What Are the Best Fats to Use in The Diet for Heart Health?
| For many years, nutritionists have recommended reducing saturated fats in the diet to lower the risk of heart disease. However, what has not been well known is what food should be used in place of the saturated fat – monounsaturated fatty acids (MUFA) such as found in olive oil and canola oil, polyunsaturated fatty acids (PUFA) as found in soy oils and many other vegetable oils, or keeping all fat intake low and replacing saturated fat with carbohydrates?
A new study by Harvard University addresses this issue by doing a meta-analysis (combining data from 8 randomized control trials) where they monitored what people ate for 4+ years while they reduced saturated fat in the diet and compared replacing it with polyunsaturated fat to see how this affected death rates from coronary heart disease (CHD).
The study included 13,614 people and over the 4.5 years they had 1,042 CHD events (such as a heart attack or death from heart disease). Researchers found that people who replaced saturated fats with PUFAs had the best decrease in CHD events. For every 5 percent increase in PUFA in the diet, CHD dropped by 10 percent. The average intake of PUFA was 15 percent of calories eaten in the experimental group, compared to only 5 percent of calories from PUFA in the control group. Compared to controls, those who ate the high-PUFA diet (15 percent of calories) had a 19 percent decrease in deaths from CHD. This is one of the first randomized control trials where researchers actually changed people's diets and measured the effect actual CHD rates.
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When comparing primary prevention (only people without any history of heart disease), the drop in risk was even greater, a 25 percent decrease in deaths from CHD on the high PUFA diet. The duration of the study also had an effect. For every study that continued on longer than 4.25 years, researchers saw an additional 9 percent reduction in deaths from CHD. In other words, the longer they stayed on the higher PUFA diet, the lower their risk of CHD. The 4 studies lasting longer than 4.25 years showed a 27 percent decrease in deaths from CHD.
The researchers further pointed that in an analysis of 11 prospective studies where carbohydrate was used to replace saturated fat in the diet they found no decrease in CHD. When you reduce saturated fat and replace it with carbohydrate (grains, vegetables, legumes) blood LDL cholesterol levels fall, but so do the protective HDL cholesterol levels, thus no significant decrease in CHD occurs. When saturated fat is replaced with PUFA, LDL cholesterol levels fall and HDL cholesterol levels remain high thus explaining why CHD decreased. The authors reported that when monounsaturated fats are used to replace saturated fat, the results were mixed. Some studies showed a drop in CHD, others didn't. PUFA however, showed a clear, consistent decrease in CHD.
The authors concluded their study by saying, "These findings provide evidence that consuming polyunsaturated fats in place of saturated fats reduces coronary heart disease." They also stated that the lower risk of CHD from dietary changes "may be more strongly related to increased PUFA than decreased saturated fat consumption." Polyunsaturated fats, in addition to lowering LDL cholesterol, also have other non-lipid benefits such as decreasing insulin resistance (thus lowering blood glucose levels), and reducing systemic inflammation. Both of these benefits would help lower heart disease as well as diabetes risk.
The authors also made a point to put all of this in perspective. The reduction in saturated fat and increase of PUFA can reduce CHD risk moderately (19-27 percent). However, there are other dietary changes that could contribute to even greater reductions in CHD such as:- Cutting the intake of salt in the diet (The Institute of Medicine recommends less than 1,500 mg of sodium/day for adults age 50 and older and those with high blood pressure.)
- Eating more whole grains (Data from the Nurses' Health Study showed that among women who don't smoke, those who ate at least 3 servings of whole grains daily had a 50 percent decrease in CHD compared to women who seldom ate whole grains.)
- Eating more fruits and vegetables (Data from the INTERHEART study of 52 nations showed that those who ate the most fruit and vegetables daily had a 30 percent reduction in CHD compared to those eating few fruits and vegetables.)
- Eating foods high in omega-3 fatty acids (such as fish, walnuts, flax meal, etc.)
Source:
Mozaffarian D, et al. Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat. PLOS Medicine. 2010;7(3):1-10.
Examples of PUFA and MUFA fats:- Examples of foods high in MUFA are: olive oil, Canola oil, cashews, olives, avocado.
- Examples of foods high in PUFA are: soy oil and soy foods, corn oil, walnuts, flax meal, fish.
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