Vitamin C and the common cold: What does the science say?
If you've ever had a cold, you know that the best way to get over it is by getting lots of rest and drinking plenty of liquids. For those who want something more active, there's always vitamin C. It has long been touted as a natural cure for colds and flu. But does it work? Or is this another case where science doesn't support old wives' tales?
If a cold is coming on, doctors often recommend taking vitamin C, but there's little evidence that it will help
If you're feeling a cold coming on and have been advised by your doctor to take vitamin C, it's unlikely that they are referring to the pill form you can pick up at any drugstore. Instead, they mean foods rich in vitamin C—like oranges, strawberries, kiwi fruit, broccoli, and peppers—and supplements.
But while these two nutrient sources may benefit your overall health (and even protect against cancer), there isn't much scientific evidence that either prevents colds. Most studies had found little effect on expected cold duration when people took high doses of synthetic ascorbic acid (also known as vitamin C) within 24 hours after symptoms first appeared.
There are signs of benefit during the early stages of a cold, and even then, the effect is not enormous
Don't hold your breath if you're taking vitamin C to help prevent colds.
Research suggests there may be some benefit to taking a vitamin C supplement during the first day or two of feeling ill with a cold—but even then, the effect is not enormous. It's also unclear whether supplements can help with symptoms later in the illness.
"I think it's tough to say there's any real benefit [of vitamin C] for common cold prevention," says Dr. Michael Hochman, an associate professor at The University of Iowa Roy J. and Lucille A. Carver College of Medicine who studies viral infections and their treatment.
The best available evidence suggests taking vitamin C regularly does not reduce the risk of catching a cold and only has an effect if you're under significant physical stress
The best available evidence suggests taking vitamin C regularly does not reduce the risk of catching a cold and only has an effect if you're under significant physical stress.
It's important to remember that most of these studies were based on self-reported illnesses, which can be inaccurate. If you're lucky, you'll only suffer from one or two colds per year, so it's unlikely that taking vitamin C regularly will give you any noticeable benefit. Vitamin C is essential for your health, but extra vitamin C won't prevent or treat colds.
Most of the studies were based on self-reported illnesses, which can be inaccurate
While some studies were based on self-reported illnesses, often inaccurate and subject to bias, others relied on clinical diagnoses of colds or other respiratory infections.
The most recent research also highlighted significant differences in the effectiveness of vitamin C when taken for a short period versus daily over an extended period.
A 2013 meta-analysis concluded that there was no evidence that vitamin C reduced the risk of developing colds in healthy people with standard immune systems.
The doses used in the studies were higher than what's typically recommended
The doses used in the studies were higher than what's typically recommended. The researchers wanted to determine if vitamin C effectively prevented colds. Hence, they gave participants enough of it to ensure their bodies had plenty of vitamin C.
A 1000mg dose of vitamin C should be enough for anyone, but some people may need more depending on their age and gender (for example, women who smoke are at greater risk of developing scurvy). Anyone with a healthy diet with lots of fruits and vegetables should be getting more than enough from food alone—but if you want an extra boost or have been feeling run down lately, taking 1000mg per day could help prevent getting sick.
Vitamin C deficiency is rare in Australia since most people eat plenty of fresh fruit and vegetables each day as part of a balanced diet; however, if your diet consists mainly of junk food, then you may want to consider taking supplements daily until you start eating healthier again (the same goes for folic acid). An orange contains around 90mg, so eating one or two oranges daily should provide all the vitamin C your body needs without any side effects."
People who are vitamin C deficient may benefit from extra vitamin C
If you're vitamin C deficient, it makes sense to take in more of the nutrient. People who are vitamin C inadequate may benefit from extra vitamin C.
People with a known deficiency should speak with their healthcare provider about how much extra vitamin C to take and how long.
Some believe high doses of vitamin C will help prevent or treat the common cold, but the evidence is mixed. In some studies, people with certain conditions who took large amounts of supplemental vitamin C experienced fewer infections like colds than those who took only one or two grams. However, other studies have found no effect of supplementation on infection rates in non-deficient populations (4). A meta-analysis also found no benefit overall (5).
Vitamin C is essential for your health, but extra vitamin C won't prevent or treat colds
Vitamin C is an essential nutrient for the human body. It plays a role in immune function, wound healing, and bone and eye health. Vitamin C is obtained from food sources such as fruits and vegetables.
Some research suggests that taking a high daily dose of vitamin C can help to reduce your risk of developing a cold when exposed to cold viruses. However, this research has been inconsistent, and it's not clear what dose of vitamin C is needed for the potential benefit or whether other nutrients, such as zinc, may be necessary for preventing colds.
In conclusion, we can say that the evidence is not yet clear on whether vitamin C can prevent or treat colds. There are some signs of benefit during the early stages of a cold, and even then, the effect is not enormous. However, this may be more likely if you're under significant physical stress. If you want to take vitamin C regularly to reduce your risk of catching a cold, then it's best to consult with your doctor, who will advise accordingly based on their knowledge and experience.