Flu-fighting supplements

But the more effective ones aren't being used, our poll finds

Last updated: November 2010

A "try everything" approach to fighting the flu seems to be common among nearly half of Americans, who said they plan to use nutritional supplements or homeopathic remedies to protect themselves from the flu this season or fend off its symptoms.

According to a nationally representative poll of 1,500 adults by the Consumer Reports National Research Center conducted in September, these supplement users are as likely as nonsupplement users to have definite plans to get a flu shot. More than one-third of supplement users planned on getting the flu vaccine, and 62 percent planned to use prescription or over-the-counter treatments, or both, to protect themselves against the flu. Only 13 percent said they plan to use supplements and none of the conventional medical treatments mentioned above.

Supplement users also hedge their bets by taking, on average, four different kinds of supplements as flu remedies. However, the supplements with the best (though still preliminary) evidence for efficacy in fighting off the flu–including elderberry and n-acetyl cysteine–are not top of mind among supplement takers. Vitamin C and multivitamins were the supplements cited by about 40 percent of Americans, with the next most popular being zinc (22 percent), combination herbs (17 percent), garlic (17 percent), and homeopathic flu remedies (13 percent).

Women were more likely than men to say they would use supplements to fight the flu, and people from 45 to 64 years old were more likely than those younger or older to say they would take supplements to protect against the flu, according to the CR poll.

Which supplements work against flu?

Our survey asked specifically about 13 types of dietary supplements and allowed respondents to list any others they used as flu remedies. Just 9 percent of those surveyed said they planned to try elderberry or n-acetyl cysteine this winter, two supplements that, as of November 2010, were rated "possibly effective" against flu symptoms. Our analysis of supplements was based on information from the Natural Medicines Comprehensive Database (NMCD), a compendium from an independent research group that evaluates the evidence for safety and effectiveness of nutritional supplements. Both elderberry and n-acetyl cysteine are available as single ingredient supplements or as part of multi-ingredient formulations.

Clinical research suggests that some elderberry extracts might help relieve flulike symptoms within 2 to 4 days of treatment for most patients. Supplements of n-acetyl cysteine, an amino acid derivative that's also available as a prescription drug for lung problems due to pneumonia and other causes, might also help reduce flu symptoms. An Italian clinical trial published in 1997 of 262 mostly elderly people found that those who received the supplement during winter (the height of flu season) had significantly fewer flu infections and milder symptoms than those given the placebo.

It's unclear whether the people surveyed chose those supplements because they knew there was some evidence of efficacy. What raises doubts is that elderberry and n-acetyl cysteine users said they planned to take a total of eight types of supplements as flu remedies, about twice the average number most supplement users planned to take this flu season, our survey found. Cost isn't the only downside to a "might as well take them all" approach to supplement taking: Supplements have side effects and may interact with prescription and over-the-counter medications.

NMCD rates n-acetyl cysteine supplements as "likely safe," and elderberry extracts as "possibly safe" for short-term use, but it's important to first check with your doctor or pharmacist. Most supplements haven't been studied in pregnant or nursing women, who should avoid them. Elderberry plants and fruit contain a cyanide-producing chemical. Consuming the plant's leaves, flowers, or unripened or uncooked fruit can result in nausea, vomiting, and diarrhea. Ingestion of large quantities may cause serious toxicity. People with allergies to grass pollen should also avoid elderberry extracts because of the potential for an allergic reaction.

Other supplements used as flu remedies, such as vitamin C and zinc, have been found to be possibly effective against the common cold, according to the NMCD, but not against the flu. While preliminary evidence published in 1997 suggested that zinc with selenium might fight flu infections in older, institutionalized patients, the evidence was weak, and the NMCD has rated zinc supplements as "possibly ineffective" against influenza.

The survey did not ask specifically about vitamin D supplements, but in a randomized clinical trial involving 334 Japanese school children, published in the May 2010 American Journal of Clinical Nutrition, children who took vitamin D supplements had a significantly decreased chance of contracting influenza A. Only 18 of the 167 children taking vitamin D3 supplements got influenza A, compared with 31 of 167 children in the placebo group. There was, however, no significant difference between the two groups in catching influenza B. Children who had not previously taken vitamin D supplements showed the most benefit in this trial, suggesting that they might have been vitamin D deficient.

The NMCD concluded that vitamin D supplements are "possibly effective" in reducing the chance of catching the flu, and "likely safe" when used appropriately.

Children and adults with severe flu symptoms—including severe diarrhea, vomiting, difficulty breathing, and high fevers—should seek medical attention and not just rely on supplements.

Supplements plus mainstream medicine

Skepticism about flu vaccines does not seem to be the main motivating factor in people who planned to use supplements or homeopathic drugs, our survey suggests. As noted previously, 35 percent of that group said they definitely planned to get a flu vaccination this season. However, respondents who were undecided about the flu shot were significantly more likely than definite flu shot recipients to use supplements. Those supplement users who were undecided about getting the flu shot seemed to be actively considering that decision and were open to the advice of medical experts. Interestingly, undecided supplement users were much more likely to be influenced by their health-care providers (81 percent vs. 67 percent) than undecided Americans who had no plans to take supplements. Supplement takers were also more likely to say that advice from both family and friends would influence their to-be-made flu shot decision.

The Centers for Disease Control and Prevention recommends that all people 6 months and older get this season's vaccine. The flu vaccine has proved to be safe over many decades, according to our medical advisers. While estimates vary, overall the vaccine has been found to reduce flu episodes by about 70 to 90 percent in healthy adults. It's less effective in older people and those with compromised immune systems, but it can also lessen the severity of the flu, limiting the possibility of serious complications and deaths.

Also consider these other steps, which have been shown to reduce the risk of getting the flu:

  • Wash your hands. Use disinfectant wipes on telephone and computer keyboards to prevent the transfer of viruses.
  • Avoid close contact with sick people. And stay home if you have a cough and fever. Cover coughs and sneezes with tissues or the crook of your arm.
  • Get plenty of sleep. Sleep-deprived volunteers in one study mustered half the immune response to a flu shot compared with those getting normal sleep. Eating well, exercising regularly, and reducing stress may also bolster immunity.
  • If you smoke, quit. Smokers are vulnerable to the flu and its complications.

This survey and report were made possible by a grant from the Airborne Cy Pres Fund, which was established through a legal settlement of a national class-action lawsuit (Wilson v. Airborne Health, Inc., et al.) regarding deceptive advertising practices.

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