Beware diet panaceas
"Good food . . . should be eaten and enjoyed," advises the Food and Nutrition Board of the National Research Council, adding that such food ". . . should not be regarded as a poison, a medicine, or a talisman." So much for the waves of polyunsaturated, you-are-what-you-eat diet fads that have carried away food-conscious people in recent decades.
But while the board's report, released in late May, struck what many may consider a blow for common-sense eating, its comments on the quality of scientific research underlying diet recommendations should be considered in their own right. They highlight a problem that afflicts many areas of public policy with scientific aspects -- the tendency of advocates of various courses of action to treat partial or otherwise inadequate scientific studies as though they had produced well-established facts.
In regard to diet and health, the board criticized some widely publicized diet recommendations as being based on statistical evidence that, while it shows a coincidence between certain dietary factors and health effects, cannot demonstrate any direct cause-and-effect relationship. Recommendations to restrict eating fatty foods to control cholesterol levels in the blood fall into this category. The board warned against making major alterations in diet until there is more compelling scientific evidence to show clearly what such dietary changes, if any, would be wise.
The board's stand has already been strongly protested by groups, such as the American Heart Association, that have taken positions on dietary issues. But the fact remains that the kinds of studies on which these groups have relied are open to the criticism made by the nutritional board.
It was an ironic coincidence that this report on diet shared headlines with the controversy over the recent half-baked studies of presumed health effects at Love Canal. One of these studies investigated possible chromosomal (genetic) damage among area residents. This widely reported study found some evidence interpreted as showing such damage. However, the findings have been criticized as invalid because no control group (a comparison group of people not in the canal area) had been used, and for other statistical defects. A second study purporting to find signs of nerve damage among canal residents was also found to be statistically shaky.
The most such studies could do is show a need for further, thorough research. They are no basis for making policy or for action. Yet the fears the studies and associated publicity have raised have forced an expensive evacuation of canal residents.
Other examples of hasty public action based on an inadequate scientific basis are the ban of fluorocarbons in spray cans and the withdrawal of saccharin. In the former case, the danger to Earth's ozone layer from fluorocarbons has yet to be fully established; while in the latter, subsequent study has shown the saccharin action to have been premature.
Thus one of the most important aspects of the nutritional report is its warning not to act on the basis of inadequate scientific information. That really is only reacting to fear.
