Modified fat diet key to lowering heart disease risk

A low fat diet replaces saturated fat — such as or animal or dairy fat — with starchy foods, fruits and vegetables, while a modified fat diet replaces saturated fat with monounsaturated and polyunsaturated fats, found in foods such as liquid vegetable oils, fish, nuts and seeds.

Lead review author Lee Hooper, M.D., said she and her colleagues were surprised there was such a clear difference between the effects of the diets.

Hooper, a senior lecturer in research synthesis and nutrition at Norwich Medical School at the University of East Anglia, in England, said the main theory has been that eating saturated fat raises LDL cholesterol, which raises our risk of cardiovascular disease and therefore should make the effects of a low fat diet and a modified fat diet very similar.

“However, the review shows clearly that modified fat diets appear to be more effective in reducing the risk of cardiovascular events than low fat diets,” she said. “This could be due to a low fat diet being harder to maintain, but this is not clear.”

The review appears in the July issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

The authors published an earlier version of this review in 2000, in which 27 randomized controlled studies were included. This current version analyzes 48 studies conducted between 1965 and 2009 and including 65,508 participants from around the globe. Participants were all adults who had heart disease, were at risk of heart disease or were from the general healthy population. All studies reduced or modified participants’ dietary fat or cholesterol for at least six months by at least 30 percent.

Hooper and her team found that reducing saturated fat in diets reduced the risk of having a cardiovascular event, such as heart attack, stroke and unplanned heart surgery, by 14 percent. Of the 65,508 participants, 7 percent had a cardiovascular event. Researchers noted benefits in individuals who followed a modified diet for at least two years.

Yet, is a 14 percent reduced risk enough to motivate people to change their diets?

“In my experience people are very individual as far as what motivates them to make dietary changes,” said Rachel Johnson, a professor of medicine at the University of Vermont. “Many counselors assess their clients’ stages of change to determine whether they are open to making lifestyle changes.”

Johnson said that among others, the stages of change include (1) pre-contemplation: not yet acknowledging there is a problem behavior that needs to be changed, (2) action/willpower: changing behavior and (3) maintenance: sustaining the behavior change.

“Information like this study provides may be helpful in motivating people who have moved past the pre-contemplation stage to make a change,” she added.

The Cochrane reviewers were unable to find proof that making long-term reductions to dietary fat intake had any effect on a person’s risk of death by cardiovascular causes, including heart attack, stroke and diabetes. The evidence also was not clear as to whether currently healthy people would benefit by reducing fat in their diets as much as those who are already at risk of heart disease.

“There is no clear difference in effect in people at increased risk of cardiovascular disease and in the general population,” said Hooper. She added, though, that data suggest “we would all benefit to some extent.”

The American Heart Association (AHA) recommends watching both your intake of trans fat and saturated fat. The association suggests people eat less than 7 percent of total calories from saturated fat and less than 1 percent of total calories from trans fat.

And while, according to the AHA website, Americans should reduce “bad” fats in our diet and replace them with the “better” fats — monounsaturated and polyunsaturated fats — the Cochrane reviewers found it was not clear which of these fats are more beneficial.

More information: Hooper L, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database of Systematic Reviews 2011, Issue 7.

Provided by Health Behavior News Service