The common cold is an infection caused by many different viruses. A recent analysis of randomized, placebo-controlled trials published in the British Journal of Clinical Pharmacology showed that zinc acetate lozenges may reduce the duration of the common cold by nearly three days.
The effect of zinc lozenges was not changed by allergy status, smoking, symptom severity, age, sex or ethnic group. High-dose lozenges shortened the duration of symptoms of nasal discharge by 34 percent, of nasal congestion by 37 percent, of scratchy throat by 33 percent, of cough by 46 percent and of muscle aching by 54 percent. There was no evidence of an effect on headache or fever symptoms.
Because high doses of zinc can cause side effects such as nausea, dosages should not exceed 100 mg per day. Most zinc acetate lozenges contain 18.75 mg of zinc, and for most people, taking two daily is helpful. Simply taking supplemental zinc in pill form may not have the same effects, because it is the zinc dissolved in saliva that is believed to be effective.
According to an updated review of vitamin C and the common cold, vitamin C halved the incidence of contracting the common cold among people undergoing physical stress, such as marathon runners, or people working in the cold. Vitamin C may also reduce bronchoconstriction (asthma-like symptoms) caused by exercise. Some, but not all studies, indicate that taking vitamin C shortens the duration of a cold.
A recent report from the University of Colorado School of Medicine looked at the use of vitamin D among older, long-term care residents of nursing homes. There was a 40 percent reduction in acute respiratory illness among those who were given 100,000 international units of vitamin D a month (averaging 3,300 IU to 4,300 IU daily) compared to those receiving 12,000 IU per month (averaging 400-1000 units daily). There were more falls, although not more fractures, in patients receiving the higher doses, however. Further studies will look at giving patients a daily dose of vitamin D rather than very high dosages monthly.
Numerous other studies of vitamin D have shown that supplements lowered the incidence of respiratory infections in children and adults. Most studies have shown that a blood level of at least 30 nanogram/millilitre of vitamin D is desirable. Check with your primary care provider for a test of your vitamin D blood level.
In the meantime, taking a vitamin D supplement of 1,000 IU is probably safe and desirable for most people, especially in the winter months when sun exposure is minimal at our latitude. Have some zinc acetate lozenges on hand and keep up your vitamin C intake with citrus and other raw fruits and vegetables, or take a supplement.
Consider taking a probiotic supplement as well. A study from the University of Medicine and Dentistry in New Jersey showed that students taking a probiotic supplement had a shorter duration of colds and symptoms that were 34 percent less severe. Include fermented foods such as yogurt in your daily diet as well.
Finally, if you haven’t had a flu shot this year, it’s still not too late. Go for it!
Sadja Greenwood is a Bolinas resident and retired physician formerly active at the University of California, San Francisco.