How Can Neurotrophins Affect Gut Inflammation? (BDNF)

Exercise

Moderate exercise (and improved physical fitness) is among the best remedies for gut inflammation and overall health. According to many studies, physical activity actually changes the composition of the gut flora, resulting in an increase of beneficial species. Multiple studies have also found that an exercise regimen improved IBS symptoms specifically [R].

The key may be to ensure that physical exertion remains within your (or your intestines’) comfort zone. Vigorous physical activity, such as extensive running, may stress the intestines, leading to so-called “runners’ trots.” However, moderate physical activity appears to improve transit time and help regulate bowel movements [R].

Fortunately, exercise is also one of the best ways to increase BDNF. In sedentary male college students, high-intensity exercise boosted BDNF. Likewise in 50 obese or overweight people, exercise and weight loss increased circulating BDNF [R, R, R].

Stress Reduction

Psychological stress is widely believed to trigger or worsen IBS. In fact, some researchers refer to both “irritable bowel” and “irritable brain” as equal factors in the development of IBS. Furthermore, anxiety and frustration with gut symptoms can further worsen these same symptoms. As such, many experts recommend stress management strategies as part of a holistic strategy to manage and treat this condition [R, R, R].

People who are under a lot of stress also produce less BDNF. Furthermore, chronic or acute stress and cortisol decrease BDNF in the rat hippocampus and prefrontal cortex [R, R, R, R].

Meditation

One specific stress reduction technique with evidence to support its use in IBS is meditation. In a study of 75 IBS patients, mindfulness meditation significantly reduced reported IBS symptoms. In two studies of a total of 232 patients, a type of relaxation training similarly reduced symptom severity, in some cases significantly better than conventional therapies [R, R, R].

Meanwhile, in a study of 38 people, participating in a 3-month yoga and meditation retreat significantly increased circulating BDNF in the blood [R].

Exercise and stress reduction have been found to reduce IBS and increase BDNF in clinical settings. Meditation may be a helpful stress reduction technique for this purpose.

Probiotics

One of the most likely causes of IBS is dysregulation of the gut flora. In fact, individuals with IBS often appear to have decreased diversity and numbers of beneficial microbiota and protective strains such as L. reuteri [R].

Probiotic supplements are therefore promising strategies for managing IBS. Multiple probiotic species have produced promising clinical results, including:

• Bifidobacterium infantis [R]
• Bifidobacterium lactis [R]
• Bacillus coagulans [R]
• Saccharomyces cerevisiae (Brewer’s yeast) [R]

Fermented foods are a great way to increase your intake of diverse probiotic bacteria without the use of supplements. Consuming fermented milk products (which include buttermilk, cheese, yogurt, kefir, sour cream, and more) significantly improved symptoms of IBS in multiple clinical trials [R, R].

Another fermented food with promise for IBS is sauerkraut (a type of fermented cabbage) [R, R].

Healthy gut flora also produce butyrate, a compound that is absorbed by the colon. Butyrate may help increase BDNF production, though this relationship has only been directly observed in rats [R]. 

Fiber Supplements

Another way to help improve the gut microbiota is through the use of fiber supplements. Resistant starches and other fibers that feed healthy gut bacteria have been found to improve IBS in multiple clinical studies; furthermore, these gut bacteria produce butyrate, which may increase BDNF [R, R, R, R, R].

A meta-analysis of psyllium and other strategies in IBS found that patients taking psyllium were more likely to report symptom improvement than those taking a placebo. Furthermore, the number of adverse events associated with psyllium husk was determined to be insignificant [R].

As a galactomannan polysaccharide, guar gum is fermented for energy by healthy gut flora. As such, guar gum may promote the growth of beneficial bacteria in the gut, thereby suppressing IBS [R, R, R].

Eating a diet rich in wheat bran (30 g per day) was found to decrease abdominal discomfort and improve bowel habits in 188 IBS patients. However, the wheat bran diet was not as effective as guar gum, and fewer patients reported satisfaction with wheat bran than with guar gum [R].

Increased butyrate in the colon has been found to improve IBS symptoms and increase BDNF expression. Probiotics and fiber supplements are two possible ways to increase butyrate production by beneficial gut bacteria.

Berberine

Berberine is a compound found in several different plants, including Barberry (Berberis vulgaris), Oregon Grape (Mahonia aquifolium), Goldenseal (Hydrastis canadensis), and Chinese goldthread (Coptis chinensis). It has a 3000-year history of use in traditional Chinese and Indian medicine [R].

In one study of 196 patients with IBS-D (diarrhea predominant), those who received berberine hydrochloride reported less diarrhea, abdominal pain, and urgent defecation than those who took the placebo. Furthermore, the patients’ quality of life appeared to improve, based on surveys intended to measure anxiety and depression [R].

We currently don’t know whether berberine has any effect on BDNF in humans. However, in mouse and rat studies, berberine has been found to up-regulate BDNF throughout the nervous system and particularly in the hippocampus region of the brain [R, R, R].

Berberine improved IBS-D symptoms in one clinical trial, but its effect on BDNF in humans has not been studied.

Curcumin

Curcumin, a polyphenol found in turmeric, is one of the most popular natural anti-inflammatory supplements on the market. In multiple small clinical studies, curcumin reduced the symptoms of IBS; however, placebo-controlled trials are lacking [R, R].

There is currently no clinical research on the effect of curcumin on human BDNF. In cell studies, however, direct contact with curcumin increased BDNF expression. Curcumin has low bioavailability, but once it is in the bloodstream it can cross the blood brain barrier, making it a target for future development as a therapeutic agent [R, R, R].

There is a well-established link between psychological stress and IBS, and when appropriate, doctors may prescribe antidepressants to patients with both IBS and mental illness. Certain antidepressants have also been observed to gradually increase BDNF expression over time. This observation further reinforces the potential role of BDNF in IBS [R, R, R].

If you have both persistent IBS and mental illness (depression or anxiety, in particular), your doctor may consider prescribing antidepressants. Do not under any circumstances take these drugs on your own, without a doctor’s prescription.