I read about a study linking a high-fat diet to memory loss. How much fat is too much?
You are probably talking about a University of Oxford study published in the online version of the FASEB Journal (the journal of the Federation of American Societies for Experimental Biology) on Aug. 10. For that study, researchers examined the effects of a very high-fat diet and a very low-fat diet on 32 rats on their ability to remember their way through a maze and on their performance on a treadmill.
The researchers found that after just a few days on the high-fat diet -- consisting of a whopping 55 percent of calories from fat -- the rats had more trouble recalling how to get through the maze, and they also performed 30 percent worse on the treadmill after just a few days on the high-fat diet, compared to when they were on a diet consisting of only 7.5 percent of calories from fat.
The researchers said they also have performed similar studies on humans, but those results haven't been published yet. Assuming the human studies show comparable results, what does that mean for your diet?
Well, probably not much, at least if you tend to stick close to official recommendations for fat intake. The U.S. Dietary Guidelines have long suggested that total fat intake for adults be anywhere from 20 percent to 35 percent of total calories. That's nowhere near the low-fat diet of 7.5 percent of total calories or the high-fat diet of 55 percent of total calories used in the rat study.
Now, if you tend to binge on high-fat foods over the course of a few days, you might find your poor diet has an effect -- either on your cognitive ability, your physical ability, or both. But certainly that wouldn't be the only reason to switch back to healthier eating habits: High-fat diets are associated with higher risks of heart disease and some types of cancer, especially diets high in saturated or trans fats.
In fact, official guidelines recommend keeping saturated fat to 10 percent of calories consumed, and eliminating, if at all possible, trans fat intake. That means, for example, if your recommended calorie intake for the day is 1,600 calories a day (the amount recommended for sedentary women age 51 or older), you should limit saturated fat to 18 grams or less. If you consume 2,400 calories a day (recommended for active women ages 14-30 or most sedentary men ages 16-40), limit saturated fat to 26 to 27 grams.
The other 10 to 25 percent of calories from fat should come from monounsaturated and polyunsaturated fats. Check Nutrition Facts labels for good sources.
Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or filipic.3@cfaes.osu.edu.
Editor: This column was reviewed by Julie Shertzer, registered dietitian and program specialist for Ohio State University Extension in the Department of Human Nutrition, in the College of Education and Human Ecology.