At the first signs of a cold, many of us pour a big glass of OJ on the assumption that loading up on vitamin C is a surefire way to kick just about any bug.
Some nose-blowers may also reach for “immunity boosters” like Airborne and Emergen-C to cure the sniffles. But does vitamin C — and the supplements that tout its benefits — really work to prevent (or cure) the common cold?
Researchers have studied the role that vitamin C, aka ascorbic acid, plays in preventing and treating the common cold for more than 70 years. And spoiler: We still don’t quite know all the facts.
A 2013 research review concluded that supplementing your diet with 200 milligrams or more of vitamin C has no impact on the risk of getting a cold. But it does have the potential to shorten the duration of an existing cold and reduce its severity.
Research showed that taking 1 to 8 grams of extra vitamin C per day may lighten your sniffles. A 2006 research review showed that when your body is fighting an infection, the immune cells that store vitamin C get depleted. So, taking more vitamin C when you’re sick may improve those cells.
One study found that consuming high doses of vitamin C (approximately 8 grams daily) benefited cold treatment if administered within 24 hours of having cold symptoms and continued for 5 days. Still, the research on whether vitamin C can prevent a cold is inconclusive.
Vitamin C is found naturally in foods like oranges, bell peppers, and strawberries, and it certainly won’t do us any harm. But what about the massive doses found in vitamin C supplements and products like Airborne and Emergen-C?
A tablet of Airborne, for instance, contains 1,000 milligrams of vitamin C (equivalent to 11 glasses of OJ) along with zinc, vitamins A and E, selenium, and a blend of herbs including ginger and echinacea.
Emergen-C also contains 1,000 milligrams of vitamin C (1,667 percent of the recommended daily value) and recommends users take it up to two times daily. Each serving also includes B vitamins, zinc, and electrolytes, which is why it claims to enhance energy (without the caffeine crash).
While neither of them outright say that they can prevent or cure colds, the mega doses of vitamin C are generally the reason many cold-sufferers sniffle their way to the supplement aisle.
While there are no product-specific studies testing Airborne and Emergen-C’s effectiveness in preventing and treating the common cold, research that looks at ingredients like vitamin C and zinc can give us some insight into how well the products work.
A 2013 research review showed that vitamin C is water-soluble, so when taken in excess, it at least won’t build up in your tissues like fat-soluble vitamins can.
As we’ve mentioned, the research on vitamin C is mixed, but according to the National Institutes of Health, many health professionals maintain that it’s not an effective treatment.
Research on zinc is positive but still pretty inconclusive. A 2011 research review found some evidence that taking a zinc supplement soon after the onset of symptoms could significantly reduce the duration and severity.
Researchers are still working on how much, how often, and when to take it for max effect.
There are still a few things to consider before overdoing it on the fizzy drinks. For example, a 2013 study showed that too much vitamin C can cause diarrhea, nausea, stomach cramps, and kidney stones.
The National Institutes of Health suggest that adults consume no more than 2,000 milligrams of vitamin C each day.
Similarly, too much vitamin A (which is often included in these immune boosters) might do more harm than good. According to the National Institutes of Health, excess doses of more than 3,000 IU per day can cause dizziness, nausea, headaches, coma, and (in rare cases) death.
In other words, it is possible to have too much of a good thing. So, when it comes to catching a bug, it’s probably best to save money on the hype and listen to the classic recommendations: Get lots of sleep, wash your hands, and cook some chicken soup.
While regularly consuming adequate amounts of vitamin C may help reduce the frequency of catching colds, there’s little evidence that it can actually help prevent sickness once it’s already set in.
But a moderate amount of vitamin C taken when you first feel those symptoms hit you may help reduce the duration and severity.
Try getting it through food first, then consult your healthcare professional if you think you need to amp it up to supplement form.