Vitamin D and Omega-3 fatty acids improve cognitive function and behavior in people with certain mental disorders, studies have shown. But scientists haven’t been sure how.
Now, researchers at Children’s Hospital Oakland Research Institute (CHORI) have come up with a possible explanation. After extensively reviewing the scientific literature, Dr. Rhonda Patrick and Dr. Bruce Ames tried to connect the dots to find what is responsible for linking two micronutrients—Vitamin D and Omega-3 fatty acids—to behavior and even to psychiatric disorders, such as schizophrenia and bipolar disorder.
The answer, they say, is serotonin, a chemical produced by our bodies that acts like a neurotransmitter, affecting cognitive functions and behaviors such as mood, decision-making, social and impulsive behavior. In fact, they say, clinical disorders like autism spectrum disorder (ASD), depression and attention deficit hyperactivity disorder (ADHD) have something in common: low brain serotonin.
Their study, published in the online version of Federation of American Societies for Experimental Biology Journal on February 24, describes the serotonin pathway, and the mechanism by which Vitamin D and Omega-3 fatty acids have an effect on serotonin production. “I came up with this general theory that Vitamin D and the Omega-3 fatty acids are all regulating the serotonin system,” said Patrick, who has a doctorate in biomedical science and whose areas of expertise are nutritional health, the brain and aging.
Patrick and Ames had already explained Vitamin D’s role in serotonin production in a previous paper published in 2014, in which they discussed the implications of finding that Vitamin D regulates how the essential amino acid called tryptophan converts into serotonin.
In the case of Omega-3 fatty acids, this is how it works, according to the current study: An Omega-3 acid called Eicosapentaenoic acid (EPA) increases serotonin release from presynaptic neurons. It does so by reducing proinflammatory-signaling molecules in our brain, called E2 series prostaglandins. Because these E2 molecules inhibit serotonin release, researchers believe that inflammation may have a negative impact on the amount of serotonin in the brain. “Since EPA is known to inhibit the generation of E2 series prostaglandins, it would allow for normal serotonin release in the presynaptic neuron,” Patrick said.
Another Omega-3 fatty acid that plays a role in the serotonin pathway is Docosahexaenoic acid (DHA). DHA influences the action of several serotonin receptors by increasing cell membrane fluidity in postsynaptic neurons, thus making them more accessible to serotonin.
But knowing how the serotonin pathway unfolds is just the beginning. The authors of the CHORI study also point out a problem. “Vitamin D, which is converted to a steroid hormone that controls about 1,000 genes, many in the brain, is a major deficiency in the U.S. and Omega-3 fatty acid deficiencies are very common because people don’t eat enough fish,” stated co-author Dr. Bruce Ames, director of CHORI’s Nutrition & Metabolism Center, in a press release.
Most of the people in United States (about 70 per cent) have low levels of Vitamin D, according to the National Health and Nutrition Examination Survey. Many Americans also have inadequate levels of Omega-3 fatty acids.
The human body produces Vitamin D when ultraviolet rays from the sun hit our skin directly. So not being exposed to the sun enough, using sunscreen, or even age and pigmentation factors may lead to low levels of this micronutrient in our body.
People mostly get Omega-3 by eating seafood. However, some people don’t eat enough fish, sometimes because they are concerned about mercury contamination. (A useful source to learn which commercial seafood products have lower levels of mercury is listed on the U.S. Food and Drug Administration’s website.
On top of possible nutritional deficiencies, people who have certain variations in serotonin-related genes might have a genetic predisposition to have low levels of serotonin, or they might metabolize it too fast. Having a nutritional deficiency of Vitamin D and Omega-3 in addition to a genetic predisposition “may push a person to precipitate mental illness or a brain dysfunction in general,” said Patrick.
The authors think that Vitamin D and Omega-3 fatty acid deficiency “may adversely affect behavior,” said Patrick. She said that this could manifest in small ways in some people with normal cognitive function, making them more irritable or anxious.
According to Patrick, brain serotonin has been shown to be low in autism, ADHD, bipolar disorder, schizophrenia and impulsive behavior disorders. “Other researchers have shown that depleting serotonin during early brain development leads to an abnormal brain structure and symptoms similar to autism in mice,” she said. The author also cites several studies that link autism incidence to maternal vitamin D insufficiency. In humans, Patrick said, Vitamin D deficiency during gestation has been shown to cause the same structural brain defects that are known to be associated with ASD, ADHD and schizophrenia.
The author said that there are still more studies to be done and pointed out the “obvious” limitations of their own study. “We haven’t done any randomized control trials giving fish oil supplements or Vitamin D supplements to people that have schizophrenia, or bipolar or depression,” to see if it would help improve their condition, for example, said Patrick.
“However,” she added, “other researchers have already shown this to be the case, and we just provided a plausible mechanism linking Vitamin D and Omega-3 to serotonin.”
“I don’t think most people think about food and how the food we eat affect our behavior,” said Patrick. She said people can take dietary supplements to help compensate inadequate levels of these micronutrients. However, Patrick said that it’s hard to make a recommendation about which supplements and how much of them a person should take. That is why getting a blood test to see if your levels are too low would be the best way to start, she said. “A blood test is very simple and they’re free; any primary care physician would do it,” she said. You can also order a kit online, added Patrick, who takes dietary supplements of both micronutrients and eats fish three times a week.
But too much Vitamin D in the body can be toxic for several reasons, said Patrick. And because there are many factors that control the ability of our skin to produce Vitamin D from the sun, the starting point should be a blood test.
Patrick said that Vitamin D supplements are cheap and that $20 might be enough to buy a monthly supply of Omega-3 pills, so she said it is possible for people to include this in their diet. “I think a lot of people out there are eating poor diets and that is depriving them of these important micronutrients,” she said.