Here’s a recent nutrition research headline: “High carb intake linked to early Alzheimer’s.” If you’re like most busy people today, you read the headline and conclude that high carb intake causes Alzheimer’s disease. Fair conclusion? Not at all.
The study depended entirely on people truthfully and accurately reporting what they eat. The subjects were 70-89 years old. The investigators started with 1230 people and weeded that group down to 940 people who didn’t exhibit signs of dementia. Those people were asked to report what they’d eaten in the past year. Can you remember what you ate for the past year?
The subjects were followed for 4 years for signs of cognitive decline. Less than 1/4 of the subjects were classified as having Mild Cognitive Decline (MCD). People with higher carbohydrate intake, especially from sugar, were more likely to be in that group. People with higher fat intake were less likely. Did the carbs cause cognitive decline? It’s completely impossible to make that conclusion.
- Elderly people may develop cognitive problems anyway, regardless of diet. And not all cognitive decline progresses to Alzheimer’s disease, so jumping to the conclusion that carbs raise the risk for Alzheimer’s disease is irresponsible.
- As one prominent research points out, Alzheimer’s disease begins 10-15 years before symptoms appear. Suggesting that diet from a previous year caused it is unlikely.
- Perhaps people who are experiencing early stages of Alzheimer’s disease start to choose higher carb and sweeter foods for some reason. Meaning disease causes diet. I’m not aware of any studies on that possibility.
- Asking people to voluntarily report what they ate for the past year is asking for trouble, regardless of age. People forget, they try to give the researchers a “good” story, and so forth. Here’s another wrinkle: those people who were already in the early states of cognitive impairment were already less able to correctly remember their diet.
There’s plenty of diet survey research linking healthier eating to lower risk for cognitive decline, dementia and Alzheimer’s disease. Prevention is a good strategy, and generally healthy diets, high in plant foods, are the most promising when it comes to preserving brain function. Contrary to what you might conclude that the headline, a low carb diet is not likely to ward off cognitive decline.
The National Institute on Aging has more Alzheimer’s facts here.