Dietary Cholesterol Makes LDL Cholesterol More Radical

A little extra cholesterol in our diets may render the “bad” LDL cholesterol in our bloodstream more susceptible to oxidation. That’s what happened to the LDL from a group of older men and women in a study reported in the March issue of Atherosclerosis.

And that’s not good: Evidence suggests that oxidized LDL cholesterol is more apt to provoke the plaques that build up in arteries and increase risk of heart attack and stroke.

The researchers concluded that the current recommendation to limit dietary cholesterol is both valid and prudent, noting that their findings support those of an earlier study by others. This study was led by Ursula S. Schwab and Alice H. Lichtenstein at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston.

Schwab, who is now back in Finland, Lichtenstein and colleagues designed 30-percent-fat diets that differed only in the type of fat. One was rich in polyunsaturated fat from corn oil; the other was rich in saturated fat from beef tallow. Otherwise, the foods were identical.

And by adding extra cholesterol to each diet--ranging from around 220 to 330 milligrams, depending on the volunteer’s total calorie intake--they approximately doubled the cholesterol content. That’s considerably more than the 300-milligrams recommended by the Dietary Guidelines.

Thirteen men and women between the ages of 46 and 78 ate each of four diets, the corn oil with and without the extra cholesterol and beef tallow with and without extra cholesterol.

The type of fat didn’t significantly affect the susceptibility of the volunteers’ LDL to oxidation in a test-tube assay. But the extra cholesterol increased oxidation susceptibility by 28 percent during the corn oil diet and 15 percent during the beef tallow diet.

The volunteers began the study with moderately elevated LDL cholesterol--each having levels greater than 130 milligrams per deciliter. Adding the extra dietary cholesterol prompted a further rise in their total as well as their LDL cholesterol, regardless of the type of fat in the diet.

Scientific contact: Alice H. Lichtenstein, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Mass., phone (617) 556-3127, fax (617) 556-3103, [email protected].