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Nutrition Researcher Frank Hu: Fat Quality More Important Than Quantity
Frank Hu, research associate in the Department of Nutrition, has been receiving a lot of attention lately from the popular media. The reason for this attention is that he has
been lead author of a number of studies that have produced good news about a popular and necessary activity: eating
Specifically, his work has examined the relationship between diet and heart disease. In November, 1998, Hu reported in the British Medical Journal that eating nuts reduced the risk of coronary heart disease in women. In April, his paper in the Journal of the American Medical Society showed that there was no link between moderate egg consumption and heart disease. Most recently, in the May issue of the American Journal of Clinical Nutrition, his analysis demonstrates that linolenic acid, an omega-3 fatty acid found in some vegetable oils and salad dressing products, may protect against fatal heart attacks.
Hu's work has comprised a series of collaborations with Walter Willett, Fredrick John Stare professor of epidemiology and nutrition, and other colleagues in the Nurses Health Study and the Health Professionals Follow-up Study. This same group, in 1997, published an article in the New England Journal of Medicine indicating that total fat consumption was less important to heart disease than the type of fat consumption.
"The problem is that 'total fat' is not a useful term," said Hu. "There are good fats and bad fats. In the public's mind, fat has become public enemy number one. Reducing dietary fat has become a priority. But the truth is that if you reduce your total fat consumption, you're also reducing the amount of good fats that you eat--fats that have a protective effect against heart disease."
Bad fats are those that are frequently found in dairy, meat, and other animal products. These are saturated fats that have been shown to increase levels of low-density-lipoprotein (LDL) cholesterol in the bloodstream. If the body has more LDL cholesterol than it requires, the excess is deposited on the walls of arteries in the form of plaque. Too much plaque and the arteries become plugged--a condition known as arteriosclerosis. When arteries in the heart become clogged, it causes a heart attack. If arteries that lead to the brain are plugged, then the result is a stroke.
Good fats, on the other hand, are found in liquid vegetable oils. These include monounsaturated fats and polyunsaturated fats. These fats lower LDL cholesterol levels, resulting in lower risk of cardiovascular disease.
Trans fats muddy the waters. "Trans fats are vegetable oils that are partially hydrogenated," explained Hu. "Adding hydrogen to the oils makes them solid at room temperature, a characteristic that makes them useful in the production of baked goods. Products made with hydrogenated oils have long shelf lives. "Unfortunately, trans fats are more dangerous than saturated fats. Not only do trans fats increase LDL cholesterol levels like unsaturated fats, they also reduce levels of HDL cholesterol--the helpful cholesterol. Trans fats do double harm."
Explicating the relationships between types of fat and risk of heart disease has been the basis of Hu's recent work. "We did the nut study to prove our point. Many people avoid nuts because they're notoriously high in fats--up to 80% of the energy in a nut comes from its fat content. Therefore, many people assumed that eating nuts would increase risk of heart disease. But, because nuts contain primarily unsaturated fats, eating nuts substantially reduces risk of heart disease."
Next, Hu and his colleagues turned to eggs: "Eggs have been perceived as unhealthy food for many years because of their high cholesterol content. People have assumed that egg consumption would lead to increased risk of heart disease."
Hu was not surprised by the results of the study. "Moderate egg consumption, which we defined as one egg per day, is not associated with increased risk of heart disease. These results are consistent with data from previous metabolic studies that suggested relatively small effects of dietary cholesterol on cholesterol levels in the bloodstream," he said. "The slight adverse effect of an egg's cholesterol content is balanced by the beneficial contents of its other nutrients."
The researchers did find, however, that egg consumption is dangerous for people with diabetes, possibly because of their altered ability to metabolize cholesterol. Moderate egg consumption led to a 40-to-50% increased risk of heart disease for diabetics.
Hu's next project is an examination of the relationships
between types of fat consumption and heart disease in people with
diabetes. "Previous studies have demonstrated that monounsaturated fat has particular benefits on blood
lipids and glucose response among diabetics," said Hu. "But the effects
of monounsaturated fat on risk of heart disease among diabetics
have not been studied."
Frank Hu's recent research on the
relationship between egg consumption and heart disease is
the subject of an American Medical Association
video presentation.
Having an egg a day unlikely to increase risk of heart disease in healthy
men and women -- AMA Press Release of April 21, 1999.
AMA video coverage 
28.8 Kbps |
56 Kbps |
112 Kbps
