Gut health is paramount to good health.  Imbalances in the gut microbiome have been correlated with immune dysfunction, brain dysfunction, diabetes, and increased risk of autoimmunity.  It appears that we can add to that list cardiovascular disease.  New research at the University of Nottingham suggests that lower diversity of gut bacteria correlates with hardening of the arteries.  How do we create more diversity in our microbiome?  According to most of the research on the microbiome, one key is having a very diverse diet.  Another is avoiding antibiotics, which of course is sometimes unavoidable.  The probiotic world is constantly changing, but there is increasing evidence that soil-based probiotics may be the most effective since they are the best at withstanding hydrochloric acid in the stomach and they tend to colonize the intestines for a longer period of time.  More information about soil-based probiotics can be found at https://microbiomelabs.com/.

Reference:

https://academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehy226/4993201

In case you didn't see my facebook post, a recent study published in April, 2018, in the journal Nutrients, showed a correlation between garlic, celery, and gluten intake and major depressive disorder (MDD).  

http://www.mdpi.com/2072-6643/10/5/548

Related to that, what I believe is a significant change in food sensitivity testing is the company Alcat doing two Yale University studies reflecting the usefulness of this test.  Here are the links to the studies:

https://www.businesswire.com/news/home/20180413005438/en/Simple-Inexpensive-Blood-Test-Predict-Foods-Trigger
https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/s12986-018-0260-4

http://bmjopengastro.bmj.com/content/4/1/e000164

Since we're about to enter influenza season, anything that might reduce the risk or severity of the flu is pertinent.  According to a recent study done at Washington University School of Medicine, there are reasons why some people have more severe flu symptoms than others.  One reason they discovered was that certain gut microbes need to be present in order to process immune-supporting substances from our diet.  One such substance is a flavonoid, as discussed in this particular study.  So, the take-home message is, if you want to reduce the risk of severe flu, optimize healthy gut microbe levels and consume flavonoid rich foods such as berries, apples, and tea.

Also keep in mind that Vitamin D has been shown to protect against colds and flu, as confirmed in a recent study published in the British Medical Journal in 2017.

Sources:

Washington University School of Medicine. "Natural compound coupled with specific gut microbes may prevent severe flu: Mouse study reveals how gut microbes fight influenza." ScienceDaily. ScienceDaily, 3 August 2017. <www.sciencedaily.com/releases/2017/08/170803141048.htm>.

Washington University School of Medicine. (2017, August 3). Natural compound coupled with specific gut microbes may prevent severe flu: Mouse study reveals how gut microbes fight influenza. ScienceDaily. Retrieved August 7, 2017 from www.sciencedaily.com/releases/2017/08/170803141048.htm

Washington University School of Medicine. "Natural compound coupled with specific gut microbes may prevent severe flu: Mouse study reveals how gut microbes fight influenza." ScienceDaily. www.sciencedaily.com/releases/2017/08/170803141048.htm (accessed August 7, 2017).

Small intestinal bacterial overgrowth (SIBO) is a newer diagnosis that means bacteria from the colon have migrated into the small intestine.  The most common symptoms are bloating and irregular stools, and it is usually diagnosed with a hydrogen breath test.  It can be caused by excessive starch intake and apparently food poisoning (such as campylobacter). 

Most fascinating to me is the possible correlation being made between SIBO and other diseases, such as:

Multiple Sclerosis:

Parkinson's:

https://www.ncbi.nlm.nih.gov/pubmed/27589873
Atherosclerosis (hardening of arteries):

https://www.ncbi.nlm.nih.gov/pubmed/28275304
Pancreatic diseases:

SIBO may be caused by poor gallbladder function, involving poor bile flow:

Levothyroxine (synthetic thyroid T4 medication) might cause SIBO, according to this study:

H. Pylori may contribute to SIBO (methane production):

Previous studies have suggested that people with schizophrenia may have lower levels of GABA in the brain.  Remember that GABA is the primary calming neurotransmitter in the brain, while glutamate is the primary excitatory neurotransmitter in the brain.  Newer research supports the idea of low GABA in those with schizophrenia.  GABA is available as an over the counter supplement, and taking vitamin B6 supports the conversion of glutamate to GABA in the brain.  If you have schizophrenia, you might consider talking to your Doctor about GABA and B6 supplements.

Source:

Karolinska Institutet. "Major research project provides new clues to schizophrenia." ScienceDaily. ScienceDaily, 14 March 2017. www.sciencedaily.com/releases/2017/03/170314081539.htm.

Multiple sclerosis involves degeneration of the myelin sheath, a protective layer on nerve cells.  Most treatments for MS involve trying to stop the progression of the disease, but few have attempted to promote regeneration of the myelin.  Scientists have recently discovered that cells within the immune system, called Regulatory T Cells (T-reg cells for short), promote the growth of new myelin within the nervous system.  Therefore, it would seem beneficial (there does not appear to be any data on this yet though) to support the production of T-reg cells.  While doing research on that, I found an article that suggests a role in this regard for vitamin A, vitamin D, and probiotics.  The article also discussed the potential benefit of avoiding gluten.  That article can be found here:

In another article about what supports T-reg cells, folic acid was mentioned, along with green tea extract:

Source:
http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.4528.html

Regulatory T cells promote myelin regeneration in the central nervous system. 

Nature Neuroscience 2017 doi:10.1038/nn.4528         

A double blind, placebo controlled, randomized trial published in the American Journal of Clinical Nutrition (Am J Clin Nutr March 2017 vol. 105 no. 3 758-767) showed that specific probiotic strains were beneficial for the symptoms of seasonal allergies.  Specifically, two forms of bifidobacterium and one form of lactobacillus were supplemented.  The mechanism of action is unclear, but I would assume that having more beneficial bacteria has a balancing effect on the immune system overall. 

Source:

A study at the University of Alabama at Birmingham looked at the balance of bacteria in those with Parkinson's disease and essentially found higher levels of certain bacteria and lower levels of other specific bacteria compared to people who don't have Parkinson's.  This was reported by Science Daily, March 2, 2017.  My interpretation of the main points made in the article:

-Humans have more than 1000 species of bacteria in the gut.

-The first sign of Parkinson's disease is often gut symptoms.

-This study involved 197 people with Parkinson's compared to 130 controls.

-Those with Parkinson's have an imbalance in the gut microbiome.

-An important function of the microbiome is to detoxify environmental pollutants.  This may be very important considering that those with Parkinson's often have previous exposure to pesticides and herbicides.

Source:

University of Alabama at Birmingham. "Link between microbiome in the gut, Parkinson's discovered." ScienceDaily. ScienceDaily, 2 March 2017. <www.sciencedaily.com/releases/2017/03/170302133859.htm>.

A new study done at McMaster University and published in Science Transational Medicine showed that gut bacteria not only have an influence on intestinal function, but also brain function.  Researchers transplanted fecal material from humans with and without IBS-D (irritable bowel syndrome with diarrhea) into mice. 

From Science Daily (March 1, 2017):

"The researchers found that aspects of the illness that were impacted through fecal transplants included gastrointestinal transit (the time it takes for food to leave the stomach and travel through the intestine); intestinal barrier dysfunction; low grade inflammation; and anxiety-like behavior."

I find it particularly interesting that they mention intestinal barrier dysfunction, otherwise known as "leaky gut" or intestinal permeability.  This is an obvious mechanism by which gut bacteria, or more specifically, endotoxin from gut bacteria, can reach and influence the brain.

The authors also mentioned that since evidence suggests that intestinal bacteria alter brain function, they may also play a role in disorders such as Autism, Parkinson's, and Multiple Sclerosis.

From a causal perspective, then, optimizing the health of the intestinal tract, including the bacterial balance and intestinal barrier function, should be a consideration when looking to optimize brain health. 

Sources:

Transplantation of fecal microbiota from patients with irritable bowel syndrome alters gut function and behavior in recipient mice. Science Translational Medicine, 2017; 9 (379): eaaf6397 DOI: 10.1126/scitranslmed.aaf6397

McMaster University. "Intestinal bacteria alter gut and brain function, study shows." ScienceDaily. ScienceDaily, 1 March 2017. <www.sciencedaily.com/releases/2017/03/170301142503.htm>.

A potential game changer of a study was done at Seattle Children's Hospital and published in the Journal of Clinical Gastroenterology in December of 2016.  The study tested the Specific Carbohydrate Diet (SCD Diet) in pediatric patients with crohn's disease and/or ulcerative colitis.  With nothing other than dietary changes, at the end of the 12 week study, 8 of the 10 participants were apparently in clinical remission. The diet also had a significantly positive impact on microbial balance in the stool (it reduced harmful bacteria).  The SCD Diet is quite restrictive in that it does not allow most starches, sugars, and dairy (some exceptions), but it does allow things like most meats, eggs, vegetables, fruits, home made yogurt, and honey.  If you have intestinal bowel disease, consider discussing this diet with your Doctor.

For more information about the diet, this site is an excellent resource:

Sources:

Seattle Children's Hospital. "Novel diet therapy helps children with crohn’s disease and ulcerative colitis reach remission." ScienceDaily. ScienceDaily, 28 December 2016. www.sciencedaily.com/releases/2016/12/161228171130.htm.

http://journals.lww.com/jcge/Abstract/publishahead/Clinical_and_Fecal_Microbial_Changes_With_Diet.98120.aspx