According to a study that is published in PLoS Medicine’s Special Issue on Dementia shows that low levels of polyunsaturated fatty acids in the brain may speed up the development of Alzheimer’s disease. It is therefore vital not to shy away from dietary fats. What is important, however, is to consume unspoiled sources of omega-3 and omega-6 fatty acids in the proper balance. Polyunsaturated fatty acids have numerous functions in the brain, on which our nervous system, cardiovascular system, memory, learning ability, and lingual skills depend.
Alzheimer’s disease is the second leading cause of dementia. More than 46 million people worldwide suffer from the disease, which is predicted to affect 131.5 million people in 2050. Alzheimer’s disease causes the neurons in several areas of the brain to perish, and researchers have found a buildup of two large proteins called tau and beta-amyloid. There are also studies that point to imbalances in the cerebral neurotransmitters and insulin resistance of the brain that leads to energy starvation of the neurons. In any case, Alzheimer’s disease is a slowly progressing disease that normally leads to death after 7-10 years. As a preventive measure, it is therefore vital to make sure that the brain is properly supplied with essential, polyunsaturated fatty acids, where omega-3 and omega-6 play a particularly important role.
Sources of the different fatty acids
Saturated: Animal fat, dairy products, coconut oil
Monounsaturated (omega-9): Olive oil, rapeseed oil
Polyunsaturated (omega-6): Most plant oils
Others types of polyunsaturated (omega-3): Oily fish contains EPA/DHA. Linseed oil contains ALA.
The omega-3 fatty acids DHA and EPA have particularly many functions in the brain
The human brain mainly consists of fats such as cholesterol, omega-3, and omega-6. The different fats are important for the structure and function of the cell membranes. The cell membranes are responsible for dispatching signals that initiate or stop the different activities that the cells need to carry out in the brain and other parts of the body. In epigenetics, the cell membrane is actually regarded as the brain of the cell.
The omega-3 fatty acid, DHA, that represents 11% of the brain’s dry weight, contributes to cell membrane pliability, and it enhances NOS (nitrogen oxide synthase) activity that is important for memory and learning.
DHA is also important for the structure of neuroprotectin D1 (NPD1), a substance with many functions in the brain.
DHA and EPA even function in a biochemical interplay with the omega-6 fatty acid, arachidonic acid, and the balance between them is vital. For instance, EPA competes with arachidonic acid to produce some hormone-like substances called prostaglandins that regulate inflammation, insulin sensitivity etc. Therefore, it is vital to consume omega-3 and omega-6 in the right balance.
Did you know that around 60% of the brain’s dry weight consists of fats like cholesterol, omega-3, and omega-6?
Brains affected by Alzheimer’s disease lack unsaturated fatty acids
It has been known for more than two decades that Alzheimer’s disease is associated with a buildup of the two large proteins, tau and beta-amyloid. However, there is limited knowledge about how these proteins are produced and in what way they speed up the development of Alzheimer’s disease.
In the above-mentioned study that was carried out at King’s College London and National Institute on Aging in the United States, researchers compared brain tissue samples from 43 people in the age group 57-95 years. They looked at differences between hundreds of small molecules in the following three groups:
- people with healthy brains
- people with elevated levels of tau and beta-amyloid protein (who had not yet encountered memory problems)
- people who had been diagnosed with Alzheimer’s disease
The scientists also looked at different parts of the brain with different tendencies to produce tau and beta-amyloid proteins, in combination or individually. The found that brains affected by Alzheimer’s disease had significantly lower content of unsaturated fatty acids compared with healthy brains. According to lead investigator, Dr. Cristina Legido Quigley from King’s College London, the study revealed that lack of unsaturated fatty acids plays a vital role in the development of Alzheimer’s disease. The researchers also found to their big surprise that levels of DHA increased in the affected areas of the brain, as the disease progressed. Still, they warrant more research before confirming this observation, which contradicts earlier findings.
Fish, fatty acids, and Alzheimer’s disease
Several earlier studies have shown that levels of DHA in the brain of people with Alzheimer’s disease are lower than in healthy individuals. Also, people with Alzheimer’s disease have lower levels of DHA in their red blood cells, and as the disease progresses, levels of DHA in the blood decrease. The amount of DHA in red blood cells is also related the amount of DHA in brain cells.
In a famous study from Rotterdam in Holland, 5,385 people aged 55 years and older were followed for a little over six years. This study demonstrated that a high fish intake helped prevent dementia, particularly Alzheimer’s disease.
In another study, the diets and health of 1,416 people aged 68 years and older were monitored for seven years. It turned out that eating fish or shellfish at least once a week was linked a 34% lower risk of dementia and a 31% lower risk of Alzheimer’s disease. Fish contains quite a lot of EPA and DHA, which we humans can easily absorb and utilize. As mentioned earlier, these fatty acids are of great importance to the structure and function of the brain. Furthermore, EPA helps to counteract inflammation and regulate insulin sensitivity, which are also believed to affect the development of the disease.
Finally, fish contains important antioxidants like selenium and zinc that counteract oxidative stress and cell destruction caused by free radicals.
How omeag-3 fatty acids counteract Alzheimer’s disease
Skewed balance between omega-3 and omega-6 in modern diets
Omega-3 and omega-6 are essential fatty acids that we humans are unable to produce and therefore need from our diet in adequate and carefully balanced amounts. Today, farmed fish, slaughtered cattle, chickens, and dairy cattle are all given feed with a higher omega-6 content. Therefore, fish, meat, eggs, and dairy products typically contain less omega-3 than these foods used to. All of these factors combined - the animal feed, our decreased consumption of fish, and increased consumption of ready meals and margarine – cause us to get too much omega-6 and too little omega-3. Modern diets in Western countries often have a skewed balance between the different essential fatty acids, creating a 10:1 or even 30:1 ratio between omega-6 and omega-3 – where the optimal balance is 4:1 or even less.
Omega-3 fatty acids from fish or supplements?
Most of us do not follow the official dietary recommendations to eat fish several times a week. We should ideally consume at least 350 grams of fish, including 200 grams of oily fish that are particularly rich in EPA and DHA. For those who dislike the taste of fish, fish oil supplements are an obvious solution. Fish oils based on free fatty acids ensure good absorption in the digestive system. Always make sure to choose a fish oil supplement that complies with the health authorities’ threshold values for peroxide levels and levels of environmental toxins.
King´s College London. Alzheimer´s disease linked to the metabolism of unsaturated fats. ScienceDaily March 22, 2017
Stuart G Snowden et al. Association between fatty acid metabolism in the brain and Alzheimer’s disease neuropathology and cognitive performance: A non-targeted metabolomic study. PLoS Medicine 2017
Bruce H. Lipton. Intelligente celler. Borgen 2009
Olle Hagelund: Omega-3 revolutionen. Medhag AB 2012
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