Vitamin C and the common cold. You would think that the exact link would be clear by now. After all, it’s been more than three decades since Linus Pauling suggested that vitamin C was
the answer to this viral misery, and his theory spurred a host of investigations. Had this claim been made by anyone else, the scientific community would have yawned and ignored it. But this was Linus Pauling, a Nobel Prize winner, and perhaps the greatest chemist of the twentieth century. He had contributed so much to our understanding of the chemical bond, the structure of proteins, and the mystery of sickle-cell anemia that many scientists thought his “gut feeling” about vitamin C merited further examination.
Humans are one of just a few species incapable of synthesiz- ing vitamin C, a distinction we share with other primates, guinea pigs, fruit-eating bats, and the red-vented bulbul, a curious bird. Pauling believed that we lost the ability to manu- facture the vitamin from components in food somewhere along the evolutionary line, and that we were now paying the pen- alty. Pauling maintained that the amounts ingested in the diet may be enough to protect us from scurvy, the classic disease brought on by vitamin C deficiency, but that this was not enough for optimal health.
Linus Pauling was one of my chemical heroes when I was growing up, and I remember the excitement I felt the first time I heard him speak at a conference. It was in the early 1970s, and I can still vividly recall the great man strutting around the stage, brandishing a vial holding the amount of vitamin C a goat produces in a day, telling the enraptured audience, “I would trust the biochemistry of a goat over the advice of a doctor.” Hmmmm, I thought, that didn’t sound very scientific. But this was Linus Pauling. He had to know what he was talk- ing about!
Well, it seems that far more distinguished members of the scientific community than me weren’t quite so sure, and decided to put the vitamin C hypothesis to a test. Let’s mount some clinical trials, they proposed, and check this out. And how
appropriate that was! After all, the first real clinical trial in his- tory involved vitamin C. That goes back all the way to 1747, and the pioneering work of a Scottish ship’s surgeon, Dr. James Lind, who is usually credited with having discovered that scurvy, a disease that rotted gums, caused joints to become swollen, robbed the body of energy, and often killed its victims, could be cured with citrus fruit juice. Actually, others had made similar observations before Dr. Lind. When Jacques Cartier’s ships became icebound in Quebec in 1536, only three of his 100 men escaped the ravages of the disease. It was then that the native Stadacona people came to his rescue and advised the men to make a tea by boiling the leaves of a tree, probably the white cedar. Rapid recovery was observed after only a couple of doses, but due to poor information transmission in those days, the remedy seems to have been lost. There were other instances of effective scurvy treatment. In the seventeenth century, some East India Company ships carried supplies of lemon juice to ward off the disease. Still, these were isolated cases, and thou- sands of sailors elsewhere perished from scurvy.
That’s when Lind entered the picture. He had undoubtedly heard accounts of treating scurvy with various foods or bever- ages, and he decided to get to the bottom of the matter. Aboard the hms Salisbury, he selected six pairs of men, and gave them either a daily dose of cider, dilute sulfuric acid, vinegar, seawater, a mish-mash of garlic, mustard seed, and radish root, or two oranges and a lemon. There was also a control group of men with scurvy who got the regular ship’s rations. Within days, the two men who were lucky enough to have been put on the citrus diet began to recover. So although Lind was not the first to discover a treatment for scurvy, he certainly was the first to document a “clinical trial” showing the effectiveness of the citrus remedy, which he did in his “Treatise on Scurvy” in 1753.
Still, it wasn’t until 1795 that the British navy began to provide a daily supply of lime or lemon juice to all its men.
Dr. Lind would have approved of the clinical trials that various researchers organized to check out Pauling’s vitamin C–common cold hypothesis. Over sixty controlled studies have examined the effects of vitamin C supplements on the common cold, in some cases using up to several grams a day. You can pick and choose among these studies to “prove” what- ever point you want to make. If you want to show no effect whatsoever, an Australian study of 400 volunteers taking vari- ous doses of vitamin C over eighteen months is the example of choice. If you want the opposite result, check out an American study of 463 students over two years. And if you want the true bottom line, here it is. The evidence that vitamin C supple- ments can prevent the common cold is very sketchy, although there may be an effect in people who have an extremely low dietary intake of the vitamin.
This is corroborated by the findings of two researchers, one Australian, the other Finnish, who examined the published studies to date and subjected them to critical analysis. They looked at some fifty-five placebo-controlled trials that used at least 200 milligrams of vitamin C supplements a day. The results are not spectacular. In people who took vitamin C regularly to prevent colds, there were no fewer colds, but there was a slight reduction in the number of days they experienced symptoms: 14 percent for children; 8 percent for adults. Interestingly, there was a 50 percent reduction in the incidence of colds in marathon runners, skiers, and soldiers exposed to significant cold and or physical stress. There was also some evidence that taking large doses of vitamin C, as much as 8 grams, on the day that cold symptoms appear can shorten the duration of a cold. Indeed, a recent study showed that the synthesis of cytokines, chemicals
the body generates to fight viruses, is increased within hours of taking a gram of vitamin C.
Taking vitamin C prior to extreme physical exertion or exposure to cold stress therefore makes sense, as does taking large doses the first day that cold symptoms appear. In any case, the impact of vitamin C supplements on the common cold is not a major one. If it were, we would have seen it conclu- sively in the studies, and we would not be debating the issue.