Unsaturated Fat: The First Dietary Intervention to Lower Plasma Cholesterol
Ahrens, Jr., Edward
Courtesy of the Rockefeller Archive Center
Today it is common knowledge that high cholesterol levels raise the risk of heart disease, and people trying to lower their cholesterol are advised to avoid foods high in saturated fat. This advice derives directly from the discoveries of Edward H. Ahrens (1915-2000). In the 1950s, he was the first to carry out careful dietary studies proving that the kinds of fats people eat alter levels of cholesterol in the blood. In particular, he found that replacing saturated fat in the diet with unsaturated fat lowers serum cholesterol.
These important discoveries depended on the study of human subjects in the Rockefeller Hospital as well as newly developed techniques for separating and analyzing lipids. For periods of time ranging from four months to three years, Ahrens' patients were fed a precisely chemically defined liquid diet while their serum lipids were monitored. With this formula diet, Ahrens could vary the type of fat included—he tested corn oil, beef tallow, lard, and olive oil, among others. Combining formula diets with modern analytic methods, he was able to show the importance of fatty acid unsaturation and chain length in determining serum lipid levels.
Continuing studies with patients over the next decade and longer led Ahrens to uncover the mechanisms of cholesterol metabolism. The body manufactures its own cholesterol, and Ahrens devised a technique, known as the sterol balance method, for determining daily cholesterol production by measuring the difference between dietary intake and total daily excretion. In the process, he discovered the wide variation among individual people in how they metabolize cholesterol.
Road map of cholesterol metabolism. Illustration by Holly Johnson
Edward H. Ahrens, Jr., received the BS (1937) and the MD (1941) from Harvard University. He joined the Rockefeller Institute in 1946 and was appointed professor in 1960. In 1982 he became the University's first Frederick Henry Leonhardt Professor. Ahrens was elected to the U.S. National Academy of Sciences, and he founded the Journal of Lipid Research. Throughout his career Ahrens advocated for patient-oriented research, and was known for his 1992 book, The Crisis in Clinical Research, which examined how medical science had moved toward laboratory research. The Association for Patient-Oriented Research gives an annual award in his name, the E.H. Ahrens, Jr. Award for Clinical Research.
Ahrens EH Jr, Blankenhorn DH, and Tsaltas TT. Effect on human serum lipids of substituting plant for animal fat in diet. Proc Soc Exp Biol Med, 1954, 86: 872-878
Ahrens EH Jr, Hirsch J, Insull W Jr, Tsaltas TT, Blomstrand R, and Peterson ML. The influence of dietary fats on serum lipid levels in man. Lancet, 1957, 1: 943-953
Ahrens EH Jr, Hirsch J, Insull W Jr, Tsaltas TT, Blomstrand R, and Peterson ML. Dietary control of serum lipids in relation to atherosclerosis. JAMA, 1957, 164:1905-1911
Ahrens EH Jr. After 40 years of cholesterol-watching. J Lipid Res, 1984, 25: 1442-1449
Hirsch J. A tribute to Pete Ahrens. J Lipid Res, 2001, 42: 891-893
Rockefeller Archive Center, papers of Edward H. Ahrens, Jr.