It is common knowledge that omega-3 fatty acids are vital for our brain development and nervous system. Now, researchers from Harvard Medical School in the United States have discovered that they also play an important role in maintaining the blood-brain barrier that protects the central nervous system against bacteria and toxins.
The human brain is the superior organ of our nervous system. Around 20% of the blood that pumps through the body reaches the brain. The blood-brain barrier protects us against bacteria and toxins. This barrier, essentially an impermeable membrane in the inner layer of the blood vessels, keeps our brain tissue separate from the blood. Water-soluble substances such as salts have great difficulty with passing through the blood-brain barrier, while other essential water-soluble substances like glucose (blood sugar) and amino acids are able to move across the membrane with help from special transport mechanisms. Lipid-soluble substances like fats, alcohol, narcotics, and various medical drugs are able to pass through the blood-brain barrier with comparatively little effort. The barrier has a very important physiological function, which is to protect the brain and make sure to maintain a constant chemical composition in the brain that provides optimal condition for brain cell functioning.
Lipids are a group of molecules that include fats, fatty acids, lipid-soluble vitamins (vitamins A, D, E, and K), among other things. Lipids are able to pass through the blood-brain barrier rather easily, and they have a structural function in the cell membranes, they signal, and they store energy.
Omega-3 fatty acids are a part of the protective bubbles
Professor in neurobiology, Chenghua Gu, and his team of researchers from Harvard Medical School have shown for the first time ever how the blood-brain barrier remains closed by suppressing a specific process known as transcytosis, where molecules are carried into the cells in small “bubbles”. The researchers also observed that the production of these “bubbles” is suppressed by a lipid transport protein called Mfsd2a, which carries the omega-3 fatty acid, DHA, into the cell membranes. In other words, Mfsd2a and the omega-3 fatty acid, DHA, both contribute to sealing off the blood-brain barrier and protecting the brain tissue by suppressing transcytosis and the small bubbles with bacteria and toxins.
The omega-3 fatty acids also work closely together with omega-6 fatty acids. Having the right balance between these two types of fatty acids is vital for the cell membranes and their ability to signal and absorb molecules.
In our part of the world, however, many people consume far too much omega-6 at the expense of the omega-3 fatty acids, which may leave the blood-brain barrier increasingly vulnerable.
The blood-brain barrier protects against many bacteria and toxins
As mentioned, the blood-brain barrier protects against bacteria and toxins. The different types of bacteria and toxins may originate from the body’s natural microflora (via leaky mucosa), from our metabolism, and from contaminants and various sources of environmental pollution. It is essential for the blood-brain barrier to have such a profound protective effect on the central nervous system. Therefore, it is vital to keep the brain well supplied with omega-3 fatty acids, where oily fish contribute with the two important omega-3 types, EPA and DHA. Omega-3 fatty acids are also found in linseed oil and other vegetable sources but in the form of ALA (alpha-linolenic acid), which many people have difficulty with converting into EPA and DHA because of sluggish enzymatic processes.
Envisioning new strategies to help more medicine across the blood-brain barrier
The blood-brain barrier, as mentioned earlier, can also be a hindrance for many medical drugs, as it prevents the active compounds from reaching the brain. However, in blocking the Mfsd2a transport protein, the scientists envision a new strategy that may help more medicine across the blood-brain barrier inside the small “bubbles”. This may open the door to the treatment of several diseases such as brain tumors, Alzheimer’s disease, and stroke.
Published in the journal, Neuron, the new study is the first to show, at a molecular level, how slowing down transcytosis (the formation of small “bubbles” inside the nervous system) helps the blood-brain barrier’s natural protection of the brain.
According to Professor Chenghua Gu, we still have a lot to learn about the regulation of the blood-brain barrier. Nonetheless, greater insight in the different mechanisms may enable us to manipulate them in such a way that future drugs can be much more effective.
There is even evidence to suggest that a sufficient intake of the omega-3 fatty acid, DHA, helps prevent diseases of the brain that involve the presence of bacteria or toxins.
Omega-3 fatty acids – fish or supplements?
Most people fail to follow the official diet guidelines that recommend eating fish several times per week, preferably at least 350 grams (with 200 grams coming from oily fish types that are particularly rich in EPA and DHA.) People who dislike the taste of fish can easily take a fish oil supplement, instead. Fish oil supplements based on free fatty acids are easily absorbed in the body. It is also important to choose a product that is within the threshold values for peroxides and environmental toxins.
How much omega-3 do we need?
International research recommends the following intake
- 500 mg to prevent an actual deficiency
- 1 gram for proactive support – e.g. for the brain and cardiovascular system
- 2-4 grams for intensive support – e.g. for aching joints and inflammation
Did you know that you get about 1 gram of omega-3 from a herring fillet and 3-4 grams from a salmon steak?
Benjamin J et al. Blood-Brain Barrier Permeability Is Regulated by Lipid Transport-Dependent Suppression of Caveolae-Mediated Transcytosis. Neuron 2017
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