- How much vitamin C do you need to stay healthy?
Does vitamin C help with colds? We know that vitamin C, or ascorbic acid as it’s also known, is necessary for the proper functioning of our immune system. So it makes sense that many of us take to popping this supplement when we feel under the weather, or as a preventative method when the weather gets cooler. But is there any evidence that it actually works?
The theory that vitamin C protects us against seasonal sniffles is relatively new, with Nobel prize winner Linus Pauling popularizing it in the early 70s. At the same time, he did not have any hard evidence to support his claim. In the following decades, many scientists tried to determine the exact effect of vitamin C on common colds, but their findings were mostly disappointing. And what’s more, recent studies have produced mixed results. So the answer to the question ‘does vitamin C help with colds?’ may not be straightforward.
So should you supplement vitamin C? Here, we look into the latest research to help you decide whether it’s worth your buck. However, it is best consult your doctor before you make any changes to your dietary routine.
What is vitamin C?
Vitamin C plays many important roles in our body, and is critical to the formation of many different tissues.
“Vitamin C is a necessary vitamin for producing collagen in the skin,” says Dr. Ioannis Liakas, medical doctor and medical director at Vie Aesthetics (opens in new tab). “Collagen is the most abundant protein in mammals, maintaining the skin and various tissues in our body tough, yet flexible. In general, a vitamin C deficiency is linked to a weakened immune system and an increase in the risk of infections.” Ascorbic acid also helps with the production of hormones, energy metabolism, neutralizing free radicals and absorbing iron in the digestive tract.
Dr. Ioannis Liakas
Dr. Ioannis Liakas has decades of experience as an NHS Consultant of Internal Medicine and Gerontologist in the U.K. He is a Fellow of the Royal College of Physicians (FRCP), Honorary Senior Lecturer at Queen Mary Medical School, and a Member of the British College of Aesthetic Medicine.
- Related: Which foods boost the immune system?
Does vitamin C have any effect on colds?
When it comes to vitamin C’s effect on colds, studies tend to produce mixed results. According to a review in the Frontiers in Immunology (opens in new tab) journal, there are currently no clinical recommendations that support using high-dose supplements of vitamin C to decrease the risk of respiratory infections in the general population. However, this practice may be advised for certain groups (such as athletes or the military) and for individuals who show signs of vitamin C deficiency.
Vitamin C supplementation may also be recommended for those at high risk of severe infection (such as the obese, diabetics or the elderly), as it may help lower inflammation (opens in new tab).
“Getting enough ascorbic acid during an infection is a great idea,” says Dr Liakas. “However, this does not mean that vitamin C can completely and effectively prevent you from getting a cold during the winter months. There is not enough evidence to show that vitamin C is an effective preventative treatment for the common cold. Instead, we know that a severe deficiency can make it harder for our bodies to fight off infection. This means that, over time, not getting enough vitamin C may increase your risk of getting sick.”
At the same time, scientists from the Life (opens in new tab) journal argue that most of current recommendations are based on highly biased studies from the late 70s. They claim that the articles from JAMA and the American Journal of Medicine rejected the evidence that vitamin C is effective against the common cold, and that their negative stance helped shape this ‘prejudiced’ discourse for years to come.
So what are the latest scientific developments regarding vitamin C and common cold — and can they provide us with definite answers?
Does vitamin C help with the prevention of colds?
According to the Nutrients (opens in new tab) journal, vitamin C is critical for maintaining the integrity of our epithelial barriers — all of the surfaces that stop any external contaminants from entering our body. Skin and intestinal walls are good examples of epithelial barriers.
Vitamin C also helps to protect our skin from pathogens by strengthening its structure and promoting its ability to ‘scavenge’ free radicals, and enhances the ability of our immune system to detect and destroy microbes before they start posing danger to our health. So in theory, vitamin C should protect us from these minor respiratory infections.
But according to a major Cochrane systematic review (opens in new tab), there is no evidence that vitamin C supplementation reduces the incidence of colds in the general population. However, it may be useful for people exposed to brief periods of severe physical exercise. Intense exercise significantly increases oxidative stress and as such, it may weaken the epithelial barriers and increase the chance of catching infections.
Does vitamin C help with the treatment of colds?
According to the Nutrients (opens in new tab) journal, vitamin C helps increase the production and proliferation of B- and T-lymphocytes. B-lymphocytes make antibodies — proteins that bind to bacteria and viruses. This process helps our immune system identify them as foreign bodies. The role of T-lymphocytes is to destroy these marked unwanted visitors. So again, in theory, vitamin C should help us shorten the duration and ease the symptoms of common colds.
And according to a meta-analysis published in the Biomed Research International (opens in new tab) journal, vitamin C can indeed help shorten the duration of colds. The time for symptom improvement and overall recovery time were better with vitamin C supplementation than with antiviral therapy alone. Results from another meta-analysis published in the Biomed Research International (opens in new tab) journal suggest that taking extra therapeutic doses at the onset of cold may also help shorten the duration of cold, as well as relieve the symptoms like chest pain, fever and chills.
- Related: Which vitamins boost the immune system?
How much vitamin C do you need to stay healthy?
The recommended daily allowance (RDA) for vitamin C depends on several factors, including age and gender. According to the NIH (opens in new tab), women should aim for 75 mg of vitamin C per day, whereas men need 90 mg. Pregnant and breastfeeding women should increase their intake. Depending on their age, they may need between 80mg to 120 mg a day. individuals who smoke also require 35 mg more per day than non-smokers.
Vitamin C is water soluble, which means that it is not stored by the body and is filtered out by the body in urine. However, high doses of vitamin C may produce unwanted side effects. The upper limit is set at 2g of this nutrient a day.
Check out these nine sources of vitamin C to boost your immune health.
This article is for informational purposes only and is not meant to offer medical advice.
Anna Gora is a Health Writer for Future Plc, working across Coach, Fit&Well, LiveScience, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a BSc degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.
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Last Update: October 8, 2020; Next update: 2023. Taking vitamin C every day to try to prevent colds won't protect most people from colds. It only slightly shortens the amount of time that they're ill. Starting to take vitamin C once you already have cold symptoms won't have any effect on your cold.What vitamin helps fight off a cold? ›
Vitamins C and D, zinc, and Echinacea have evidence-based efficacy on these immune system barriers.How much vitamin C should I take for a cold? ›
A supplemental dose of 1–2 grams was enough to shorten the duration of a cold by 18% in children, on average ( 1 ). Other studies in adults have found 6–8 grams per day to be effective ( 2 ). Vitamin C appears to have even stronger effects in people who are under intense physical stress.How do you shorten a cold? ›
- Stay hydrated. Water, juice, clear broth or warm lemon water with honey helps loosen congestion and prevents dehydration. ...
- Rest. Your body needs rest to heal.
- Soothe a sore throat. ...
- Combat stuffiness. ...
- Relieve pain. ...
- Sip warm liquids. ...
- Try honey. ...
- Add moisture to the air.
Zinc, selenium and vitamin D are known for boosting the immune system. Specifically, a 2013 review of 17 studies found that taking zinc supplements within 24 hours of the onset of symptoms reduces the duration of common cold symptoms. Tip to remember: Supplements are beneficial in moderation.