Update from the Cold Front

Content provided by the Faculty of the Harvard Medical School

There's no cure in sight, but there do seem to be ways to make the common cold less common.

Perhaps the only topic that rivals the weather forecast for idle chitchat this time of year is a rundown of cold symptoms. Was yours like a stalled pressure front that lingered for days, or did it come on as a nor'easter and knock you flat? But most of the time, we're fortunate. The typical cold is a relatively mild misery maker that goes away without special treatment after about a week.

Colds are caused by viruses that invade the upper respiratory tract (the mouth, nose, and trachea). Over 200 different viruses are capable of causing such an infection, which is perhaps one of the reasons colds are so common — and that a cure has been uncommonly difficult to find.

Because the infection is viral, not bacterial, antibiotics will not help the afflicted feel better. People do occasionally get a bacterial infection on top of the viral one, but that occurs only in a small number of cases. Dozens of over-the-counter cold medicines are available, but by design, they only relieve symptoms, and there are questions about how well they do that.

So the search goes on for anything that can fend off cold-causing viruses or speed their exit from your body. Here is a brief rundown of some of the candidates.

Vitamins. One of the first alternative methods to combat colds was promoted by Nobel laureate Linus Pauling in his 1970 book Vitamin C and the Common Cold. By and large, research hasn't supported Pauling's assertion that large daily doses — 1,000 to 2,000 milligrams (mg) — of vitamin C will prevent colds. Results from treatment studies have been similarly lackluster. The door is slightly ajar for strenuous exercisers, especially if they exercise in cold weather: some studies suggest that maybe they can prevent colds with vitamin C.

Researchers have found correlations between high vitamin D levels in the blood and fewer reported respiratory infections. One study showed a modest preventive effect from vitamin E among nursing home patients. But there isn't enough evidence to recommend either vitamin for cold-fighting purposes.

Echinacea. Prevention and treatment trials of echinacea haven't been very encouraging. A trusted review published several years ago arrived at a highly qualified conclusion that there's some (but not fully consistent) evidence that a preparation based on the aerial (above-ground) parts of Echinacea purpurea (there's more than one species of echinacea plant) might be an effective early treatment of colds in adults. In 2010, Consumerlab.com, a testing company, released the results of its review of 18 echinacea products. The company's tests couldn't determine whether the products contained the echinacea ingredients listed on the labels. Some minor consolation can be taken from none of the products exceeding the limits for heavy metal, chlorinated pesticide, or microbial contamination.

Many other botanicals have been offered up as cold preventives and cures — ginseng, elderberry, garlic, and olive leaf, to name just a few. But the research is limited, and none has emerged as clearly effective.

Zinc. Zinc's cold-fighting career got started with a 1984 report by a Texas researcher, George Eby, that claimed lozenges shortened colds by seven days. In between then and now, studies on zinc have been mixed. A 2011 metaanalysis that looked at 15 randomized trials of zinc lozenges or syrup versus placebo found that generally healthy people who took zinc within 24 hours of the onset of cold symptoms reduced the duration and severity of their cold, compared to people who took a placebo. That said, the researchers did find that people taking zinc in the form of lozenges reported nausea and a bad taste in their mouth. They also noted that further study is needed to tease out what dose and formulation of zinc is best.

Results from previous studies on a zinc gel were favorable, but the gels have also been linked to the loss of the sense of smell.

Exercise. Intense exercise weakens immunological defenses, at least temporarily, but moderate, regular physical activity may strengthen them. A study published in 2010 in the British Journal of Sports Medicine added to the evidence that a steady background of physical activity is protective. The study included 1,000 adults, ages 18 to 85, who filled out questionnaires for three months detailing their exercise habits and any cold symptoms. The study volunteers who exercised five days a week had 43% fewer respiratory symptoms than those who exercised one day a week or less.

Empathy. Researchers at the University of Wisconsin trained practitioners at two primary care clinics to exhibit differing levels of empathy with patients who came in for respiratory infections. Patients were asked to assess their interaction with the provider and return twice over the next 14 days to have their symptoms checked. According to results reported in the journal Family Medicine in 2009, the patients who ranked their providers highest for empathy on the first visit reported that their cold symptoms cleared up an average of a day sooner than the other study participants. Tests of nasal fluids showed that an empathic encounter also seemed to boost the immune system.

Sleep. Cold weather does not cause colds, nor do soggy socks or going out without a hat. But nagging parents may be right in one respect — getting a good night's sleep keeps you healthy and may keep colds away. University of Pittsburgh researchers recruited 150 healthy volunteers to keep a sleep diary for two weeks, and then enter a lab environment where they were exposed to a cold virus and watched for five days. The people who had reported less than seven hours of sleep a night were almost three times as likely to get infected as those who got eight or more hours of sleep.

Last Annual Review Date: 2/1/2011 12:00:00 AM

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More than 200 viruses can cause the common cold. There are more than 1 billion colds in the United States each year.