Analysis fails to link saturated fat with heart disease

February 9, 2010 in Heart Health, Nutrition Topics in the News

Analysis fails to link saturated fat with heart disease
The saturated fat found mainly in meat and dairy products has a bad reputation, but a new analysis of published studies finds no clear link between people's intake of saturated fat and their risk of developing heart disease.

Research has shown that saturated fat can raise blood levels of "bad" LDL cholesterol, and elevated LDL is a risk factor for heart disease and stroke. Because of this, experts generally advise people to limit their intake of fatty meat, butter and full-fat dairy products.

But in the new analysis, which combined the results of 21 previous studies, researchers found no clear evidence that higher saturated fat intakes led to higher risks of heart disease or stroke.

The findings, published in the American Journal of Clinical Nutrition, may sound like good news for steak lovers, but experts caution against "over interpreting" the results.

Many studies have shown that dietary saturated fat can raise people's cholesterol, and the new analysis is not going to change recommendations to keep saturated fat intake in check.

Perhaps more importantly, though, is that the thinking on diet and heart health is moving away from a focus on single nutrients and towards "dietary patterns."

A number of studies have linked the so-called Western diet to greater heart disease risks; that diet pattern is defined as one high in red and processed meats and saturated fats -- but also high in sweets and other refined carbohydrates like white bread.

On the other hand, diets described as Mediterranean or "prudent" -- generally high in fruits and vegetables, whole grains, fish, unsaturated fats from vegetable oil -- may help lower the risk of heart disease and stroke.

For the current study, researchers from the Children's Hospital Oakland Research Center in California, pooled data from 21 studies that included a total of nearly 348,000 adults.

Participants, who were generally healthy to start, were surveyed about their diet habits and then followed for anywhere from five to 23 years. Over that time, 11,000 developed heart disease or suffered a stroke.

Overall, there was no difference in the risks of heart disease and stroke between people with the lowest and highest intakes of saturated fat.

The analysis included what are known as epidemiological studies -- where the researchers looked for associations between people's reported diet habits and their risk of heart disease and stroke. These types of studies have inherent limitations, like depending on people's recollection of their eating habits.

The study could not address whether the effects of replacing saturated fat in the diet with polyunsaturated fats -- like those found in vegetable oils and fish -- or with carbohydrates.

Some other studies, the researchers write, have shown that consuming polyunsaturated fats in place of saturated ones may lower heart disease risk.

Studies that have shown a beneficial effect on heart disease risk by lowering saturated fat have replaced saturated fat with polyunsaturated fat.  The main sources of polyunsaturated fat include cooking oils (e.g. sunflower, safflower, soybean, corn, grapeseed, hemp, flaxseed, and walnut oil) and oily fish.

In other words, cutting back on saturated fat may not lower the risk for heart disease unless you also increase your polyunsaturated fat intake.  

When it comes to carbohydrate, replacing saturated fat with carbohydrates - mainly refined - may actually increase the risk of heart disease in certain people. Replacing saturated fat with carbohydrate - especially refined - in conjunction with obesity can create a metabolic environment that favours heart disease by boosting blood triglycerides (fat), lowering HDL cholesterol and increasing small, dense LDL particles - the type of LDL considered more harmful to heart health.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.