Can vitamin C help with cancer and common colds?

Linus Pauling was a 20th-century American chemist and biochemist, amongst other things. Although awarded the highly respected Nobel Prize in Chemistry, his work on vitamin C generated much controversy. Claims that high dose vitamin C intake could work miracles with colds or cancer, for example, were widely criticised within the health and scientific communities and he was branded as a ‘quack’.


Cancer and complementary medicine have always been a ticklish subject. Whereas, colds and complementary medicine, not as much. Even though I write this article with enormous care, it has the potential to draw scrutiny, and rightfully so. Cancer Research UK (1) admits that although some complementary therapies can help people to feel better, some types might not be safe in certain situations. For example, some might obstruct conventional treatments from working as efficiently as they should.

What is vitamin C?

Just in case you did not get the clue in the name, vitamin C (aka ascorbic acid) is a vitamin. Vitamins are a group of essential substances that are needed for normal cell function. Vitamin C is necessary for the proper function and development of many parts of our body. It also plays an important role in healthy immune function.

Vitamin C is an antioxidant. Antioxidants are wonderful compounds that can prevent or slow down damage to the cells in our body. 

Our human body does not produce vitamin C, so sufficient levels must be obtained from our diet or other sources. Deficiency is rare because vitamin C is found in a wide variety of fruits and vegetables. This is one of the many great reasons to try and get in your 5 a-day portions of fruits and vegetables.

Vitamin C and colds

The common cold is a mild viral infection of the upper airways. Most people recover from the virus in approximately seven to 10 days. According to the Office for National Statistics (2), minor illnesses like coughs and colds accounted for almost a third of sick days in 2018. Can vitamin C potentially help reduce the (real) sick days caused by common colds?

Most research shows that taking one or two grams of vitamin C supplements daily reduces the severity of a cold by decreasing the effects of irritating symptoms such as a runny nose, sore throat and coughing (3). It has additionally been shown to reduce a cold’s duration by 1-1.5 days - that sounds good to me; every little helps. Some employers may read this and feel inspired to send fruit or supplement baskets out to sick employees, or not, one can be optimistic. 

Vitamin C and cancer

Cancer is a condition where abnormal cells in the body divide in an uncontrolled way. Rather shockingly, it is predicted that 1 in 2 people in the UK will get cancer in their lifetime. Currently, three million people are estimated to be living with a cancer diagnosis. This is forecasted to increase to four million by 2030 (4). Cancer and its treatments can affect body systems, such as the immune system and the hormone system. Which brings us on to a certain vitamin that plays an important role in healthy immune system performance.

A 2018 scientific review (5) stated that cancer patients can often experience vitamin C deficiency. The vitamin C deficiency is habitually connected to/with reduced vitamin C intake, inflammation, infection, disease processes, and treatments such as radiation, chemotherapy, and surgery. We already understand that vitamin C deficiency can be problematic by itself and cause cells not to function properly. Like with any deficiency, but especially in the presence of cancer, the deficiency should be addressed to promote healthy functioning of the body’s systems as much as possible.

The review referenced various studies that reported reductions in indicators of inflammation as a result of the administration of intravenous (IV) vitamin C, which was used with different types of cancers.

This may suggest some improvement in symptoms, with a possible benefit in quality of life, when vitamin C IV therapy alone or in combination with oral vitamin C is used in oncologic care as a supportive therapy.

Food sources of vitamin C

Fruits and vegetables are great food sources of vitamin C. More specifically, citrus fruits, tomatoes, red and green peppers, kiwi fruit, broccoli, strawberries, brussels sprouts, and cantaloupe are rich food sources.

Safety of vitamin C

Oral vitamin C supplements are generally considered safe. Side effects tend to be related to the quantity that is taken. The daily tolerable upper intake level of vitamin C for adults is 2,000 mg (2g).

The most common complaints are diarrhoea, nausea, abdominal cramps, and other gastrointestinal disturbances. The chance of getting these side effects increases the more vitamin C you take. It is best to keep to 2,000 mg or less.

Can vitamin c help with cancer and common colds?

Research does not show vitamin C to be the cure for all ailments as Linus Pauling may have claimed. But vitamin C is essential for the healthy functioning of our immune system, which helps us fight off viruses, bacteria, and foreign bodies that cause infection or disease.

Vitamin C has been shown to reduce the severity and duration of a cold. It has also been shown to decrease inflammation and may improve symptoms related to disease processes and side effects of standard cancer treatments. But before you rush to your local health shop, as with all dietary and supplement information, please seek medical advice first. Everybody is different, and what one person needs can differ greatly from another.

Registered Nutritional Therapists (RNTs) can aid those looking to better support their body, during and after medical treatment for cancer. RNTs who have experience in working with cancer patients will be able to work with individuals to ensure the diet is as balanced and nutritious as possible.

RNTs never recommend nutritional therapy as a replacement for medical advice or treatment. They frequently work alongside medical professionals and will communicate with other healthcare practitioners involved in a client’s care. 


1. The safety of complementary and alternative therapies | Cancer Research UK [Internet]. 2020 [cited 2 February 2020]. Available from:

2. Sickness absence in the UK labour market - Office for National Statistics [Internet]. 2020 [cited 2 February 2020]. Available from:

3. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2013;.

4. Maddams J, Utley M, Møller H. Projections of cancer prevalence in the United Kingdom, 2010–2040. British Journal of Cancer. 2012;107(7):1195-1202.

5. Klimant E, Wright H, Rubin D, Seely D, Markman M. Intravenous vitamin C in the supportive care of cancer patients: a review and rational approach. Current Oncology. 2018;25(2):139.

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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London E18 & E10
Written by Rochelle Logan-Rodgers, Elle Rock Nutrition (BSc PgDIP mBANT mCNHC)
London E18 & E10

Rochelle is a fully Registered Nutritionist MBANT and Registered Nutritional Therapist MBANT & CNHC. Her qualifications include a Postgraduate Diploma in Nutritional Therapy from Middlesex University with the Northern College of Acupuncture. She did also obtain a BSc (Hons) in Molecular Medicine, at the University of Sussex.

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