|One major problem with all the "gut microbiome"-research is that we're still having a hard time predicting the health outcomes of specific changes in the total and relative numbers of bacteria.|
With the publication of the latest study from the Institute of Disease Control and Prevention at the Academy of Military Medical Sciences in Beijing this changed - even if the title, "Metabolic shifts and structural changes in the gut microbiota upon branched‑chain amino acid supplementation in middle‑aged mice" (Yang. 2016) doesn't say anything positive.
I guess, I don't have to tell you about the importance of gut microbiota to human health. After all, the 'gut bugs' have gained extensive attention not just in the medical community, but also in the media lately. I myself have written repeatedly about the human microbiome and its contribution to our health.
It's likewise no news for you that the composition of your gut microbiome is heavily influenced by environmental facturs - including and first and foremost your diet - including your supplements like BCAAs. In their latest study, the Chinese researchers wanted to get to the bottom of previously reported beneficial and ill effects of BCAA supplements and planned a study. A study in which male BALB/C mice were housed identically, received identical diets and exercise, but different drinking water. In that, the mice were randomly assigned to two groups: (1) unsupplemented (control, n = 9) and (2) supplemented with BCAAem (in drinking water; 1.5 mg/g body weight per day) beginning at 11 months of age (n = 9).
|Figure 1: The BCAAem supplement contained (in %): leucine 31.3; lysine 16.2; isoleucine 15.6; valine 15.6; threonine 8.8; cysteine 3.8; histidine 3.8; phenylalanine 2.5; methionine 1.3; tyrosine 0.7; and tryptophan 0.5 (Yang. 2016).|
What do I make with the decrease in Enterobacteriaceae - Is that good or bad news? Pitout et al. (2008) have called Enterobacteriaceae an "emerging public-health concern" due to their recently discovered links to bloodstream infections that occur in response to urinary tract infections with one of the nasty multidrug-resistant Enterobacteriaceae (mostly Escherichia coli). The answer to the previously posed question, whether that's a good or bad thing should thus be easy to answer: a good one.To get to the bottom of effects, the gut microbiomes of the mice were analysed by 16S rDNA sequencing. Quantitative polymerase chain reaction was performed to identify Bifdobacterium spp. in the gut, and gas chromatography–mass spectrometry was conducted for faecal-metabolite detection - all to find out whether a BCAA-rich EAA mix would work any "magic" on the mouse gut - magic that could explain the metabolic effects scientists observed in previous studies.
|Figure 2: OUT numbers for specifc bacterial groups (Yang. 2016).|
Do BCAAs work only for older people? They, for sure, seem to work best in old mice. It is thus obvious to assume that it will be old human beings, where they're the most useful. Also, if you scrutinize the data in the paper you will see that each of the beneficial effects occured only late in the life of the rodents, i.e. from month 11-15.How's that? Well, it was not completely surprising that the results showed that "the structure of the gut microbiota changed, and BCAAem-supplementation in mice slowed the change speed of gut microbiota which is due to age" (Yang. 2016): a result that is in line with the age-specificity of many of the benefits of BCAAs scientists have observed in both human and rodent studies, where similar high BCAA amino acid products have been shown to help conserve lean mass and/or even extend the life of smaller animals - in a similar way as caloric restriction does. This doesn't mean that the other changes Yang et al. recorded were irrelevant, though: "
This doesn't just include the buffered decrease in total bacterial numbers, but also the changes of the gut make-up of which - if we are honest - we'd have to say that they were not exactly positive when the animals were younger. After all, the highest level of the allegedly "good" bifidobacteria was observed in the control, not the BCAA group, and changes in the "bad" (that's relatively certain for once) LPB occured exclusively in the old mice, too.
|Bifidobacteria DNA counts improved only in aged mice, too (Yang. 2016)|
"In addition, the abundance of the Akkermansia and Bifdobacterium increased in BCAAem-supplemented mice, while the ratio of Enterobacteriaceae decreased in BCAAem-supplemented mice" (Yang. 2016).These changes in the bacterial make-up of the lab animals, namely increases in the numbers of bacteria which are generally considered "healthy" and decreases in the numbers "unhealthy" enterobacteriaceae, could just as well (or even more likely) be responsible for the differences in a literal dozen of metabolites, representing sugar and lipid metabolism, the scientists observed when they compared the metabolome in the guts of the supplement to the control group.
|Figure 3: Serum LBP concentrations in the two groups at 11 and 15 months (Yang. 2016).|
- Pitout, Johann DD, and Kevin B. Laupland. "Extended-spectrum β-lactamase-producing Enterobacteriaceae: an emerging public-health concern." The Lancet infectious diseases 8.3 (2008): 159-166.
- Yang, Zhan, et al. "Metabolic shifts and structural changes in the gut microbiota upon branched-chain amino acid supplementation in middle-aged mice." Amino Acids (2016): 1-15.