DHA: nature's favorite semiconductor
I want to give you all a brief introduction to the compound docosahexaenoic acid (DHA), which I consider to be one of the most interesting fatty acids found in the human body. It's fairly well-known for being an anti-inflammatory agent, but it has some other fascinating properties that I rarely ever see discussed.
For those that are aren't familiar with DHA, it's what's known as an omega-3 fatty acid. Omega-3's are best known for being found in seafood and having anti-inflammatory properties. The other most well known besides DHA is EPA. You'll often see health experts/researchers, especially in the paleo community, refer to the need for a 1:1 ratio between omega-3's and another group known as omega-6
Omega-6 are conditionally inflammatory, acting as precursors for a group of compounds known as prostaglandins which can promote inflammation, but what few understand is that these are only produced when they are required (when inflammation is already present). Primarily omega-6 fats are used in production of structures like cell or neuron membranes. In fact, it's a common misconception that the brain is made up primarily of omega-3, it's actually almost entirely omega-6. Omega-6 fats are also funneled into production of arachidonic acid, which is used as a precursor for a number of signaling molecules that mediate everything from blood flow to inflammation.
The body needs a surplus of dietary omega-6, the 1:1 ratio is less important than the quality of the fats themselves. Let me explain what I mean by this. The primary source of omega-6 fats in the average American's diet comes from seed oils (corn, soy, canola, etc), which are found in fried and processed food. The high heat exposure these fats are exposed to damages their structure (polyunsaturated fats are very fragile), oxidizing them. In the body these fats only undergo oxidation in when the body drives up inflammation to fight off illness. When we consume fried/processed foods filled with these seed oils they create a massive inflammatory response, but the issue is the oxidation not the fats themselves. Many healthy foods contain natural levels of omega-6 fats that are stable and healthy for the body when not cooked/processed. Keeping a low ratio between omega-3 and 6 fats is still a good guideline to follow, but mostly because it requires you to keep a good surplus of DHA, so it doesn't have to be perfect.
So why is DHA so important in the brain?
Omega-3 fats also serve a number of functions in the body. They are most well-known for being potently anti-inflammatory, as they are metabolized into various ecosanoids that serve to modulate inflammation in the body. For example, when omega-6 fats are highly oxidized and inflammatory, omega-3's reduce this inflammation and vice versa. I could write an entire blog post on these effects, but today I want to focus on something a bit different.
In 500-600 million years of evolution, the function of DHA in the nervous system and eyes has never changed. Its analog DPA is more resistant to oxidative damage and easier to synthesize, yet for some reason all life has always evolved to use only DHA. This may seem mysterious, but mother nature always has her reasons.
First and foremost DHA has a very unique chemical structure. It is contains a long chain of alternating double and single bonded carbons, which looks something like this /\=/\=/\=/\=/\=/\=/\. If you compare this structure to omega-6 fats for example, their double bonds are spread out almost randomly. DPA only has 5 double bonds, so its alternation pattern doesn't span the full length of its carbon chain. This makes DHA very unique. Each of the double bonds in its structure is surrounded by a group of electrons known as a pi electron cloud. The /\'s in the structure are called methylene groups, and in this case they serve to separate the pi electron clouds, so they end up spread out slightly. Imagine this almost like a string of beads. This specific structure means that DHA acts as the perfect semiconductor!
Basically this means that when an electric current hits DHA, it travels along its chain through a process called “electron tunneling,” where the electrons spontaneously jump between each pi cloud. The highest concentration of DHA in the human body is found in the eyes, and the second highest in the brain. We'll get to the eyes in a moment, but in the brain DHA seems to actually play a role in the creation of memory! This works through an interesting mechanism. Neurons are loaded with DHA to allow them to conduct action potentials (electric signal bursts). Researcher Michael Crawford and his team found when fatty acids are turned over (recycled) in the nervous system, the more often-used pathways end up being strengthened by being loaded up with DHA. This process of building connections sounds an awful lot like how memories are formed!
Fats are typically stored in various forms, in the case of DHA often in molecules called glycerols. When we look at the evolutionary use of DHA we see another interesting pattern here, DHA is conserved in these lipids so that it always remains in the sn-2 position (second position). Once again, there's a reason for this, in this position DHA is paramagnetic. When a molecule is paramagnetic, this means it responds to magnetic fields. This also ties back to memory.
You may recall that when charged particles move, it generates a magnetic field. The body has a collective
magnetic field generated primarily by proton pumps in mitochondria, though other things like blood flow contribute as well. The charged currents in the nervous system may actually may actually generate a magnetic field as well. This happens on a low level, but adds up to a fairly large effect, the second largest magnetic field produced by the body is actually from the brain. Essentially this means when fatty acids in the nervous system are recycled, activated pathways will draw up DHA as a result of the magnetic fields they emit! It seems this process helps facilitate the complex network of electric impulse patterns we experience as memory.
Now what about DHA in the eyes?
To understand this first you need to understand the basics of vision. In some of my posts on twitter I've mentioned chromophores, compounds that absorb specific frequencies of light. Proteins in the body known as opsins are the chromophores that the body uses to sense light. Basically each opsin is structured to capture a specific frequency of light. Each opsin is bound to the compound retinal, which is actually a modified active form of vitamin A. Retinal's molecular structure has a long side chain that normally sits bent at an angle. However when light hits it, it excites retinal's electrons, straightening the chain and setting off a signal into the nervous system. The opsins each retinal molecule is bound to capture only certain frequencies of light, allowing the nerve pathways to be separate by wavelengths and colors.
Now remember that the highest concentration of DHA in the human body is in the eye. It acts as a buffer around the rods and cones, and helps conduct the electric impulses put off by opsins/retinal. It has a unique property that allows this to occur. The bond mechanics are too complex for this blog to cover, but to put it simply, DHA's bond configuration acts as an on/off switch. When one of its electrons is excited (by light or electric impulse), the configuration flips from one side of the structure to the other, then reverts back to its previous state, re-releasing the energy. DHA acts as a molecular conveyor belt for the electrons released from photoreceptors, carrying them into the nervous system. Phosphatidylcholine and phosphatidylethanolamine help direct electrons from photoreceptors into DHA.
Interestingly, retinal, opsins, and DHA are also found spread across the skin as well. They still make up
photoreceptors, but instead of being plugged into the brain the way eyes are, they read the body's light environment to regulate the peripheral circadian clock in cells/mitochondria. These receptors in the skin regulate everything from melatonin production to energy metabolism. Unfortunately artificial light derails this process, and this is one of the biggest reasons why artificial light is so toxic.
As I've mentioned elsewhere, artificial light contains only a fraction of the visible light spectrum, mostly blue light, with no UV or infrared light. In sunlight blue light is paired with infrared-A which renders it non-toxic. However in isolation, blue light damages cells, blocking the electron transport chain, and causing a huge increase in free radical production. When blue light hits photoreceptor cells, it breaks apart the retinal and opsins, and the oxidative stress it creates breaks down both retinal and DHA. In the skin this results in dysregulation of the circadian mechanism, creating a cascade of effects that can result in leptin and insulin resistance, and set the stage for numerous disease states. In the eye blue light contributes to myopia and other types of ocular degeneration. Carboxyethylpyrrole, the compound formed when DHA is oxidized is actually used as a marker for the severity of macular degeneration.
I hope I've given you a greater appreciation for the miracle of molecular semiconduction that is DHA. If this hasn't motivated you to eat loads of seafood I don't know what will. I'll leave you with this:
Despite what your optometrist might tell you, most of the time it's actually possible to recover from issues like myopia. However, doing so requires management of inflammation and oxidative stress, especially avoiding blue light. A surplus of dietary omega-3's is also essential, as it reduces inflammation and give the body building blocks to rebuild the eye. Retinol, the active form of vitamin A, is also essential as it's converted into retinal. Eating liver once or twice a week and seafood almost daily will give you a healthy surplus of both. Given the raw material's your body will do most of the work, if you want to repair your eyesight all that's left from there is gradually tapering your prescription strength. There are many taper plans for this online, this is my personal favorite: