 book, ``Vitamin C and the Common Cold,'' that taking 1,000 milligrams of vitamin C daily would reduce the incidence of colds by 45 percent for most people.

• Cons: A July 2007 review of vitamin C research concluded that most people cannot prevent the common cold by taking vitamin C (although it might reduce the duration of the cold), according to the Cochrane Database of Systematic Review. A University of Pittsburgh Medical Center report rejects echinacea, vitamin C and zinc as treatments for colds. This product shouldn't be used more than eight weeks; overdosing on vitamin C can cause kidney stones.

• Bottom line: The best way to avoid a cold is still to regularly wash hands and avoid touching the face. Getting enough sleep helps, too. A study in the Jan. 12, 2009, issue of Archives of Internal Medicine found that people who get less than seven hours of sleep appear about three times as likely to develop respiratory illness if exposed to a cold virus, compared to those who sleep eight hours or more.

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