BMJ  2004;328 (24 January), doi:10.1136/bmj.328.7433.0-g

Editor's choice

"Let food be thy medicine..."

Mark Lucock ends his review of the science of folic acid by quoting Hippocrates: "Let food be thy medicine and medicine be thy food" (p 211). Although many patients are convinced of the importance of food in both causing and relieving their problems, many doctors' knowledge of nutrition is rudimentary. Most feel much more comfortable with drugs than foods, and the "food as medicine" philosophy of Hippocrates has been largely neglected. That may be about to change. Concern about obesity is rocketing up political agendas, and a growing interest in the science of functional foods is opening up many therapeutic possibilities (p 180).

It was in 1931 that Lucy Wills described how yeast extract could be effective in preventing tropical macrocytic anaemia of late pregnancy. Folate was shown to be the crucial factor. In the 1980s a series of studies showed how periconceptional folate could prevent spina bifida. Then in 1995 came a meta-analysis that established that high homocysteine concentrations were a risk factor for atherosclerosis. Dietary folate reduces homocysteine, raising the possibility that a vitamin might prevent vascular disease. Next, several nucleotide polymorphisms were found to be related to folate, meaning that folate levels might influence the chance of developing cancer.

These discoveries are not surprising as folate metabolism is involved in many of the fundamental processes of life. Lucock describes, for example, how it is important for nucleotide biosynthesis. Thymidylate synthase, an enzyme that helps synthesise DNA, depends on a folate derivative. Low levels of folate may thus lead to breaks in DNA, predisposing to cancer. There are many other ways in which folate can affect gene function, and so folate is central to nutrigenomics—the study of the links between nutrition and gene function.

Folate may thus be a leading contender for panacea of the 21st century. Addition of folate to foods might reduce birth defects, vascular disease, and heart disease—and the Americans favour fortifying bread with folate. But folate being involved in so many of life's fundamental processes not only leads to its possibilities as a panacea but also to the prospect that "messing around with folate" could do extensive harm. The folate used in food fortification is not a natural co-enzyme, and nobody knows the long term effects of exposing whole populations to the unnatural folate.

There is thus great potential for good, some possibility of harm, and much uncertainty. The question of fortifying foods inevitably becomes highly political, and the politics of nutrition are just as complex as the science. Owen Dyer tells how the United States government—lobbied by food manufacturers—is trying to undermine a report by the World Health Organization on Diet, Nutrition, and the Prevention of Chronic Disease (p 185). My unadventurous prediction is that we will be hearing much more about the science, medicine, and politics of food. Hippocrates would be pleased.

(rsmith{at}bmj.com)

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