Vitamin C does nothing to prevent or reduce the severity of colds.

by Brian Dunning

Filed under Alternative Medicine, Consumer Ripoffs

Skeptoid Podcast #103

June 3, 2008

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Also available in Russian

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https://skeptoid.com/audio/skeptoid-4103.mp3

What do you do when someone in your household catches a cold? If you're like me, you run for the medicine cabinet and start megadosing yourself with vitamin C. Everyone knows this is the best way to stave off a cold. Everyone also seems to think that vitamins are like spinach for Popeye: Whether you need them or not, taking extra vitamins when you don't necessarily have a deficiency is perceived to bestow some sort of super-health, as if you can somehow be even healthier than healthy. If you take any vitamin supplement, and you do not have a diagnosed vitamin deficiency, please listen carefully to the following.

The idea that vitamin C is a wonder drug for preventing colds and other illnesses became widely popular around 1970, due largely to some books written by one of our greatest scientists, Linus Pauling. Along with Marie Curie, Pauling shares the distinction of being one of only two people to receive Nobel Prizes in two different fields. He received his first in chemistry in 1954 for his pioneering work characterizing the nature of chemical bonds. He received the Peace Prize in 1962 for his work warning of the dangers of nuclear weapons proliferation and radioactive fallout. Ironically, it was this type of activism that had almost prevented his being able to travel to Stockholm to accept his first prize: In those days, the United States was in the habit of denying passports to citizens who were sufficiently outspoken against nuclear weapons. Pauling's contributions to 20th century science are inestimable. He described the structure of the atomic nucleus. He was a key player in the theorized, and later proven, helical structure of DNA. He was practically the founding father of the whole science of molecular biology. He was even involved in the development of one of the first commercially available electric cars, the 1959 Henney Kilowatt.

So how is it possible that such an accomplished genius could be fundamentally wrong for much of his career? Let's set aside the notion that a scientifically brilliant mind must always be a rational, objective, and unbiased mind, and look at Pauling's later writings. In 1970, he published a book called Vitamin C and the Common Cold, in which he outlined the concept he called orthomolecular medicine. Orthomolecular means the "right molecule". Its central thesis is that megadoses of vitamin C prevent colds and can prevent or treat other conditions. He expanded this to include cancer when he wrote 1979's Vitamin C and Cancer. In 1986 he published How to Feel Better and Live Longer, in which he broadened all his concepts and claimed that megadoses of all vitamins would improve your overall health, would slow aging, and increase your enjoyment of life. It's important to note that orthomolecular medicine is not a concept shared by responsible doctors or dietitians; it is squarely in the alternative medicine camp. The Mayo Clinic tested Pauling's claims about treating cancer with vitamin C in three different randomized controlled trials, all of which showed no beneficial effect. Pauling spent years passionately trying in vain to discredit these trials, which created something of a gap between himself and mainstream medical science. In fact, despite the staggering importance of his earlier contributions to science, by the end of his life Dr. Pauling was largely regarded as a crank by his former colleagues, much like Nikola Tesla, by some accounts.

There have been at least 30 well-performed controlled trials to find out whether vitamin C at various dosages can prevent colds, or reduce their severity. What these studies have determined is that vitamin C has no preventive value at all; you're just as likely to catch a cold if you take daily megadoses as you are if you take nothing at all. A few of these trials did find small reductions in the severity or duration of the colds, but most trials did not show even this small effect.

I know all of this, but every time the cold and flu season comes around, I still catch myself eyeing that vitamin C bottle. I'm like the jungle native who's been baptised by the missionaries, but whenever the volcano erupts, I still run to the stone pagan idol. My own experience is that I've never gotten sick whenever I've been regularly taking vitamin C. And, this is the same experience reported by a lot of people. So it would seem that our own experiences support what Dr. Pauling was saying, and disputes what testing has revealed. We all have to believe our own eyes, and to believe our own first-hand experiences, right?

Well, yes, but we also have to understand the way our brain interprets our experiences. Practically the whole reason for the science of psychology is that what we think and feel is not necessarily 100% translated to the real world. It's certainly possible to misinterpret something someone tells us, so isn't it also possible to misinterpret other experiences? Well, we do misinterpret our own perceptions and our own experiences, and we all do it every day. Is it possible that you did have a minor cold, but since you were taking vitamin C the thought never entered your mind that it could be a cold? Maybe you just attributed it to seasonal allergies, and even though the facts are that you got a cold while taking vitamin C, your own perception confirms that the vitamin C was 100% effective. Is it possible that you don't exactly remember the number of colds you got last year? Of course it is. And, perceptual biases aside, is there any chance that you wouldn't have happened to catch a cold anyway? Of course that's possible too.

Thus, you can't reasonably consider your own experience as evidence that vitamin C is effective against colds. Your only evidence is anecdotal and unreliable due to a variety of perceptual phenomena; and in any case your own test of vitamin C was an uncontrolled, unblinded test with no statistical validity.

But you're not alone. A lot of people believe that vitamins will prevent colds, and the alternative medicine industry has always been quick to capitalize on this. There's a product called Airborne that is a repackaging of an ancient Chinese remedy called yin chiao. It contains undisclosed quantities of a few herbs and vitamins, including vitamins A, C, and E. Their marketing slogan is "Invented by a schoolteacher", which for some reason people view as meritorious, even though all it really means is "Invented by someone with no medical background whatsoever". For a decade they made false advertising claims that their product could prevent and treat colds. Sure enough, eventually the law caught up with them, and fined them $23 million and ordered them to refund the purchase of anyone who ever bought their product. They're still in business, although they now make the claim that Airborne boosts your immune system. As any doctor will tell you, "immune system boosting" is pure pseudoscience. It's medically meaningless, but that's a whole other subject that we'll examine in a future episode.

Not only is there a lack of evidence that these products have any beneficial effects, there is well established evidence that they can be dangerous. If you take the recommended dose of Airborne to fight a cold, you're taking enough of a vitamin C overdose to put yourself at risk of kidney stones. Although the popular folk wisdom teaches that extra vitamins are simply excreted in the urine, this is largely untrue. Vitamin overdosing is called hypervitaminosis or vitamin toxicity, and can lead to serious effects. Hypervitaminosis A can lead to birth defects, liver problems, osteoporosis, skin problems, and hair loss. Hypervitaminosis D can cause dehydration, vomiting, anorexia, hypercalcemia and kidney damage including kidney stones. Hypervitaminosis E can lead to blood problems including high cholesterol and can act as an anticoagulant. It should be noted that to be at risk of any of these conditions, you would need to significantly overdose over a long period of time. Brief or modest overdoses of any vitamin supplement are unlikely to cause problems. Interestingly, vitamin K is an effective treatment for many hypervitaminosis toxicity conditions.

A common criticism I receive is "Why should I believe you, when upstanding companies like Airborne, and practically everyone else in the world, tells me I should take vitamins?" Well, I hope you don't trust me. I hope that if you're truly interested, you'll ask a medical doctor. And by "doctor" I don't mean a naturopath, a health food store clerk, or anyone else who's in the business of selling you vitamin supplements. The simple fact is that nearly everyone who eats anything close to a balanced diet in any developed country is extremely unlikely to have a vitamin deficiency. Thus, there is no plausible benefit to vitamin supplementation for general health or wellness.



By Brian Dunning

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