Hello readers! I apologize for the lack of posts- I’ve been devoting my spare time to a novel I’ve been writing, as well as a number of grant applications. One of them is for an NIH R21 for Project: Cancer-Fighting Gut Bacteria.
Earlier this week I experienced a bout of food poisoning, and at the same time an intensification of symptoms associated with my bipolar disorder. This made me think of the articles I had been posting on this site and once I recovered, and looked through my notes for Project: Cancer-Fighting Gut Bacteria, I realized that I needed to find more articles on probiotics and whether they establish in the gut, as well as whether they have any beneficial effects on diseases of the gastrointestinal tract, and how they work.
The results of this search, which I conducted over several hours tonight, have been fruitful! I share with you the URLs for three of the most accessible articles I have come across.
First of all, an older article but a good one that’s been cited more than 400 times: Probiotics: determinants of survival and growth in the gut. Essentially, the take home message is that, while probiotics can have beneficial effects on controlling things like diarrhoea, and can survive transit of the stomach into the lower GI tract, there’s no evidence they actually establish in the intestines- they seem to exert their effects while passing on through. This suggests that in order to get a beneficial effect from probiotics, you might have to keep taking them consistently.
Here’s a newer article on the same subject: A Meta-Analysis of Probiotic Efficacy for Gastrointestinal Diseases. This article summarizes research from a lot of other articles, all studies of the effects of probiotics on different diseases. The take-home message is that, for most probiotic bacterial strains and diseases, taking probiotics can help- but there are some diseases that are not as well treated, and some bacterial strains that are less effective. Quoting from the abstract, “Six of the eight diseases: Pouchitis, Infectious diarrhea, Irritable Bowel Syndrome,Helicobacter pylori, Clostridium difficile Disease, and Antibiotic Associated Diarrhea, showed positive significant effects. Traveler’s Diarrhea and Necrotizing Enterocolitis did not show significant effects of probiotcs. Of the 11 species and species mixtures, all showed positive significant effects except for Lactobacillus acidophilus, Lactobacillus plantarum, andBifidobacterium infantis.” The last sentence is important, since L. acidophilus is typically found in yogurts, and if this is the only strain in your probiotic preparation, or the main strain, it might not be as effective as you’d like against a disease. There still may be other health benefits, just not necessarily control of disease.
A very useful article with a lot of really nice figures that explain in detail how probiotic bacteria exert their effects on you (it might be a bit too technical, but it is open access so there’s no harm in taking a look) is this one: Effects of probiotics on gut microbiota: mechanisms of intestinal immunomodulation and neuromodulation. It talks a bit about the gut-brain axis, which is of particular interest to me (especially this week, given my health issue from earlier), and it also talks about how gut bacteria can affect your immune system. There also is a bit of discussion of how dietary compounds (like histidine, glutamate, and dietary fibre) lead to the production of compounds that affect your metabolism (like short-chain fatty acids (important for colon health), gamma-aminobutyric acid (GABA, a neurotransmitter) and histamine (influences inflammation and immune responses).
I apologize for being absent from this blog for so long and I hope you enjoy these articles- all are or should be open access, but if you have problems accessing any of them write to me and I will see if I can help you find a PDF.