Guide to vitamin C

Vitamin C is probably the most well-known vitamin, one we all need daily as it can't be stored in the body and is water-soluble.

It’s found in fruit and vegetables including citrus fruits, green leafy vegetables, tomatoes and berries.

Eating five portions of fruit and vegetables a day should give you more than enough vitamin C. However, the UK’s National Diet and Nutrition Survey published in 2016 found only eight per cent of children aged 11 to 18, 27 per cent of adults aged 19 to 64 and 35 per cent of those aged 65 and over met the five-a-day recommendation.

Dr Sarah Brewer says: Vitamin C is important in the immune system and may shorten the duration of the common cold. It is also needed to make collagen, an ingredient that helps build healthy skin, and cartilage in the joints. Supplements may be a good way to top up if you’re not eating enough fresh fruit and vegetables.

What does vitamin C do?

Vitamin C (also known as ascorbic acid) is an antioxidant which protects cells in the body from damage by free radicals; these are unstable oxygen molecules caused by everyday processes such as breathing and eating, but also pollution and smoking. It is believed the build-up of free radicals may contribute to the ageing process and the development of conditions such as heart disease.

Vitamin C also plays a key role in the growth and repair of tissues all over the human body. It also helps the body make collagen, an important protein which is used to make skin, tendons, cartilage and ligaments as well as blood vessels.

Common cold

Vitamin C’s antioxidant properties have been found to help the body fight off colds quicker, although whether it can prevent you from catching one is less certain. A 2013 review of studies concluded regular doses of 200mg or more of vitamin C didn't influence common cold incidence in the general population but did shorten their duration (by eight per cent in adults and 14 per cent in children).

The review also said vitamin C was particularly useful for preventing colds in people during periods of extreme physical exercise (including marathon runners and skiers), when it halved the risk.


Cataracts are a common eye condition that affect most people over 60 to some degree. They form when the normally clear lens in the eye becomes cloudy and this affects vision.

Researchers from King’s College in London published a study of twins in 2016 which found eating a diet rich in vitamin C could cut the risk of cataract progression by one third. 

Heart health

Vitamin C’s strong antioxidant effects may protect the arteries from oxidative stress and slow the progression of arteriosclerosis (hardening of the arteries), although the evidence on this is mixed.  It's also thought to a play a role in lowering blood pressure and reducing uptake of harmful LDL cholesterol, a waxy substance made in the liver which can clog the arteries.

A 2015 Danish study of 97,000 people found a high intake of fruit and vegetables was associated with both a lower incidence of cardiovascular disease and dying from all causes. Researchers concluded it was possible these beneficial effects may be driven by the high vitamin C content in fruit and vegetables.

Getting vitamin C from your diet

Oranges, lemons, watermelon, mango, leafy green vegetables and broccoli, strawberries, red and green peppers, fresh tomatoes, blueberries, squash and cranberries are all good sources of vitamin C.

Vitamin C deficiency causes a disease called scurvy, where the body can't make enough collagen and tissue in the body breaks down causing muscle and joint pain, tiredness, a skin rash and bleeding, swollen gums. It’s very rare in the UK but may affect some people on low incomes, the elderly who eat poor diets, and heavy smokers. There are reports that it is on the increase.


Vitamin C is well-tolerated in most people. There's no upper safe daily limit set, but stomach upsets have been reported at doses of more than 1,000mg a day.

Correct dosage

The UK’s recommended daily nutritional intake (RNI) is 40mg for adults, 50mg for pregnant women and 70mg for women while breastfeeding. Supplements are available at a range of doses, a typical one is 500mg to 1,000mg a day.

Vitamin C is important in the immune system and may shorten the duration of the common cold. It is also needed to make collagen, an ingredient that helps build healthy skin, and cartilage in the joints.

Dr Sarah Brewer


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