Gut microbiota and mental illness

I have been arguing on this blog that supplements have to be available in the gastrointestinal tract as well as systematically for supplements to be helpful. There has been a growing realization that what happens in the gut can have a huge impact on mental health. See these reviews Microbes and mental health: A review; Harnessing Gut Microbes for Mental Health: Getting From Here to There and Brain-Gut-Microbiota Axis and Mental Health.

If supplements are not available in the gastrointestinal tract this cannot but affect gut microbiota differently compared to supplements that are available in the gastrointestinal tract. I am open to the possibility that differences in gut microbiota can play a big role in mental states, however, the gut could also be set up so the gut has to use nutrients when nutients first pass through the gut. Use of nutrients by the gut could be a necessary first step in the use of nutrients systematically.

There is a lot of talk about how the diet of our very distant ancestors is the diet that is appropriate for us. One thing is certain about the diet of our very distant ancestors. Our very distant ancestors did not take nutrients than were formulated not to be available in the gut.

Only taking supplements that are available in the gut, when taking supplements, is one way to address to address gut microbiota positively. As an example EPA + DHA combinations are frequently supplied in enteric coated softgels to avoid ‘fishy smells’. However, biting on the softgels, swallowing the contents and then throwing the softgels away works much better for depression. And what is more even given EPA + DHA work in clinical trials EPA + DHA will not work in the field as EPA + DHA supplements sold in stores are very frequently enteric coated.

DHA and Alzheimer’s disease

Docosahexaenoic acid (DHA) levels are low in Alzheimer’s disease. DHA is synthesized from alpha-linoelic acid which is an essential fatty acid which must be obtained from the diet. For DHA to be synthesized from alpha-linoelic acid, alpha linoleic acid must first be absorbed.

A meta-analysis indicates that homocysteine levels are significantly high in Alzheimer’s disease. High homocysteine levels in Alzheimer’s disease indicate the transsulfuration pathway is dysregulated in Alzheimer’s disease as homocysteine is not being metabolized to L-cysteine which is what the transsulfuration pathway does.

With low levels of L-cysteine there will be low levels of taurine. Taurine is synthesized from L-cysteine. Taurine is needed for the formation of bile acids which are needed for fat absorption. With alpha-linoelic acid not absorbed in Alzheimer’s disease due to low levels of taurine synthesis of DHA will be impaired in Alzheimer’s disease which is what is seen is Alzheimer’s disease. Effectiveness of supplementation with DHA in Alzheimer’s disease could be limited due to a failure to absorb DHA due to low levels of taurine in Alzheimer’s disease.

Taurine only poorly crosses the blood-brain barrier. However, to assist with essential fatty acid absorption taurine does not have to cross the blood-barrier. Taurine by enhancing fat absorption can enhance brain function.

Homotaurine has has been shown to be a promising therapy for Alzheimer’s disease. In Alzheimer’s disease taurine could be taken with with fatty acid supplements high in alpha linoelic acid, such as lignan free flax seed oil. Lignans are polyphenols so flax seed oil with lignans is avoided.