Taking vitamin D has a slight impact on preventing colds and flu. In one analysis that included 37 randomized trials with 46,000 people, those who took vitamin D had an 8% lower chance of getting a cold or the flu than those who took a placebo.
If you catch a cold, know the facts. Studies have confirmed that taking vitamin C supplements regularly may only slightly reduce the duration and severity of symptoms. However, these supplements typically don't prevent you from catching a cold and can only slightly reduce the severity of symptoms for most people.
Starting vitamin C after symptoms doesn't seem to help much. However, consistent daily intake in large doses (1000-2000 mg) might shorten a cold by a day or so and make it milder. In more than 20 trials with nearly 11,000 participants, individuals who took 200 to 2,000 milligrams a day of vitamin C for an average of three months were no less likely to catch a cold than those taking a placebo. However, when they did catch a cold they were sick for slightly less time (about half a day less) than the placebo takers. A typical cold lasted about a week.
In seven separate studies, researchers tested vitamin C's ability to treat a cold. However, taking roughly 3,000 mg at the first sniffle didn't translate to a shorter or less severe cold. A few trials have tested whether vitamin C supplements can resolve Covid symptoms faster. Researchers randomly assigned 66 adults with mild-to-moderate Covid symptoms to take either a placebo or 1,000 mg a day of vitamin C for two weeks. Symptoms didn't clear up any faster in the vitamin C group than in the placebo group.
What about zinc?
A zinc deficiency can impair your immune system, so it's important to get enough zinc in your diet. Most people do. However, don't expect that taking a zinc supplement will help ward off a cold. In nine trials that included a total of 1,449 volunteers, taking zinc didn't lower the risk of getting a cold compared to taking a placebo. However, if you already have a cold, sucking on zinc lozenges, which slowly release zinc, may help you fight it off by preventing viruses from replicating or attaching to cells in your throat and nose.
In a few studies, adults who used zinc lozenges every few hours during a cold shortened their illness by roughly a third compared to those taking placebo lozenges. The studies, many of them funded by zinc supplement makers, required participants to take at least 75 milligrams of zinc acetate or zinc gluconate a day at the first sign of symptoms. Zinc lozenges containing citric acid, mannitol, sorbitol, or tartaric acid don't appear to have the same effect.
Vitamin D and the common cold
If you want to prevent a cold or flu, vitamin D might help a tiny bit. In one analysis that included 37 randomized trials with 46,000 people, those who took vitamin D had an 8% lower chance of getting a cold or the flu than those who took a placebo. While that finding was statistically significant, an 8% drop probably doesn't mean much for most people.
How about vitamin D for preventing Covid? Two huge trials (both were partly funded by vitamin companies) have investigated vitamin D supplements. In one study, researchers randomly assigned roughly 6,000 volunteers to daily doses of either 800 IU of vitamin D, 3,200 IU of vitamin D, or no supplement. After six months, vitamin D takers (regardless of dose) were no less likely to catch Covid (or any other respiratory infection) than the no-supplement group. The Recommended Dietary Allowance (RDA) for vitamin D is 600 IU a day up to age 70 and 800 IU a day for adults older than 70.
In a separate study, researchers randomly assigned 34,601 volunteers to take a placebo oil or cod liver oil (which contained 400 IU of vitamin D) every day for six months. The vitamin D made no difference. At the end of the study, 227 people in the cod liver oil group versus 228 people in the placebo group tested positive for Covid.
The common cold is an infection of your nose, sinuses, throat and windpipe. Colds spread easily, especially within homes, classrooms and workplaces. More than 200 different viruses can cause colds. There's no cure for a common cold, but it usually goes away within a week to 10 days. If you don't feel better in 10 days, it is recommended you see a healthcare provider.
Rhinoviruses cause up to 50% of common colds. There are more than 100 different rhinoviruses. However, other types of viruses such as coronaviruses can also cause colds. Antibiotics are medications that fight infections caused by bacteria. However, viruses cause colds and so antibiotics don't work for colds.
It can be hard to tell whether you have a cold or the flu since many of the symptoms are the same. Both are widespread during the colder months and affect your upper respiratory system.
Experts recommend drinking plenty of water. And get plenty of rest. It may be beneficial to run a humidifier or vaporizer to increase the amount of moisture in the air. Using saline nasal spray or drops and breathing in steam during a hot shower may significantly make a difference. Also, recommended are throat lozenges, cough drops, and taking over-the-counter medicines to relieve symptoms.
John Schieszer is an award-winning national journalist and radio and podcast broadcaster of The Medical Minute. He can be reached at medicalminutes@gmail.com
John Schieszer is an award-winning national journalist and radio and podcast broadcaster of The Medical Minute.
