This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute.

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According to Science magazine, vitamin C is coming back—but not all the way. Once this nutritional necessity was hailed as a help against ailments from cancer to the common cold. Later research disagreed. It did little or nothing for such diseases.

Vitamin C’s prowess seemed logical; it is a good antioxidant, and much of what ails us stems from the chemical action of substances that oxidize fats, proteins, and even DNA itself. (Considered from a cell’s perspective, it’s like reinforcing steel rusting away within a concrete bridge—the trouble comes from oxygen getting in where it doesn’t belong and changing a structural component into something entirely different.) Vitamin C reduces many of those chemicals before they can do their oxidizing.

So it should be good for health, and evidently it isn’t bad, even in very high doses. Consumed in amounts up to hundreds of times the recommended daily allowance, vitamin C apparently has no harmful effects (unlike other vitamins—vitamin A, for example, is notoriously toxic when one takes too much of it). Though most mammals manufacture adequate vitamin C within their own bodies, humans have lost that ability. But we need it: we have to drink it or eat it, or we develop scurvy and eventually die wretchedly. The question is only whether extra vitamin C goes beyond nutritional benefits and offers medical ones.

Vitamin C had a distinguished patron advocatingits use. Linus Pauling, a distinguished chemist and Nobel laureate, did much to popularize vitamin C’s therapeutic benefits. Pauling advocated big doses, up to 300 times the daily amount deemed necessary by dieticians, for helping stave off disease. He backed theory with experiment. For example, by means of a study made in cooperation with a Scottish physician, Pauling believed he had demonstrated that cancer patients lived longer with the help of megadoses of vitamin C.

Yet other trials, performed with the careful protocols of medical researchers, found vitamin C had no positive effects at all on patients with similar cancers. A Canadian study even disproved Pauling’s pet hypothesis that vitamin C prevented colds.

What’s always interested me about Pauling’s part in the vitamin C fracas is why his results are so different from those obtained by medical researchers. Here I’m speculating—I’ve never seen it discussed in the scientific literature—but I suspect it’s because humans make lousy test tubes.

Consider: If chemists discover a way of combining two substances to make a new compound, they test their discovery by repeating the process. They identify details like effective temperatures or whether adding substance A to B produces something different from adding B to A. They publish the results, and shortly their work will be tested by others who repeat the experiments to see if they get the same results.

But chemists don’t have to worry about how the test tubes feel about the experiment, or about how they feel about the test tubes, or the substances going into them. But feelings do affect medical experiments on human beings. Patients who think something will make them feel better are likely to feel better in actuality. Even if their doctors think they’re taking strong medicine, that alone may make them feel more healthy. So the best medical experiments are double-blind—neither the doctor nor the patient knows if the trial therapy is real or an inert look-alike.

However Pauling went astray, his determination has helped keep research on vitamin C alive. His studies may not be respectable, but his pet vitamin is finding use in cancer treatment—to counteract the toxic side effects of some of the potent anticancer drugs. It also may help prevent atherosclerosis, by blocking the oxidizing agents that turn low-density lipoproteins into fatty plaques adhering to arterial walls.

So, at the present state of knowledge, it looks as if vitamin C is a helpful agent, if not a healing one. And it will cure scurvy—but not the common cold.

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