Fat,children&chronic disease - EFR 6-15

This article on the relationship of fat in the diet to chronic disease is a good example of why we need to continue to get people to better understand how statistics are used. Alfred Harper demonstrates that just because two things increase together (like fat and heart disease) does not permit us to automatically conclude that one thing "causes" the other. In this case a third element (an aging population) also becomes a factor.

Excerpted from FOOD CHEMICAL NEWS, pages 25-27, January 22, 1996

Low-fat diets are not appropriate for children or the elderly, according to Alfred Harper, a professor emeritus of biochemistry and natural sciences at the University of Wisconsin. Professor Harper spoke at the Jan. 16-17 Southern California Food Industry Conference in Costa Mesa, Calif. His information is also reported in the April, 1996 supplement to the Journal of Nutrition (pp. 1042S-1048S).

Diets containing almost no fat are not a cure-all according to Harper and John Allred, a professor of nutrition at Ohio State University. They suggested that low-fat food might even, inadvertently, be making people fatter.

As to relating fat to chronic disease, Harper argues that the rise in cancers and cardiovascular disease is a natural consequence of an aging population. "The claim that coronary heart disease mortality increased in association with increases in the saturated fatty acid and cholesterol content of the U.S. food supply is a 20th century myth," Harper declared.

"This did not occur because either diets or health had deteriorated. It occurred because the proportion of people 65 years of age or older had tripled and because ... death rates from chronic diseases increase exponentially with increasing age," Harper said, adding: "Eighty percent of deaths from heart disease occur among people over 66 years of age."

Harper faulted the USDA/DHHS Dietary Guidelines for Americans because they have been applied to children. "These guidelines represent a sharp change in direction in health policy and dietary guidance, away from dietary advice to ensure that growth and development of children will not be impaired and toward a program of dietetic medicine to prevent chronic and degenerative diseases," Harper said. Harper saidthe assumption that limiting fat intake in children will provide them with healthier lives as adults has not been validated by research.

In relation to fat and cardiovascular disease and cancer, Harper presented statistics which showed that when death rates are adjusted for changes over time in the proportions of people of different ages in the population, the mortality from cardiovascular diseases actually declined between 1940 and 1960 and the mortality from cancer was unchanged. The 1940-1960 period is often used to relate increased fat intake to increases in chronic disease. Dr. Harper's contention is that the population was getting older, and this accounts for the increases in chronic disease.

In driving home his point, Harper explained that the statistical categories had changed during this time, with arteriosclerotic heart disease only becoming separate in 1949 and coronary heart disease in 1965. "Between 1940 and 1968, just 28 years after the first of these categories was established, the proportion of total heart disease deaths that was attributed to coronary heart disease increased from 22% to 90%, an amazing rise," Harper said. "But, as this occurred, the proportion of total heart disease deaths that was attributed to non-coronary categories of heart disease declined from 78% to 10%. This fascinating reciprocal relationship indicates that a change had occurred in the categories to which heart disease deaths were being attributed," he said.

Harper was more heartened by the third revision of the Dietary Guidelines, released recently. Although the guidelines have changed little, Harper noted that the text has been modified considerably. "The emphasis on diet as medicine has been reduced and more emphasis has been placed on the role of nutrition and diet in the maintenance of health," he said. Also, he noted that "advice about low-fat diets for children is less rigid. Increased emphasis on the total diet and less on unique benefits of specific foods is a promising step."

"Nonetheless," Harper added, "in commentaries I have seen or heard, this has not been emphasized. With the trend toward categorizing foods as medicines or health hazards so ingrained, nutrition professionals have their work cut out for them in attempting to restore acceptance of the basic principle that health depends on the total diet, not on a few special components. This is of particular concern with the diets of children, pregnant women, older persons, and for weight control programs."

John Allred noted that Americans obsession with losing fat has not translated into weight reduction, citing an eight-pound gain of the adult American over the 10 years from 1982 to 1992. "The public got the idea that it's the fat in the diet, not the calories," said Allred, noting that many people don't realize that you can add weight by eating too much carbohydrate as well.

"I think that's what we have to talk to people about." Allred said. "The most important number on a nutrition label is serving size. If it says low fat, low calories, it's only low fat, low calories if you eat the serving size."

But nutrition educators have a tough job ahead of them, according to Allred. "I think fat in the diet has been one of those cues that we have gotten used to, that tells us we've had enough to eat. When you lower the fat in the diet, you've lost one of those cues and you have to make it up by brain power."