Questions over fat, heart disease link

Many of us have long been told that saturated fat, the type found in meat, butter and cheese, causes heart disease. But an exhaustive new analysis by a team of international scientists found no evidence that eating saturated fat increased heart attacks and other cardiac events.

The new findings are part of a growing body of research that has challenged the accepted wisdom that saturated fat is inherently bad for you and will continue the debate about what foods are best to eat. For decades, health officials have urged the public to avoid saturated fat as much as possible, saying it should be replaced with the unsaturated fats in foods like nuts, fish, seeds and vegetable oils.

But the new research, published on Monday in the journal Annals of Internal Medicine, did not find that people who ate higher levels of saturated fat had more heart disease than those who ate less. Nor did it find less disease in those eating higher amounts of unsaturated fat, including monounsaturated fat like olive oil or polyunsaturated fat like corn oil. “My take on this would be that it’s not saturated fat that we should worry about” in our diets, said Dr Rajiv Chowdhury, the lead author of the new study and a cardiovascular epidemiologist in the department of public health and primary care at Cambridge University.

But Dr Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health, said the findings should not be taken as “a green light” to eat more steak, butter and other foods rich in saturated fat. He said looking at individual fats and other nutrient groups in isolation could be misleading, because when people cut down on fats they tend to eat more bread, cold cereal and other refined carbohydrates that can also be bad for cardiovascular health.

Mediterranean diet“The single macronutrient approach is outdated,” said Dr Hu, who was not involved in the study. “I think future dietary guidelines will put more and more emphasis on real food rather than giving an absolute upper limit or cutoff point for certain macronutrients.”

He said people should try to eat foods that are typical of the Mediterranean diet, like nuts, fish, avocado, high-fiber grains and olive oil. A large clinical trial last year, which was not included in the current analysis, found that a Mediterranean diet with more nuts and extra virgin olive oil reduced heart attacks and strokes when compared with a lower fat diet with more starches.

Alice H Lichtenstein, a nutritional biochemist at Tufts University, agreed that “it would be unfortunate if these results were interpreted to suggest that people can go back to eating butter and cheese with abandon,” citing evidence that replacing saturated fat with foods that are high in polyunsaturated fats – instead of simply eating more carbohydrates – reduces cardiovascular risk. Dr Lichtenstein, who was not involved in the latest study, was the lead author of the American Heart Association’s dietary guidelines, which recommend that people restrict saturated fat to as little as 5 percent of their daily calories for the typical person eating about 2,000 calories a day.

The heart association states that restricting saturated fat and eating more unsaturated fat, beans and vegetables can protect against heart disease by lowering low-density lipoprotein or so-called bad cholesterol.

In the new research, Dr Chowdhury and his colleagues sought to evaluate the best evidence to date, drawing on nearly 80 studies involving more than a half million people. They looked not only at what people reportedly ate, but at more objective measures such as the composition of fatty acids in their bloodstreams and in their fat tissue.

The scientists also reviewed evidence from 27 randomised controlled trials – the gold standard in scientific research – that assessed whether taking polyunsaturated fat supplements like fish oil promoted heart health.

The smallest and densest form of LDL is more dangerous. These particles are easily oxidised and are more likely to set off inflammation and contribute to the buildup of artery-narrowing plaque. An LDL profile that consists mostly of these particles, known as pattern B, usually coincides with high triglycerides and low levels of HDL, both risk factors for heart attacks and stroke.

So it is possible that the benefits of omega-3 fatty acids lie in preventing heart disease, rather than treating or reversing it. At least two large clinical trials designed to see if this is the case are currently underway.