Zinc is a “flu-fighter” that “keeps your immune system in working order,” AARP told its members last winter.
But taking zinc didn’t prevent colds or other respiratory infections in five studies that gave 10 mg to 20 mg of zinc—alone or as part of a multivitamin—or a placebo to some 2,560 mostly older adults every day for seven months to two years. (The DV for zinc is 15 mg.)
In a sixth trial, though, the 24 adults at a senior center in Detroit who were given 45 mg of zinc every day for a year were 67 percent less likely to get sick than the 25 adults who got a placebo.
Why the discrepancy? “Many of the elderly were zinc deficient,” says researcher Ananda Prasad of Wayne State University in Detroit. “We gave them more zinc and had them take it between meals to increase its absorption.” But Prasad’s study has yet to be repeated.
Zinc lozenges are more likely to help. In some studies, sucking on at least 75 mg of zinc from lozenges every day at the first sign of a cold cut its duration—though not its severity—by up to two days.
Sources: J. Am. Geriatr. Soc. 55: 35, 2007; BMJ 331: 324, 2005; JAMA 288: 715, 2002; Complement. Ther. Clin. Pract. 15: 91, 2009; Arch. Intern. Med. 159: 748, 1999; Am. J. Clin. Nutr. 85: 837, 2007; Cochrane Database Syst. Rev. 6: CD001364, 2013.
Other relevant links:
- Take the recommended amount of vitamin D but don’t rely on it to prevent colds. See: Vitamin D Fails to Stop Colds
- Taking high doses of vitamin C does not lessen your risk for colds or respiratory infections. See: Does Taking Vitamin C Protect You From Colds?
- Those taking multivitamins got sick just as much as those who did not. See: Can Multivitamins Prevent a Cold?