Around 1970, Nobel prize winner Linus Pauling popularized the theory that vitamin C helps treat colds.

He published a book about cold prevention using megadoses of vitamin C, or up to 18,000 mg daily. For comparison, the RDA is 75 mg for women and 90 mg for men.

At that time, no reliable studies had proved this to be true.

But in the following few decades, multiple randomized controlled studies examined whether the vitamin had any effect on the common cold.

The results have been fairly disappointing.

An analysis of 29 studies including 11,306 participants concluded that supplementing with 200 mg or more of vitamin C did not reduce the risk of catching a cold (1Trusted Source).

However, regular vitamin C supplements had several benefits, including:

• Reduced cold severity: They reduced the symptoms of a cold, making it less severe.
• Reduced cold duration: Supplements decreased recovery time by 8% in adults and 14% in children, on average.

A supplemental dose of 1–2 grams was enough to shorten the duration of a cold by 18% in children, on average (1Trusted Source).

Other studies in adults have found 6–8 grams per day to be effective (2Trusted Source).

Vitamin C appears to have even stronger effects in people who are under intense physical stress. In marathon runners and skiers, vitamin C alantost halved the duration of the common cold (1Trusted Source).

Summary Although vitamin C supplements have no effect on the risk of catching a cold, they appear to reduce its severity and duration.

Vitamin C is an antioxidant and necessary to produce collagen in the skin.

Collagen is the most abundant protein in mammals, keeping skin and various tissues tough but flexible.

A vitamin C deficiency results in a condition known as scurvy, which isn't really a problem today, as most people get enough vitamin C from foods.

However, it’s less known that vitamin C is also highly concentrated in immune cells and quickly depleted during an infection (3Trusted Source).

In fact, a vitamin C deficiency significantly weakens the immune system and increases the risk of infections (4Trusted Source).

For this reason, getting enough vitamin C during an infection is a good idea.

Summary Vitamin C is essential for the proper functioning of immune cells. It is depleted during infections, so a vitamin C deficiency may increase their risk.

There is no cure for the common cold.

However, some foods and nutrients can help the body recover. In the past, people have used various foods to reduce their symptoms.

Few of these are scientifically proven to work, but some are backed by evidence.

• Flavonoids: These are antioxidants found in fruits and vegetables. Studies suggest that flavonoid supplements may reduce the risk of infections in the lungs, throat and nose by 33%, on average (5Trusted Source).
• Garlic: This common spice contains some antimicrobial compounds that may help fight respiratory infections. Read this detailed article for more information (6Trusted Source).

Summary Several other nutrients and foods may help you recover from a cold or even reduce the risk of catching one. These include flavonoids and garlic.

Supplementing with vitamin C won’t reduce your risk of catching a cold, but it may speed up your recovery and reduce the severity of your symptoms.

While taking supplements may be necessary to reach the high vitamin C intake required to improve colds, make sure not to go overboard.

That’s because too much vitamin C has some adverse side effects.

To meet your basic nutrient requirements, whole foods are generally a better idea. Good examples of healthy foods that are high in vitamin C include oranges, kale and red bell peppers.