In a study published online in JAMA Neurology, researchers found that dietary saturated fat reduced the body’s levels of apolipoprotein E, also called ApoE, which helps remove amyloid beta proteins out of the brain. Essentially, people who received a high-saturated-fat, high-sugar diet showed a change in their ApoE, such that the ApoE would be less able to help clear the amyloid.
ApoE4 status is associated with an increased risk of cognitive decline and elevated brain amyloid deposition. It is believed that the different forms of ApoE (2, 3 and 4) appear to regulate the removal of beta-amyloid from the brain, and they do so with different efficiencies. It has been shown that ApoE4 seems to be the slowest in removing beta-amyloid from the brain, which may be why it confers the most genetic risk.
In a previously published diet intervention, the researchers showed that a diet high in saturated fat content and with a high glycemic index worsened cerebrospinal fluid biomarkers of Alzheimer’s disease, lowered cerebrospinal fluid insulin levels, and worsened some aspects of memory function, whereas a diet low in saturated fat content and with a low glycemic index had opposing effects.
In the current study, 20 seniors with normal cognition and 20 with mild cognitive impairment, a precursor to Alzheimer’s disease, were studied. The patients were randomly assigned to diets that contained the same amount of calories but were either high or low in saturated fat. The high-saturated-fat diets had 45 percent of total energy coming from fat, and more than one-quarter of the total fat came from saturated fats. In the low-saturated-fat diets 25 percent of energy came from fat, with saturated fat contributing less than 7 percent to total fat.
After just one month, the diets caused changes in the amounts of amyloid beta and ApoE in the subjects spinal fluid such that there was more beta-amyloid present in those on the high saturated fat diet. This data is in line with previous studies showing a link between higher amyloid in the brain of patients with ApoE4 and diets high in saturated fat increasing the risk of developing Alzheimer’s. With the results of this study, there is a possible elucidation of the mechanism at play, namely that saturated fats decrease ApoE’s ability to remove beta-amyloid from the brain, leading to its increasing levels in the brain (and spinal fluid that bathes the brain). Further studies on modulating beta-amyloid and ApoE with diet are pending.
Thanks for reading,
Director, Memory Disorders Clinic
Associate Medical Core Director, Alzheimer’s Disease Cooperative Study
University of California San Diego
This post originally appeared in Alzheimer’s Insights, an ADCS Blog.
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