June 7, 2002 -- Olive oil. Canola oil. Corn oil. Here's more thumbs-up evidence that eating vegetables -- and stuff made from veggies, like oils -- is best for your health. In fact, old-fashioned corn oil margarine may be nearly as effective as the expensive cholesterol-lowering spreads.
All vegetables and veggie-based products contain chemicals called phytosterols, which block the intestine from absorbing cholesterol -- thereby reducing LDL cholesterol in your blood, cutting heart disease risk. Large amounts of phytosterols have a dramatic effect on cholesterol, as many studies have shown.
That's why cholesterol-lowering spreads work, because they're loaded with phytosterols, says Richard E. Ostlund Jr., MD, an epidemiologist with Washington University School of Medicine in St. Louis.
But little is known about the smaller amounts phytosterols present naturally in food products like corn oil -- one of the richest sources of phytosterols. Could the little bit used in cooking actually affect cholesterol levels? Could a dab of corn oil margarine reduce your "bad" LDL cholesterol?
"We have assumed that small amounts were unimportant," he tells WebMD. Turns out, a little vegetable oil is very important.
His study -- published in the recent American Journal for Clinical Nutrition -- shows solid evidence. He fed 25 people two meals: a pudding that contained 35 milligrams of cholesterol and 30 to 35 grams of corn oil. Some got corn oil from which the phytosterols had been removed; others got regular corn oil.
Those who ate corn oil without phytosterols had a 38% jump in cholesterol absorption -- which means more cholesterol got into their veins.
Those who ate a meal with phytosterols had 12% less cholesterol in their blood. "This indicates that phytosterols are reducing cholesterol absorption," he tells WebMD. "It will almost certainly result in significant lowering of cholesterol as well."
"We're not saying drink corn oil, not yet," says Ostlund. "We're saying that phytosterols are an important plant nutrient, and that even small amounts affect cholesterol absorption."
In fact, "corn oil margarines -- and other vegetable-derived margarines -- contain phytosterols in varying amounts and may well affect LDL levels," he tells WebMD.
It's more evidence that a plant-based diet is the way to go, says Cynthia Sass, RD, a senior dietitian in the health education department of the University of South Florida. She is also a spokeswoman for the American Dietetic Association.
"People are recognizing that not all fats are bad," she tells WebMD. "They realize they should reduce animal fats, but that healthy plant fats are fine. Nuts, seeds, vegetable oils are fine in moderate amounts."
It's good to mix it up -- use different types of oils -- because you're exposing your body to a bunch of different, very healthy chemicals, she says.
"Moderation, variety, balance" -- that's the mantra of the ADA, Sass tells WebMD. "It's the best way to ensure you don't get too much or too little of something. That way, you don't get caught up in the nutrient of the day."
One caveat: The more refined the oil, the worse it is for you, says Ostlund. "Refining removes phytosterols. In fact, the refining process for palm oil removes nearly all phytosterols. That may contribute to some of the adverse effects of palm oil. The other effects might be due to saturated fat that remains in the oil."