Alexander Leaf, a versatile physician and research scientist who was an early advocate of diet and exercise to prevent heart disease, and who traveled the world to make important discoveries about increasing human longevity and to help scientifically establish the dangers global warming poses to the human species, died on Dec. 24 in Boston. He was 92.
The cause was complications of Parkinson's disease, said his wife, Barbara Leaf.
Dr. Leaf's career toggled between pure scientific research and medical practice; unusually for the medical world, he sustained achievement in both realms. He was at different times chairman of medicine and chief of medical services at Massachusetts General Hospital in Boston, one of the nation's premier hospitals, and led the department of preventive medicine at Harvard Medical School. He was one of the first practicing physicians ever elected to the National Academy of Sciences, in 1972.
He was probably best known for his work on heart disease, advocating prevention through exercise and diet, particularly foods low in animal fat and sodium.
Dr. Leaf's research into the cellular biology of heart disease led him to undertake a series of expeditions in the early 1970s to study longevity in parts of the world where heart disease was rare and some people were said to live 140 years or more.
The expeditions, sponsored by the National Geographic Society, were criticized when some of the very old people in the study turned out to have lied or been misinformed about their ages. Dr. Leaf openly disavowed the project. But he never doubted the basic insights he had gleaned from the scores of interviews he conducted with people in the Caucasus Mountains, the Hunza Valley of Pakistan and the foothills of the Andes.
Whether they were 120 or older, as many of the subjects had claimed, or in their late 90s, as was later found, he concluded that people who lived in mountainous places, worked outdoors into their old age and consumed local food high in vegetable content and low in animal fat tended to live very long and healthy lives free of heart disease.
Dr. Leaf made a similar series of trips in the late 1980s, sponsored by the World Health Organization, to study the effects of climate change in Africa. His report on the study was published in The New England Journal of Medicine in 1989, drawing praise from public health experts as one of the first to link longer, hotter summers with outbreaks of infectious diseases like malaria in regions previously untouched by them.
Dr. Arnold S. Relman, a professor emeritus at Harvard Medical School and former editor in chief of The New England Journal, said Dr. Leaf "had a moral sense that science was not just for answering basic questions about the human body, but for dealing with the broader questions of human suffering and human welfare."
Dr. Leaf was born Alexander Livshiz on April 10, 1920, in Yokohama, Japan, where his Russian-born parents had separately fled during the Russian civil war after the Bolshevik Revolution. His parents, both dentists, changed the family name when they arrived in Seattle in 1922.
He graduated from the University of Washington as a chemistry major, received his medical degree at the University of Michigan and served his internship and residency at Massachusetts General.
Besides Mrs. Leaf, whom he met while both were students at the University of Washington, his survivors include their daughters, Caroline, Rebecca and Tamara Leaf, and two grandchildren.
Dr. Leaf's early research focused on how sodium and potassium pass through cell walls, a process crucial to cellular health and important in understanding the causes of heart disease. His work on toad bladders was considered seminal in the development of treatments for life-threatening heart arrhythmias.
As chief of medical services at Massachusetts General from 1966 to 1981, he established one of the first programs in the country for primary-care medical residents and set up a network of free clinics in poor neighborhoods around Boston. He was a founding member of Physicians for Social Responsibility, which was formed in 1961 to oppose nuclear proliferation and later added environmental and social problems to its portfolio. He led Harvard's department of preventive medicine from 1981 to 1990.
Dr. Leaf continued his research after retiring from teaching, remaining active almost as long as the mountain-dwelling subjects of his 1970s studies.
In his 80s he began studying the effects of fish oil and fatty acids on longevity. In 2005 he was the lead author of a paper published in Circulation, the journal of the American Heart Association, describing the effectiveness of fish oil's omega-3 fatty acids in reducing heart attacks triggered by ventricular arrhythmias, which are chaotic contractions of the heart muscles.
"There is still some uncertainty about the extent of the benefit," Dr. Relman said, "but I dare say if you ask most cardiologists, they will tell you that as a result of that article they are taking daily doses of fish oil, myself included."
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