Striking a balance between two healthy forms of dietary fat may be key to lowering blood cholesterol, according to new research.

Researchers found that a diet rich in a new type of sunflower oil - which had relatively high concentrations of both polyunsaturated fatty acids and monounsaturated fats - bested olive oil when it came to lowering levels of “bad” LDL cholesterol among 31 men and women.

The findings, say the researchers, point to the importance of replacing saturated fats in the diet with a “balance” of monounsaturated and polyunsaturated fats. While olive oil is rich in monounsaturated fat, it has far lower levels of polyunsaturated fatty acids, or PUFAs.

Striking a balance between two healthy forms of dietary fat may be key to lowering blood cholesterol, according to new research.

Researchers found that a diet rich in a new type of sunflower oil - which had relatively high concentrations of both polyunsaturated fatty acids and monounsaturated fats - bested olive oil when it came to lowering levels of “bad” LDL cholesterol among 31 men and women.

The findings, say the researchers, point to the importance of replacing saturated fats in the diet with a “balance” of monounsaturated and polyunsaturated fats. While olive oil is rich in monounsaturated fat, it has far lower levels of polyunsaturated fatty acids, or PUFAs.
The sunflower oil’s supply of both types of fat appear to be the reason for its LDL-fighting ways, the study authors report in the Journal of the American Dietetic Association.

Saturated fat is found mainly in animal products, including meat and higher-fat dairy products. Unsaturated fatty acids, which are either monounsaturated or polyunsaturated, are found in foods like vegetable oils, nuts, seeds and fatty fish.

But vegetable oils differ in their concentrations of the two types of unsaturated fat. Olive oil is rich in monounsaturated fat, but has lower PUFA levels and more saturated fat than many other vegetable oils, including canola, safflower and sunflower oils.

The sunflower oil used in the current study - sold as NuSun by the National Sunflower Association - is a new brand designed to make commercial foods that are free of so-called trans fats. These fats are created when vegetable oils undergo a chemical process called hydrogenation, which makes the oils more solid and able to hold up to commercial cooking and baking processes.

The problem with trans fats, which are found in a range of commercial baked goods, snack foods, shortening and stick margarines, is that, like saturated fat, they can raise LDL cholesterol levels.

But it’s not NuSun’s lack of trans fats that appeared key in the current study, which received partial funding from the product’s Bismark, North Dakota-based manufacturer.

Instead, the oil’s balance of poly- and monounsaturated fats may bestow the cholesterol benefit, according to the study authors, led by Dr. Penny Kris-Etherton of Pennsylvania State University in University Park.

She and her colleagues had the 31 study participants follow each of three 4-week diets: one heavy in foods containing the sunflower oil, another rich in olive oil and one typical of the “American” diet. Both of the oil-based diets contained the same amount of saturated fat, but the sunflower-oil diet had a greater balance between mono- and polyunsaturated fats. The American diet had more saturated fat and more total fat than either of the other two diets.

After following the sunflower-oil diet, study participants showed a 6 percent drop in their LDL levels compared with their time on the American diet. In contrast, the diet rich in olive oil showed no significant effect on LDL levels.

“Within the context of a moderate-fat diet,” the study authors write, “it is becoming clear that a mixture of unsaturated fatty acids provides the greatest health benefits.”

“Therefore,” they add, “an emphasis on a balance of unsaturated fatty acids is important when selecting food sources to replace saturated fatty acids in the diet.”

SOURCE: Journal of the American Dietetic Association, July 2005.