A large bowl of oat bran cereal each day modestly lowers cholesterol in people with high cholesterol levels but may make little difference for others, the largest study of its kind shows.
A review of 10 trials that tested oat bran's cholesterol-lowering potential found that eating about 1 ounce of oat bran daily cut total cholesterol levels about 6 percent to 7 percent in people with high cholesterol levels. More than 229 milligrams of cholesterol per deciliter of blood was considered a high cholesterol count.However, the reviewers concluded Tuesday that people whose blood cholesterol levels are already low "may demonstrate little change in total cholesterol level by introducing a single serving of oats into their diet."
"For people who want to know, `How will oats affect me?' our answer is, `It depends.' It depends on your initial cholesterol level and how much oats you are going to be eating," said Cynthia Ripsin of the University of Minnesota in Minneapolis, head of the review published in the Journal of the American Medical Association.
Ripsin emphasized that her study, which received about one-quarter of its $50,000 in funding from Quaker Oats Co. of Barrington, Ill., did not look at whether oat bran was more effective in lowering cholesterol than other sources of soluble fiber, such as beans or rice bran.
The controversy over whether oat bran helps cut cholesterol has been going on since 1963, when a three-week study of 21 men found that substituting oatmeal bread for regular wheat bread cut their cholesterol levels by about 11 percent.
Some researchers, such as Dr. Frank Sacks at Brigham and Women's Hospital in Boston, have argued that oat bran does not possess any special cholesterol-lowering ability. Instead, Sacks says filling up on foods rich in oat fiber simply reduces people's intake of higher-fat foods.
Others, including Dr. James Anderson at the University of Kentucky in Lexington, theorize that the water-soluble fiber in oat bran lowers cholesterol by increasing the loss of cholesterol-carrying products, called bile acids, from the body.
The latest review was conducted in an effort to settle that debate.
Sacks said the new research was well done, but he added: "The cholesterol-lowering effect found by pooling all the studies is so small as to be trivial.
"Rather than being obsessed with oat bran, people should be thinking about overall dietary changes like lowering their intake of saturated fat and cholesterol," Sacks said.
The researchers pooled data from 10 published and unpublished trials of oat products involving 1,278 people.