Dear Readers,

It is estimated that the common cold is responsible for 150 million missed workdays each year in the United States. With cold and flu season fast-approaching, many of us will be headed to the nutrition supplement aisle in an attempt to ward off these nasty viruses. But do these supplements really work? We investigated four of them, and this is what we found:

• Elderberry — In one small study, elderberry syrup given four times daily was found to improve symptoms of influenza four days faster than placebo. In another study of 312 air travelers, those using elderberry had an average of a 2-day shorter duration of the cold and also experienced fewer symptoms. Larger studies need to be performed in order to confirm these results. Remember, it takes several studies before scientific value can be determined.

• Vitamin C — In a meta-analysis involving more than 11,000 participants, 200 mg of vitamin C daily did not reduce the risk of getting a cold for the general population. However, the same dosage did reduce the length of the illness by about one day. In order to obtain this benefit, the supplement must be taken every day, not only when you realize you are getting a cold.

• Zinc — In a review on zinc and the common cold, researchers Meenu Singh and Rashmi R. Das found that taking zinc within 24 hours of symptom onset, the illness was reduced by about one day, and the severity of symptoms was also reduced. It is important to note that excessive amounts of zinc can cause copper deficiency, anemia and damage to the nervous system. Also, in 2014 the FDA warned against the use of zinc nasal sprays due to permanent loss of smell in more than one hundred people. The tolerable upper limit of zinc is 40 mg per day for adults, less for those under the age of 18.

• Echinacea — While echinacea has been shown to stimulate the production of immune cells, studies are mixed when it comes to preventing the common cold and the severity of its symptoms. Overall, some estimate it may reduce your chances of getting a cold by 10-20 percent.

Given the modest effect of dietary supplements on the prevention of the common cold, the best defense may be good old-fashioned self-care: Eat right; get plenty of sleep; exercise regularly and wash your hands frequently.

Until next time, be healthy!

Dear Dietitian

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Leanne McCrate, RD, LD, CNC,

aka Dear Dietitian, is an award-winning dietitian based in Missouri.