We already know that diets rich in fat, particularly artery-clogging trans fat, are bad for the heart and the waistline.
The new study is the largest to look at stroke risk in women and across all types of fat. It showed a clear trend: Those who ate the most fat had a 44 percent higher risk of the most common type of stroke compared to those who ate the least.
"It's a tremendous increase that is potentially avoidable," said Dr. Emil Matarese, stroke chief at St. Mary Medical Center in Langhorne, Penn. "What's bad for the heart is bad for the brain."
He reviewed but did not help conduct the research, which was presented Wednesday at an American Stroke Association conference. It involved 87,230 participants in the Women's Health Initiative, a federally funded study best known for revealing health risks from taking hormone pills for menopause symptoms.
Before menopause, women traditionally have had less risk of stroke than similarly aged men, although this is changing as women increasingly battle obesity and other health problems.
After menopause, the risk rises and the gender advantage disappears, said Dr. Ka He, a nutrition specialist and senior author of the study from the University of North Carolina, Chapel Hill.
He and another researcher, Sirin Yaemsiri, wanted to see whether dietary fat affected the odds.
Participants in the study had filled out detailed surveys on their diets when they enrolled, at ages 50 to 79. Researchers put them into four groups based on how much fat they ate, and looked about seven years later to see how many had suffered a stroke caused by clogged blood vessels supplying the brain - the most common kind.
There were 288 strokes in the group of women who consumed the most fat each day (95 grams) versus 249 strokes in the group eating the least fat (25 grams), Yaemsiri told the conference.
After taking into account other factors that affect stroke risk - weight, race, smoking, exercise and use of alcohol, aspirin or hormone pills - researchers concluded that women who ate the most fat had a 44 percent greater risk of stroke.
They also found a 30 percent greater risk of stroke among women eating the most trans fat, which is common in stick margarine, fried foods, crackers and cookies.
"We need to look at the labels on the foods we buy," because many of these fats are hidden in baked goods and people are not aware of how much they're consuming, Matarese said. "This is a simple way that any woman, especially postmenopausal women, can improve their health. Simply avoiding fried foods is a big one."
On average, American women in their 50s and 60s eat 63 to 68 grams of fat a day, federal health statistics show. A little context: A 2-ounce Snickers bar contains 14 grams of fat; a 2-ounce bag of Crunchy Cheetos has 20 grams, as does a Haagen-Dazs ice cream bar.
The American Heart Association recommends limiting fat to less than 25 to 35 percent of total calories, and trans fat to less than 1 percent. The healthiest fats come from nuts, seeds, fish and vegetable oils.
"We don't do a good enough job of emphasizing the importance of a good diet," said Dr. Lee Schwamm, a stroke specialist at Massachusetts General Hospital. Pediatricians in particular need to address the risk for chubby kids.
"If you don't change their patterns and problems in childhood, you're really looking at a lifetime of obesity," he said.
On the Web
American Stroke Association: http://www.strokeassociation.org/