For the last few years, Cheerios boxes and ads have promoted the cereal's ability to help lower cholesterol; last year, for a time, ads promised the cereal could lower cholesterol by a very specific 4% in six weeks. (Cereal maker General Mills removed that particular claim from boxes after receiving a warning letter from the Food and Drug Administration in May stating that the claim had not been approved by the agency.) A few other products, including Quaker Oatmeal Squares and Kashi Heart to Heart, claim to be able to help lower cholesterol too.
Those claims are based on the fact that the cereals are made from whole grain oats and oat bran, sources of a type of soluble fiber called oat beta-glucan, which has been linked to reduced levels of LDL, or bad, cholesterol.
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But this doesn't mean your breakfast cereal can replace your Lipitor — or take the place of the broader dietary changes necessary to lower cholesterol.
The soluble fiber in some breakfast cereals can help lower cholesterol levels, but it would likely take more than a single bowl in the morning to get the desired effect, says Dr. Leslie Cho, director of the Cleveland Clinic's Women's Cardiovascular Center in Cleveland.
It takes at least 3 grams of soluble fiber per day to reduce cholesterol, Cho says. To get that amount from a breakfast cereal, one would generally have to consume 3 cups — that's three servings — a day.
"That's a lot of soluble fiber, but it comes at a cost of lots of sugar," says Cho. Regular Cheerios provides 1 gram of soluble fiber and 1 gram of sugar per serving; Honey Nut Cheerios provides less than 1 gram of soluble fiber and 9 grams of sugar. (Sugar takes its own toll on heart health by contributing to weight gain and increasing the risk of diabetes, Cho says.)
Further, other foods are richer sources of soluble fiber. A half-cup of oatmeal provides 2 grams of the fiber, an orange provides 1.7 grams, and a serving of black beans provides 2.4 grams.
Fiber is generally divided into two types. Insoluble fiber, found in whole wheat, nuts and vegetables, resists digestion and helps prevent constipation. Soluble fiber, found in oats, beans and legumes, is dissolvable in water and in recent decades has been linked to lower cholesterol levels and a reduced risk of heart disease.
A review of the evidence on soluble fiber, published in the Journal of Family Practice in 2006, concluded that eating 5 grams to 10 grams of soluble fiber per day was associated with a 10% to 15% reduction in LDL levels — which, the researchers estimated, could lower heart disease risk by 10% to 15%.
Other studies have assessed the effects of the specific types of soluble fiber, including oat beta-glucans, psyllium (a seed husk found in many over-the-counter laxatives), pectin (a carbohydrate found in many fruits and vegetables) and guar gum (derived from the beans of the guar plant).
In 1999, Harvard University researchers published in the American Journal of Clinical Nutrition a review of the evidence from 67 studies on the link between intake of different types of soluble fiber and blood cholesterol levels. The studies on oat products showed that getting an average of 5 grams of soluble fiber from oats for an average of 39 days reduced LDL levels by about 3.6%.
Oats were not the most powerful cholesterol-reducers in the studies reviewed; psyllium lowered cholesterol levels about 6% among people who consumed an average of 9 grams for an average of 53 days, and an average of 4.7 grams of pectin consumed for an average of 34 days reduced cholesterol levels roughly 6.5%.
A more recent review, published in the journal Nutrition Reviews last year, looked at both the overall effects of fiber intake and the effects of specific types of soluble fiber on cholesterol levels and heart health. Pooling results from seven large studies that followed a total of 158,000 adults, the researchers found that heart disease prevalence was 29% lower in the group with the highest total dietary fiber intake compared to the lowest. But, of course, this could have been due to the overall healthier lifestyles among those who tend to eat high-fiber diets.
Researchers also found that consuming an average of about 6 grams of soluble fiber per day for about four to eight weeks reduced LDL by just over 5%; the reduction was similar when they looked specifically at studies on oat beta-glucan. The review was partially funded by the National Fiber Council.
A few studies, some published, some not, have looked specifically at the cholesterol-lowering effects of oat cereals, showing a 1% to 5% reduction in cholesterol over several weeks, says Dr. David Heber, professor of medicine and director of the Center for Human Nutrition at UCLA. "These are small reductions," Heber says. Reductions of 1% in particular, he said, are "not really significant from a medical standpoint."
Adult men need 30 to 38 grams of total fiber per day, while women need 21 to 25 grams, according to the Institute of Medicine. All adults need about 5 of those grams to be soluble fiber, says Heber. The American Heart Assn. puts oatmeal, beans, peas, citrus fruits and strawberries on its list of foods high in soluble fiber.
Although soluble fiber can help lower cholesterol, it should not be the only dietary change people with high cholesterol make, says Sara Wolf, clinical manager of outpatient dietetics at the Mayo Clinic in Rochester, Minn.
In addition to eating more fiber-rich whole grains, fruits and vegetables, Mayo patients are counseled to make a number of nutritional improvements, such as consuming foods high in polyunsaturated fats and omega-3 fatty acids, she says.
Cho adds that no single food or food component can reduce cholesterol in the absence of overall dietary change. "If you want to lower your cholesterol, you have to limit dairy, red meat and eggs," says Cho.
Cho also recommends eating all foods in moderation, reading food packaging labels and using common sense. For instance, she says, "if you're eating Cheerios to lower your cholesterol, it makes no sense to eat them with whole fat milk."