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Vitamin C for the Common Cold

The Vitamin C Debate

Is vitamin C effective at preventing a cold or other virus? Does eating foods high in vitamin C or taking C supplements reduce the duration or severity of sickness? The effect of vitamin C on the common cold has been a subject of debate for more than 70 years with numerous studies attempting to tease out a cause and effect relationship (Hemila, 2013). While the idea that vitamin C is effective against colds and other viruses predates Dr. Linus Pauling, he was most certainly influential in drawing a great deal of attention to the debate.

Dr. Linus Pauling Says Vitamin C Cures Colds

Linus Pauling, Ph.D. (1901-1994) was an American chemist who won two Nobel prizes, one for chemistry in 1954 and the other for peace in 1962. Pauling is largely credited for the widespread belief that high doses of vitamin C are effective against colds and other illnesses. In 1970, Pauling published Vitamin C and the Common Cold proclaiming that taking 1,000 mg of vitamin C daily reduces the incidence of colds by 45% for most people, while some may require much larger amounts. In his 1976 revision of the book, retitled Vitamin C, the Common Cold and the Flu, Pauling suggested even higher dosages.

Pauling not only published books on the subject, he also counseled doctors on the use of therapeutic doses of vitamin C and was known to take large quantities of ascorbic acid himself. Dr. Pauling reported 12,000 mg daily dose is 6 x today’s tolerable upper intake levels for vitamin C (2,000 mg/day for adult males and females). He was known to take a much higher dose of 40,000 mg if he experienced symptoms of a cold. Pauling may very well have been the driving force popularizing vitamin C supplements which are the third most-popular supplement among U.S. adults today, after multivitamins and vitamin D (CRN, 2019). But the question remains as to the effectiveness of ascorbic acid for preventing and reducing the duration and symptoms of the common cold.

What Makes Vitamin C So Unique

The foundation of Dr. Pauling’s argument for high dose supplementation of vitamin C perhaps began with a basic observation he made of a key difference between humans and most other animals. Dr. Pauling begins his argument for vitamin C mega-dosing by pointing out something unique about ascorbic acid. While most other vitamins required by humans are also required by other animals, that is not the case for vitamin C. Most animals (99% or more) don’t require vitamin C because they synthesize it. Pauling frames his argument in a lecture saying,

“If I ask why do these animals continue to synthesize vitamin C even though they may be getting large amounts by ordinary standards in their diet to several grams a day for an animal the size of a man. The answer surely is that they continue to synthesize ascorbic because the amounts they get in their diet are not enough to put them in the best of health. Not enough to put them in the fittest condition in the environments in which we live.” (Pauling, 2019)

Does vitamin C prevent or reduce severity of colds and viruses? Whole plant foods are excellent sources of vitamin C.
Whole plant foods all contain vitamin C in various amounts. Its no surprise that people and animals who consume whole plant foods in abundance receive large daily doses of this essential vitamin.

Pauling noticed that natural foods, in the form of whole plant foods consumed by all nonhuman primates, contain vastly greater quantities of vitamin C than those found in the modern human diet.

“When I looked at 150 raw natural plant foods taking the amounts that would give 2,500 kilocalories of energy, I found that for thiamine and other vitamins there was perhaps three times or  five times as much of the vitamin than is now recommended as you get in modern diet on the average, but 50 times as much vitamin C as is recommended, and I thought this is an indication that larger amounts of vitamin C are needed, because animals are getting these larger amounts, but to continue to make ascorbate .” (Pauling, 2019)

He also noted that the recommended dietary intake of vitamin C in monkeys is vastly greater than that recommended for humans.

 “Another interesting fact is that the committee that recommends the diet, the food for monkeys, experimental monkeys, recommends seventy times as much vitamin C (monkeys also require exogenous vitamin C, they are primates and all of the primates require this vitamin) seventy times the amount recommended for human beings. I think that this is understandable. Monkeys are very valuable, experimental monkeys. If you’ve spent months carrying out studies with them and then suddenly your monkeys die, it’s a real tragedy. So that a great effort has been made to find out how much vitamin C will put the monkeys in the best of health. No one has gone to the effort to find, to carry out corresponding studies for human beings.” (Pauling, 2019)

Humans are also primates, so this basic observation of the nutritional recommendations for vitamin C in other primates may very well be a valuable insight. Yet Pauling has never been short on critics for his theories surrounding vitamin C.

The Other Side: Casting Doubt on the Effectiveness of Vitamin C

Cedric Wilson from the Department of Pharmacology at the University of Dublin criticized Pauling’s assertions in an editorial published in the British Medical Journal in March 1971. Wilson pointed out that there were then two prevailing theories about the human requirements for vitamin C:

“One specifies that humans require only sufficient exogenous vitamin C to prevent them from degenerating into a scorbutic state. The other theory proposes that human beings should ideally, be saturated with vitamin C. They would then physiologically resemble other animals which can make sufficient vitamin C to keep themselves continually saturated.”

Wilson’s main critique is that the studies Pauling cites to back his theory do not consider the effect of vitamin C metabolism in different individuals and that they fail to interpret the state of ascorbic acid metabolism in the infected subjects during their colds. According to Wilson, without evidence demonstrating that tissue susceptibility is associated with abnormal vitamin C metabolism, Pauling lacks critical evidence needed to validate his theory (Wilson, 1971).

            Five years after Wilson’s critique, a follow up editorial was published in the British Medical Journal in which the evidence surrounding the vitamin C debate was again reviewed. The author makes notes of several studies with conflicting results.

“The first of the two large-scale studies from Toronto concluded that patients receiving large does of vitamin C had significantly less disability from colds and other illnesses that a well-matched placebo group.”

The second study involving 2,349 people during the winter of 1975 didn’t show a dose-response relationship, yet,

“Even so, even in this well-nourished population, large therapeutic doses (4-8 g per day) started at the onset of the illness appeared to reduce the duration and extend of disability from acute infections.”

The authors of the study pointed out the difficulty of diagnosing the common cold in this large population, which may weaken the study’s conclusion.

Another study of schoolchildren, published around this time, claimed a benefit from vitamin C treatment. Both studies were criticized for their difficulty in maintaining “blind” conditions. Two other studies published around the same time claimed no benefit was seen when administering vitamin C therapeutically for patients with colds. Thus, the editorial cast doubt on any practical advancement in treatment derived from the multiple studies attempting to find a cause and effect relationship between vitamin C and the common cold (British Medical Journal, 1976).

29 + Human Trials Find Some Consensus

Yet more than forty years later the scientific debate continues. In 2013 Hemila and Chalker conducted a meta-analysis of 29 studies involving over 11,000 subjects which examined the effect of vitamin C on the common cold. After analyzing the data from these studies they found the regular vitamin C intake reduced the duration of colds in adults by 8% and by 14% in children. Vitamin C also reduced the severity of colds. Other studies found that therapeutic vitamin C had no effect on duration or severity of colds. The authors recommend that,

“Given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them.”(Hemila, 2013)

Hemila and Chalker also add that further studies on the subject are warranted, thus the vitamin C and the common cold debate marches on.

Vitamin C Makes Cold Duration Shorter

In 2017 Hemilla published another analysis of two trials which found that the effects of vitamin C dosage on the duration and symptoms of the common cold may extend to 6-8 grams per day. A press release by the University of Helsinki states,

“Dozens of animal studies using different animal species have found that vitamin C significantly prevents and alleviates infections caused by diverse bacteria, viruses, and protozoa. Given the universal nature of the effect of vitamin C against various infections in different animal species, it also seems evident  that vitamin C influences susceptibility to, and the severity of infections in humans.” (University of Helsinki, 2017)

Hemilla argues that the pooled effect of the scientific studies on the relationship between vitamin C and colds show a highly significant difference between vitamin C and placebo groups indicating a, “genuine biological effect.” The studies examined demonstrate a dose-response relationship between cold duration and vitamin C dose. The first trial gave 3 g vitamin C/day to two groups, 6 g day to one group, and a placebo to a fourth group. The 6 g/day group shortened colds by 17% compared to the placebo group, twice as much as the 3/g day group. The second trial gave 4 g/day, 8/g a day, and a placebo to different groups and again saw a similar result. The 8g/day group shortened their colds by 19% when compared to the placebo group, twice as much as the 4 g/day group (University of Helsinki, 2017).

Vitamin C Saturation: Extra Ascorbic Goes Down the Drain

Despite these findings, other researchers have discovered a dose-dependent absorption and secretion of vitamin C in humans where excretion increases in proportion to blood concentration. Thus, they argue, after a saturation point, any extra vitamin C will simply be peed out (Melethil, 1986). Authorities today advise that vitamin C intake above 400 mg/day are excreted in the urine and doses above 2,000 mg can cause abdominal pain, nausea, and diarrhea (Harvard Health, 2017).

Science Says More Vitamin C is a Good Investment in Human Health

When considering Pauling’s basic observations about humans versus other animals and primates in regards to vitamin C needs, the results of animal studies showing a protective benefit of vitamin C against pathogens across species, and the results of dozens of human trials, it is hard to deny that a relationship exists between vitamin C consumption and the manifestation of viruses such as the human cold. Whether or not vitamin C can completely prevent a cold remains a subject of debate, yet there is clear evidence that it can be effective at shortening the duration of and reducing symptoms of colds. The evidence suggests vitamin C may be a useful therapeutic agent for potentially preventing, and for helping to minimize suffering associated with colds. Even if Pauling may have unknowingly exaggerated claims about vitamin C along with his recommended dosage, his research and insights have no doubt helped spur other scientists to further research this essential vitamin. Today the body of research surrounding the vitamin C debate continues growing along with the evidence suggesting more vitamin C every day may be a wise investment for human health.

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1. British Medical Journal. “Editorial: Vitamin C and the Common Cold.” Bmj, vol. 1, no. 6010, 1976, pp. 606–607., doi:10.1136/bmj.1.6010.606. 
2. Counsel for Responsible Nutrition (CRN). “Dietary Supplement Use Reaches All Time High.” CRN, September 30, 2019, https://www.crnusa.org/newsroom/dietary-supplement-use-reaches-all-time-high.
3. Harvard Health. “Can Vitamin C Prevent a Cold?” Harvard Health,  January 2017, www.health.harvard.edu/cold-and-flu/can-vitamin-c-prevent-a-cold. 
4. Hemilä, Harri, and Elizabeth Chalker. “Vitamin C for Preventing and Treating the Common Cold.” Cochrane Database of Systematic Reviews, 2013, doi:10.1002/14651858.cd000980.pub4. 
5. Melethil, Srikumaran, et al. “Dose-Dependent Absorption and Excretion of Vitamin C in Humans.” International Journal of Pharmaceutics, vol. 31, no. 1-2, 1986, pp. 83–89., doi:10.1016/0378-5173(86)90216-4. 
6. Pauling, L. Lecture by Linus Pauling, Dr. Linus Pauling and Vitamin C, Dr. Farrah Agustin-Bunch, M.D., 11 Apr. 2019, youtu.be/seBqb-NeK9o. 
7. University of Helsinki. “Larger Doses of Vitamin C May Lead to a Greater Reduction in Common Cold Duration.” ScienceDaily, ScienceDaily, 30 Mar. 2017, www.sciencedaily.com/releases/2017/03/170330115246.htm. 
8. Wilson, C W. “Vitamin C and the Common Cold.” Bmj, vol. 1, no. 5750, 1971, pp. 669–669., doi:10.1136/bmj.1.5750.669. 

Reya Steele Andrews

Reya (Steele) Andrews is a holistic health writer, educator, and publisher at Healing With Plants. Reya is a certified Holistic Nutritionist (AFPA), is certified in Plant-based Nutrition, and teaches nutrition science and healthy food preparation. Find her book, The Frugivore Diet, on Amazon.

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