Colds and flu

Updated 09 March 2015

Could vitamin C therapy cure a cold?

Because humans don't produce their own vitamin C, it is important that we get enough of this vital nutrient on a regular basis.


When we get a cold, the first thing we are told is to get some vitamin C into our bodies. Even though a number of studies have found that taking vitamin C doesn’t prevent us from getting colds and flu, it does appear to strengthen our immunity – so, basically, the advice is good, and at the very least can’t do any harm.

Everyone knows how vitamin C in lemons cured scurvy in the eighteenth century, but the first doctor who started using vitamin C aggressively to treat illness was Frederick R. Klenner in the 1940s. He cured polio, measles, mumps, tetanus, chicken pox and a number of other diseases with massive doses of vitamin C.  

This may sound like a tall story, but Dr Klenner used vitamin C therapy for over forty years and wrote many medical papers on the subject which can be found in the Clinical Guide to the Use of Vitamin C, edited by Lendon H. Smith, M.D.

Humans lost an enzyme

An interesting fact is that there are only four groups of mammals that do not produce vitamin C in their bodies, i.e. humans, other primates (e.g. apes and monkeys), guinea pigs and fruit bats.

The reason for this phenomenon is that of the four enzymes needed to convert glucose into vitamin C we have only three. Humans lost the fourth (L-gulonolactone Oxidase) somewhere during the course of our evolution – presumably because our diets were abundant in vitamin C.     

In mammals that produce their own vitamin C, it is created mainly as a response to stress. Under normal circumstances a mammal the size of the average human being (±70kg) produces 5,000 to 10,000 milligrams per day. However, when the animal is under stress, it produces four times that amount. When under stress a goat can make up to 100,000 milligrams of vitamin C!

Is our RDA for vitamin C too low?

The recommended daily allowance (RDA) of this vitamin for humans is below 100 milligrams per day, which seems rather low and could be the reason why animals that make a lot of vitamin C are much less prone to the diseases that we suffer from. They can also live up to 10 times beyond their physical maturity, compared to a maximum of 4 times for humans. Hypothetically, this means that if we take 20 as the age of physical maturity for humans, we could live up to 200 years if we produced our own vitamin C.

Read: RDA for vitamin C should be more

Dr Thomas Levy, author of Vitamin C, Infectious Diseases, and Toxins: Curing the Incurable maintains that “a human's inability to make the enzyme L-gulonolactone Oxidase must be considered an inborn error of metabolism” and that doctors should “consider this lack of enzyme activity in every medical condition”.

Linus Pauling

Perhaps the most famous name in the field of vitamin C research is Linus Pauling, one of the most important scientists of the 20th century. Pauling is the only person who ever received two unshared Nobel Prizes: the Nobel Prize in Chemistry (1954) and the Nobel Peace Prize (1962).

Pauling became interested in the idea of high-dose vitamin C in 1966 and started taking 3 g per day. In 1970 he published Vitamin C and the Common Cold which helped to make vitamin C popular with the public. His best known book on health and vitamin therapy is How to Live Longer and Feel Better (1986).

Read: Natural cures for the common cold

In Vitamin C and the Common Cold, Pauling encouraged people to take a daily dose of 3,000 milligrams of vitamin C, which is 50 times the RDA. He believed that this would wipe out the common cold. The medical fraternity wasn’t quite as enthusiastic, and a number of scientific tests indicated that vitamin C did not “have any important effect on the duration or severity of infections of the upper respiratory tract”.

He also believed that vitamin C could cure cancer and refused to be put off by strong opposition from the scientific and medical establishments.

Oral vs. intravenous

Pauling found that cancer patients who received vitamin C lived four times longer than those who received no vitamin C. High-dose vitamin C was administered as sodium ascorbate, given orally and intravenously.

Read: Intravenous vitamin C boosts chemotherapy action 

Dr. Charles Moertel of the Mayo Clinic, who was the main opponent of Pauling’s thesis set about disproving his findings. In his tests he administered large amounts of oral vitamin C to the patients in his group, and when they failed to show improvements over patients not receiving vitamin C in the study, Moertel announced that Pauling’s hypothesis was wrong. He had conveniently forgotten that Pauling’s patients received both oral and intravenous vitamin C.  

This had a considerable impact on the reputation of vitamin C as an effective tool against cancer for a number of years, but in recent times people like Dr Hugh Riordan of Kansas have validated the benefits of intravenous vitamin C. Studies have indicated that oral vitamin C is poorly absorbed and that given intravenously it is much more effective against cancer.

Vitamin C has to be constantly replenished

Nowadays vitamin C is back in favour and is being used to protect against conditions as diverse as high blood pressure, heart disease, asthma, and cancer.   

Even the National Cancer Institute (NCI) which forms part of the U.S. Department of Health and Human Services is singing the praises of vitamin C in the battle against cancer, and states in an overview of high-dose vitamin C: “Laboratory studies have reported that high-dose vitamin C has pro-oxidant properties and decreased cell proliferation in prostate, pancreatic, hepatocellular, colon, mesothelioma, and neuroblasoma cell lines."

Because vitamin C is a water-soluble vitamin it cannot be stored in the body for long and has to be replenished on a regular basis. Some of the best dietary sources of vitamin C are:

  • Bell peppers
  • Guavas
  • Dark green leafy vegetables
  • Kiwi fruit
  • Broccoli
  • Berries
  • Citrus fruits
  • Tomatoes
  • Peas
  • Papayas

Read more:

Do I need a vitamin C supplement?
How Vitamin C boosts your immune system
Top 10 foods with vitamin C

Image: Vitamin C from Shutterstock


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Flu expert

Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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