Higher Blood Saturated Fat Increases Dementia Risk

In a study of more than 1,200 people, researchers show that individuals with higher levels of saturated fats in their blood are more likely to develop dementia, including Alzheimer’s disease. Researchers published their findings in the American Journal of Clinical Nutrition. 

This project was supported by an Alzheimer’s Disease Research (ADR) grant to senior author Majken Jensen, PhD, who is affiliated with both the Harvard T.H. Chan School of Public Health and the University of Copenhagen in Denmark. First author Manja Koch, PhD, also at Harvard, was a participant in the BrightFocus 2018 Alzheimer’s Fast Track Workshop.

When scientists study how diet influences the development of diseases, such as Alzheimer’s disease (AD), they often rely on someone’s own report of what they have eaten, which is not always accurate. A more reliable approach is to monitor blood samples of people participating in scientific studies. This tracking allows researchers to figure out what sort of foods the subjects are eating and then determine whether people who consume a lot of a certain type of nutrient are more likely to get sick.

In a newly published study that was funded in part by BrightFocus, a team led by Dr. Jensen and Dr. Koch looked for 45 different types of fat particles that could be circulating in the blood of 1,252 elderly individuals, 498 of whom developed dementia within about five years of their blood draw. Participants were part of the Gingko Evaluation of Memory Study (GEMS), a clinical trial originally designed to examine the preventive effect of ginkgo biloba on dementia in older adults. Using collected blood samples from the trial, these researchers found that people with higher levels of saturated fats in their blood were more likely to experience cognitive losses and develop Alzheimer’s disease than individuals with higher levels of linoleic acid, a polyunsaturated omega-6 fatty acid which is found in many plant oils.

Scientists had already begun to link higher dietary saturated fat intake to higher risk of dementia and cognitive decline, but this study is one of the first to use blood tests in such a large number of people in order to understand the link between diet and later brain health. In the future, researchers will likely look into the effects of specific fat-related diet interventions on the risk of dementia and Alzheimer’s.

It is still early to make any recommendation based on these findings, but past research has shown it is prudent to choose vegetable oils like olive, canola, soy, corn, sunflower, peanut, and others, and avoid partially hydrogenated oils, which contain trans fats. Dr. Jensen, Dr. Koch, and colleagues did not find a direct link between trans fats and dementia or cognitive decline in the new study, but artificial trans fats have been banned in the United States due to their link to type 2 diabetes and cardiovascular disease, both of which are themselves risk factors for dementia. This new work helps confirm that saturated fats—found in many foods, including butter, cheese, red meat, and coconut oil—are best consumed in moderation when it comes to dementia risk and also overall health.