Q: Will vitamin C or zinc “immune boosters” really help my cold?
A: Many products are marketed to prevent and treat colds and other viral upper respiratory infections. These range from plain vitamin C to fancier powders you can mix with water and drink. Unfortunately, evidence that these products show actual benefits is lacking.
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Vitamin C is an important nutrient. Yet studies evaluating its effectiveness during acute illness show, at best, an 8% speedier recovery — meaning you’ll feel better 13 hours sooner during a typical seven-day illness. At worst, the studies demonstrate no benefit at all.
Some cold and flu prevention products contain zinc. While an old study on its use in treating colds was promising, the results were questioned because a zinc product manufacturer funded the research.
No studies on zinc have since shown any benefit. What’s more, toxicity from taking high amounts of zinc (beyond what you’d normally get in a multivitamin) is a definite risk.
It’s hard to know whether taking these cold products might produce a placebo effect or if any perceived benefit is due to hydration and electrolyte replacement.
— Family medicine physician Donald Ford, MD