— particularly the healthy ones found in fish
— either protect against or accelerate the risk of Alzheimer’s disease.
Dietary fats are either saturated or unsaturated. Saturated fatty acids come from meat, dairy products, pastries, and cookies. Monounsaturated fatty acids are found mainly in olive oil. The main polyunsaturated fatty acids (PUFAs) include n-6 (linoleic acid) and n-3 (alpha linolenic acid, docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]. The main sources of n-6 PUFA are vegetable oils and primary sources of n-3 PUFA are fatty fish, such as mackerel, salmon and tuna. They are also known as omega-
3 fatty acids, or simply omega-3s.
Our cholesterol levels are greatly impacted by dietary fat. It is long known that an elevated blood cholesterol level is linked to the development of Alzheimer’s. Moreover, one of the most important genetic risk factors for Alzheimer’s, apolipoprotein E epsilon 4, is the key cholesterol transporter in our brain. In a meta-analysis on the role of dietary fatty acids in dementia, researchers concluded the following:
— An increase in saturated fatty acids has a negative impact on cognitive functions.
— High consumption of PUFAs, weekly fish consumption, and monounsaturated fatty acid intake reduce the risk of age-related cognitive decline
— Among older adults in southern Italy, high intake of unsaturated fatty acids and antioxidant compounds and low intake of saturated fats improved their cognitive functions
Those n-3 fatty acids come exclusively from eating fish. DHA is part of the brain’s cell membrane. A small amount of DHA is synthesized from alpha-linolenic acid and EPA; the former from vegetable oils and nuts and the latter from fish. It has been known for years that n-3 PUFAs act in many positive ways on the brain. One review article came to some key conclusions amongst people in Chicago and Rotterdam:
— Higher total consumption of the n-3 fatty acids was associated with a much lower risk of Alzheimer’s
— DHA, but not EPA, was responsible for this reduced risk
— Alpha-linolenic acid intake was only linked with a lower Alzheimer’s risk in certain people
— One study failed to find any association between total intake of n-3 fatty acids and risk for Alzheimer’s
Overall, here are my recommendations: Starting at midlife, try to limit the consumption of foods high in saturated and trans unsaturated fats (e.g. red meat, baked goods, ice cream, butter, margarines with partially hydrogenated oils). And be sure to eat at least one fish meal a week.
Read my previous article in this series: