Does Zinc Really Help Cure the Common Cold?

Pharmaceutical companies have added zinc to some cold remedies for years, but medical opinion has gone back and forth on whether it helps.

Zinc is a useful metal in industry, and of course skiers and others who spend a lot of time outdoors have been using zinc-based sunblock for ages. (That's why pro skiers always have white smears on their noses whenever you see them on TV).

Zinc compounds are also popular in over-the-counter remedies for the common cold. Doctors have been on the fence about whether zinc actually eases colds or not, but as of mid-June 2011, it's mostly getting the thumbs up -- in certain circumstances.

An Iffy Benefit

One of the reasons the medical establishment hasn't been keen on the zinc/cold connection is because no one can figure out quite how it would works. Zinc may deactivate cold viruses somehow, or simply keep them from sticking to nasal membranes.
Now, you do need trace amounts of zinc for certain bodily functions: cell growth, wound healing, immune system support, and keenness of both smell and taste. But too much zinc can be bad for you.

Downside

Excess zinc blocks the absorption of copper, another essential trace element. It can also depress the immune system, interfere with the formation of blood cells, and cause cramps, mouth sores, diarrhea, and vomiting.
In addition, if applied to the nose, zinc can cause anosmia: the loss of the sense of smell. This is one of the reasons why the FDA cracked down on nasal swabs and gels containing zinc in 2009.
All it takes to cause any of these problems is as little as 50-75 milligrams a day for long periods. Recommended daily doses are 8-11 mg for adults, and 3-8 mg for kids under 13.

However...

In 2011, a re-analysis of 15 studies from 1987 on revealed that some zinc-based OTC products really can reduce a cold's severity and shorten it by up to a day, assuming you start taking the products within 24 hours of the onset of symptoms. Typical doses are 30-190 mg.
Lozenges work best, with those containing zinc acetate being most effective. Zinc gluconate seems to work, too. Just don't take too many over a long period of time. Now, you'd think this wouldn't be a problem, since zinc has a nasty aftertaste.

Beware

The remedy-makers are well aware of the aftertaste, which is why they add things like ascorbic acid, sorbitol, and citric acid to mask it. Unfortunately, such substances may keep the zinc from working at all. Check the ingredients list before you buy, and move on if a remedy contains the above.
Apparently, cold remedies containing zinc really can help you beat a cold if you act immediately -- but you'll have to put up with a strong aftertaste for that to happen, at least for now.