Link Between Mayo, Heart Disease Studied

Margarine and mayonnaise have been out of favor for so long that people who abandoned them for health’s sake must have joyously cried out, “Set sail for home!” on hearing the recent news linking the two foods to lower rates of heart disease.

Let’s see if we can clarify the matter with no more bruising of their hopes than necessary.

A research team led by epidemiologist Lawrence H. Kushi of the University of Minnesota School of Public Health set out to see if vitamins A, C and E prevent coronary heart disease. Vitamins C and E, as well as the “provitamin” carotenoids from which vitamin A is made, are antioxidants, chemicals that may be able to reduce cholesterol’s potential for harm in the bloodstream.

The study was of a type scientists call epidemiological; large amounts of data are accumulated and examined for possible relationships. It began with a questionnaire answered in 1986 by 34,486 postmenopausal women who did not have cardiovascular disease. Seven years later, the health records of the women were compared with the responses they had given to the questions about their eating patterns.

The researchers concluded that the amount of vitamin A and C the women consumed, whether from food or supplements, had no effect on their risk of death from coronary heart disease. Vitamin E from supplements was also judged to have no effect.

They did conclude, however, that there was an inverse relationship between the consumption of certain foods - nuts and seeds, margarine, and mayonnaise or creamy salad dressing - and heart disease.

Women who said they ate four or more servings a week (about a tablespoon each) of margarine or four or more servings a month of nuts had only about 60 percent as many heart disease deaths as those who said they ate none. Those who said they had two or more servings a week of mayo or creamy dressing had about half as many such deaths as those who ate none.

All these foods are high in fat and in vitamin E. Through further statistical examination, the research team concluded that the healthful element in these foods was the vitamin E.

So what does it all mean?

C. Wayne Callaway, a George Washington University endocrinologist, said other interpretations of the results were possible.

First, the relationship could be “purely fortuitous,” a statistical fluke. Secondly, “as they mention but dismiss, vitamin E foods could be high in other things.” Science is only beginning to appreciate the wide range of substances in foods that may have an effect on health.

Thirdly, the results may be caused by a “threshold effect,” meaning a certain minimal amount of vitamin E might be good while additional amounts do nothing. Finally, he said, “the dietary intake of vitamin E could simply be a co-variable, something that’s associated with a healthy lifestyle rather than something that’s beneficial.”

Margo Wootan, senior scientist at the Center for Science in the Public Interest, says people need to “put one study in the context of all the existing evidence. And there’s very good consensus that consumers should limit their intake of total fat and especially saturated fat.”

The fat in vegetables, and thus in margarine and mayonnaise, is mostly unsaturated; animal fat, as in meat and butter, is primarily saturated fat.

“I think most (health organizations) would agree that mayonnaise and margarine are foods that people should eat moderate amounts of,” Wootan said. “Those are major sources of fat in Americans’ diets.”

She said it’s wise to use reduced-fat and reduced-calorie margarines and mayonnaise. “And we recommend with margarines that you choose a light margarine rather than full-fat, and that you choose a tub rather than a stick,” Wootan said. “In general, the softer the fat, the less heart-unhealthy it is.”

Vitamin E, she said, is present in many foods. “With fruits and vegetables you may get less per serving, but by the time you eat your five to nine servings you can get quite a bit of vitamin E for the day.”

The study hardly proves that you should eat more margarine and mayonnaise, Callaway said. But consumed in moderation, on the other hand, they’re nothing to worry about.

“Stop the good-food, bad-food nonsense and start talking about the overall diet,” he said. “Eat fruits and vegetables, eat a variety of foods and exercise.”