2. Vitamin D Is an Important Gene Regulator
To understand why vitamin D plays such an important role in brain function (and dysfunction), it’s important to understand what vitamin D actually is. Despite being named a “vitamin,” vitamin D actually gets converted into a steroid hormone (other steroid hormones include estrogen and testosterone).
As a steroid hormone, it regulates over 1,000 different physiological processes, and controls around 5 percent of the human genome. Dr. Michael Holick, who’s a leader in vitamin D research, thinks it may even control twice that amount of genes.
When you have enough vitamin D in your body, it binds to vitamin D receptors located throughout your body, thereby acting like a key that opens the proverbial door.
The vitamin D receptor complex can go deep inside the DNA, where it recognizes the tell-tale sequence of code that instructs the vitamin D receptor complex to either turn the gene on (making it active), or off (making it inactive).
Emerging evidence suggests those little tell-tale sequences are present in as much as 10 percent of all genes, but according to Patrick, it hasn’t been empirically proven that vitamin D has the ability to activate or deactivate all of those genes.
She agrees it’s quite likely that this might be the case though, which gives vitamin D a truly profound influence.
Autism Has Risen in Tandem With Vitamin D Deficiency
While autism is not likely caused by any one factor, it’s worth noting that as autism incidence has gone up, so has vitamin D deficiency.
“There’s that correlation between autism incidence rising and vitamin D deficiency rising, largely as a consequence of people wearing sunscreens, and staying indoors more … UVB radiation is very important to make vitamin D in the skin,” Patrick notes.
“What my research identified when I was at Children’s Hospital Oakland Research Institute (CHORI) with Dr. Bruce Ames, is that one of the genes vitamin D regulates encodes a for an enzyme called tryptophan hydroxylase (TPH).
TPH is responsible for converting tryptophan (which is a rare amino acid you get from the protein that you eat) into serotonin.
Most people associate serotonin with being a neurotransmitter in the brain that regulates your mood. It’s important for feeling good. But actually it does so much more in the brain during brain development and also throughout the rest of the body.”
Gut Versus Brain Serotonin
You have two different tryptophan hydroxylase genes in your body — one in your brain (TPH2), and one in your gut (TPH1).
The one in your brain makes serotonin in the brain, and the one in your gut converts tryptophan into serotonin in the gut, and, contrary to popular opinion, the latter CANNOT cross the blood-brain barrier to get into your brain.
This is an important point, because while many understand that the majority (about 90 percent) of the serotonin in your body is produced in the gut and not the brain, the thinking has been that the gut serotonin will automatically influence serotonin in the brain.
Since it’s unable to cross the blood-brain barrier, this is not the case. The two serotonin systems are completely separate.
Your gut serotonin does serve an important function though, as it plays a role in the ability of a specific type of blood cell called platelets to respond to tissue injury On the other hand, it can also cause trouble, by promoting inflammation.
As explained by Patrick:
“The serotonin made in the gut gets taken up by your platelets. Platelets can’t make their own serotonin, so they need to get it from the serotonin that’s made in the gut.
It plays a very important role in causing platelets to aggregate together, which is important when you injure yourself. If you cut yourself you want to have that coagulation … to form a clot, so that you don’t bleed out. Serotonin plays an important role in making sure that platelets do that.
You need to make serotonin in your gut. But on the other hand, it’s a double-edged sword, because too much serotonin in the gut actually causes gut inflammation. The reason it does that is it also activates immune cells in your gut called T-cells, causing them to proliferate.
They can start firing away pro-inflammatory cytokines … It’s been shown that if you stop mice from producing serotonin in the gut, it completely takes away their gut inflammation. It resolves very robustly.”
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