People who take vitamin C regularly are being urged to stop if they notice certain symptoms, according to the NHS and other health experts. The vitamin is taken by millions across the UK and is a popular choice for boosting the immune system, and can help in reducing the severity of a cold.

January is a peak month for catching coughs and colds, as well as common 'winter bug' viruses, like norovirus. Besides practising good hygiene daily, keeping your immune system in top shape is another way of protecting yourself against nasty illnesses.

Maintaining a healthy diet is the best way of giving your body everything it needs to fight off germs. However, for some people, taking that extra bit of help in the form of a vitamin supplement, especially if prescribed by their doctor, can help, too.

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Vitamin C is a strong antioxidant that helps protect cells from damage caused by free radicals and supports the immune system. It's also really important for making collagen, which keeps skin, blood vessels, bones, and cartilage healthy. Plus, it helps bodies absorb iron better and is useful for healing wounds. Lack of vitamin C can lead to scurvy.

The NHS says: "Adults aged 19 to 64 need 40mg of vitamin C a day. You should be able to get all the vitamin C you need from your daily diet. Vitamin C cannot be stored in the body, so you need it in your diet every day."

Taking large amounts (more than 1,000mg per day) of vitamin C can cause side effects. The NHS says these symptoms 'should disappear once you stop taking vitamin C supplements', however, others may require medical intervention.

Side effects include, number one, diarrhoea. However, people may also experience three other side effects, such as nausea, flatulence and stomach cramps. This happens because the body can't take in too much, which causes an osmotic effect in the digestive system. Usually, the symptoms go away if you lower the dosage or stop completely.

Another risk of taking too much vitamin C is kidney stones. The NHS says: "Your body will absorb any Vitamin C in your diet and convert it to oxalate, which then goes on to form stones in your kidneys. You should not need to take vitamin supplements if you have a varied diet including fruit and vegetables."

Taking a lot of Vitamin C supplements (usually more than 1,000 mg a day) can raise the chance of getting calcium oxalate kidney stones. This happens because the body turns extra vitamin C into oxalate, which is then passed out in the urine.

Even though vitamin C from food is safe, high doses from supplements can lead to higher levels of oxalate in urine. People who have had kidney stones are often told to stay away from them.

According to the NHS, very small kidney stones are "unlikely" to cause many symptoms. It adds: "They may even go undetected and pass out painlessly when you urinate". However, larger kidney stones can cause symptoms, including the following seven warning signs:

Speak to your doctor if you are taking vitamin C and experience any of these eleven symptoms, or if you have any health questions or concerns. Avoid making any drastic diet and lifestyle changes before consulting your GP.

The Department of Health and Social Care says you should be able to get all the vitamin C you need by eating a varied and balanced diet. If you take vitamin C supplements, do not take too much, as this could be harmful. Taking less than 1,000mg of vitamin C supplements a day is unlikely to cause any harm.

Vitamin C is found in a wide variety of fruit and vegetables. Good sources include:

• citrus fruit, such as oranges and orange juice


• peppers


• strawberries


• blackcurrants


• broccoli


• brussels sprouts


• potatoes