Carbohydrate-Induced Lipemia

Pete Ahrens of Rockefellar University was considered by many investigators to be the single best scientist in the field of lipid metabolism. He observed how the triglyceride levels of some patients go up on low-fat diets and they fall on high fat diets. Ahrens called this carbohydrate-induced lipemia (an excessive concentration of fat in the blood). He gave lectures where he showed two photos of blood serum obtained in a test tube from the same patient. One photo was taken during the low-fat, high-carbohydrate diet, and the other was taken during the high-fat, low-carbohydrate diet. One test tube was perfectly clear and the other was milky white, indicating the lipemia. The surprise was that the lipemia occurred during the high-carbohydrate diet and the clear liquid happened during the high-fat diet. Elliott Joslin reported this phenomenon in diabetics thirty years earlier.

Over the course of two decades, Ahrens only saw two patients whose blood serum became cloudy with triglycerides after eating high-fat meals. He had thirteen in whom carbohydrates caused the lipemia. Since Very Low Density Lipoproteins(VLDL) particles that carry triglycerides, also carry cholesterol, they contribute to the total cholesterol. This means that when a person has high triglycerides their cholesterol will be elevated as well. This prompted Ahrens to believe that high cholesterol was an exaggerated form of the normal biochemical process which occurs in all people on high-carbohydrate diets.” He acknowledged that it was also possible that a genetic disorder might explain the observations.

Either way, the lipemia would clear up on a low-calorie diet. This would explain why the carbohydrate-induced increase in triglycerides was absent in Asian populations living primarily on rice. The majority of Asian populations ate at a bare subsistence level. They ate low-calorie diets compared with their level of physical activity, and this combination would counteract the triglyceride rising effect of the carbohydrates, according to Ahrens. The critical question was whether prolonged exposure to abnormally high triglyceride levels increased the risk of atherosclerosis. In other words, does eating too many carbohydrates lead to high triglycerides, which leads to heart disease?

John Peters was the chief of the metabolic division at the Department of Medicine at Yale University. He was renowned in the medical community for his measurements of the chemical constituents of body fluids. He used an analytical centrifuge, which was a less sophisticated version of the one John Gofman used for the atomic bomb, and for his calculations concerning cholesterol which four teams were unable to master. Peters suggested that this device be used to test the association between high triglycerides and heart disease. Peters died in 1955, but Margaret Albrink, Wister Meigs, and Evelyn Man continued the work. They compared triglyceride and cholesterol levels from patients at New Haven Hospital with those of healthy employees at American Steel and Wire. They found that elevated triglycerides were far more common in coronary heart-disease patients than high cholesterol. In fact, only 5 percent of the healthy young men had elevated triglycerides compared with 38 percent of healthy middle-aged men and 82 percent of coronary patients.

At about the same time that the American Heart Association embraced Ancel Key’s hypothesis of cholesterol and heart disease, both Ahrens and Albrink presented their research at a meeting of the Association of American Physicians in Atlantic City New Jersey. The New York Times covered the talk and their headline read, “Rockefellar Institute Report Challenges Belief that Fat is Major Factor.” However, the story was buried deep in the paper. Gary Taubes reported that people were so angry that they couldn’t believe what was being reported. Proponents of Key’s hypothesis were vehement and attacked them relentlessly.

Despite the attacks, the results were independently confirmed by Peter Kuo of the University of Pennsylvania; by Lars Carlson of the Karolinska Institute in Stockholm, and by the future Nobel laureate Joseph Goldstein and his colleagues from the University of Washington. All three reported that high triglycerides were considerably more common in heart-disease victims than was high cholesterol. In 1967, Kuo reported in the Journal of the American Medical Association that he studied 286 atherosclerosis patients. Physicians who thought their patients had the genetic form of high cholesterol referred 246 patients. This turn out to be true in only 10 percent of the patients. The other 90 percent had carbohydrate-induced lipemia and for most of these patients their sensitivity to carbohydrates elevated their triglyceride and cholesterol levels. When Kuo put these patients on a sugar-free diet, he reported that their triglyceride and cholesterol levels lowered with only five to six hundred calories of starches per day. Two months later, the JAMA published an editorial in response to Kuo’s article suggesting that the

“almost embarrassingly high number of researchers who boarded the ‘cholesterol bandwagon’ had done a disservice to the field. This fervent embrace of cholesterol to the exclusion of other biochemical alterations resulted in a narrow scope of study. Fortunately, other fruitful approaches have been made possible in the past few years by identification of the fundamental role of such factors as triglycerides and carbohydrate metabolism in atherogensis.”

Despite this conclusive evidence, measuring triglycerides was still much more difficult than measuring cholesterol and so only the rare laboratory had the facilities to do it. The National Institutes of Health was the only effective funding source for research of this nature in the US. At this time, their resources were already committed to three enormous studies, the Framingham Heart Study, Key’s Seven Countries Study, and the pilot programs of the National Diet-Heart Study. These studies would only measure cholesterol. This means they only tested Keys’s hypothesis. No consideration was given to any alternative hypothesis. By 1961, Keys and his collaborators had already tested over ten thousand men. By 1963, they completed exams on another eighteen hundred men. Even if it were technically possible to go back and include triglycerides in the measurements the cost would have been astronomical. Therefore, the fat-cholesterol hypothesis came out ahead.

The history is unambiguous and not uncontroversial. The choice is yours.