New Article on Elderberry As Flu Medicine.

Elderberries are used in syrups, such as Sambucol. Getty Images

The Claim: The deep purple, almost black berries from the elder tree can shorten the duration of colds and flus, and help boost the immune system.

The Verdict: Elderberry extracts have antiviral activity in the laboratory and there is preliminary evidence that the berry—often consumed as a syrup or lozenge—can shorten the duration of flu symptoms. But further research is needed, scientists say, and there's scant evidence it eases the common cold or boosts the immune system. Among the elderberry products also found in stores: teas, capsules and oral drops.

Sambucus nigra, which grows in some parts of Europe, North America and Asia, is a flowering tree with berries that have long been used for cooking and medicinal purposes, scientists say. Elderberries have a strong flavor, similar to blackberries or cherries, and very little sweetness on their own, says New York naturalist and author Steve Brill, who likes them in muffins. Since they contain precursors to cyanide, it's important to cook them before eating, adds Mr. Brill. And steer clear of the leaves, which may be poisonous, he says.

In a review article published in January in the Journal of Dietary Supplements, scientists at Natural Standard Research Collaboration, which evaluates natural therapies, examined three human trials on elderberries. The trials involved a total of 151 patients taking syrups or lozenges.

The scientists gave the berry a grade of "B" denoting "good scientific evidence" for treatment of influenza, but more research is needed. Particularly needed is a comparison with modern flu medications, such as Tamiflu, says co-author Catherine Ulbricht, senior attending pharmacist at Massachusetts General Hospital in Boston and co-founder of Natural Standard, now owned by research and publishing firm Therapeutic Research Center Inc. in Stockton, Calif. To get Tamiflu, a doctor's prescription is required, and it can cause nausea and gastrointestinal side effects, doctors say.

Sambucol, which combats flu symptoms, can be taken on its own or as a topping. PharmaCare US

The elderberry formulation tested in two of the clinical studies reviewed by Natural Standard is sold as a syrup under the Sambucol brand. A four-ounce bottle, which costs about $13, contains a thousand elderberries and can be consumed plain or on ice cream or waffles, says Kimberly Weld, a vice president of PharmaCare US Inc., a San Diego unit of Australia's PharmaCare Laboratories Pty Ltd. that sells the syrup.

Missing from the scientific evidence is a clear understanding of how elderberry works, if it does, says Wendy J. Weber, a naturopathic doctor and epidemiologist at the National Center for Complementary and Alternative Medicine in Bethesda, Md. Studies have shown the elderberry's antiviral efficacy against a wide variety of respiratory-causing viruses in the laboratory but it's unclear if it kills viruses when ingested by mouth, she says.

In addition, elderberries contain anthocyanins, molecules some scientists think may boost the immune system, says Dr. Weber, but "there is a lot more research needed to determine whether [the berry] has a biological effect which could be of benefit."

If you do try elderberry, inform your doctor and don't skip a flu shot, the only proven way to prevent influenza, Dr. Weber says