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Tuesday 20 June 2017

Intestinal bacteria determine dietary choices

Ground-breaking research reveals that we have less control over what we want to eat than we perhaps think. Who decides what is put on the table? It appears that intestinal bacteria play an important role in this.

 

Neuroscientists have proven for the first time that intestinal bacteria “talk” to the brain about what should be eaten. The study was published on the 25th of April of this year in PLOS Biology. The researchers found two types of intestinal bacteria that have a direct effect on the nutritional needs and dietary choices in animals.

 

Interaction between nutrients and microbiome

It is becoming increasingly clear that the interaction of nutrients with the microbiome has a unique impact on our health. Take, for example, L-carnitine, that in the past was sometimes linked to heart problems. In fact, it isn’t L-carnitine that causes problems, but the gut flora: certain non-beneficial intestinal bacterial convert L-carnitine found in red meat into the harmful substance trimethylamine (TMAO). Are there also more favourable interactions?

 

Yes, definitely, it has been found that the health benefits of cacao, for example, are not solely in the cacao bean. Cacao is fermented by Bifidum to form anti-inflammatory polyphenols, which have a beneficial effect on cardiac health. Fermentation can be stimulated by eating a piece of fruit, say the researchers. But can the intestinal bacterial also stipulate what they want to eat? According to the study in PLOS Biology, they can indeed.

 

Increased need for protein

Experiments show that a deficiency in certain amino acids in fruit flies results in poorer fertility and an increased need for protein-rich food. It doesn’t matter which amino acid is omitted. The researchers then tested the effect of omission on five different types of bacteria that occur in fruit flies in the wild.

 

It was found that there are two types of intestinal bacteria that could reverse the increased need for protein in fruit flies. This adaptation in the microbiome possibly results in the fruit flies being more capable of adapting to unfavourable circumstances.

 

Talking to the brain

Initially, the researchers thought that the bacteria would make up for the fruit flies who lacked amino acids. But the experiments didn’t reveal this. The intestinal bacterial “appeared to cause a change in the metabolism that has a direct effect on the brain and the body. Because of this, the brain thinks that protein saturation has occurred”, say the researchers.

 

The mechanism of action has not yet been clarified. The specific intestinal bacteria are also present in people, but there is a much wider variety of species. The research shows in any case that the gut flora has a much greater influence on our physical and psychological condition than we thought.

 

Sources

  1. Amar Sarkar et al, Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals, Trends in Neurosciences (2016)
  2. https://www.acs.org/content/acs/en/pressroom/newsreleases/2014/march/the-precise-reason-for-the-health-benefits-of-dark-chocolate-mystery-solved.html
  3. Koeth R.A. et al., Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis, Nature Medicine 19, 576–585 (2013).
  4. Leitão-Gonçalves R, Carvalho-Santos Z, Francisco AP, Fioreze GT, Anjos M, Baltazar C, et al. (2017) Commensal bacteria and essential amino acids control food choice behavior and reproduction. PLoS Biol 15(4): e2000862
  5. Seiler S.E. et al., Carnitine Acetyltransferase Mitigates Metabolic Inertia and Muscle Fatigue during Exercise, Cell Metabolism, Volume 22, Issue 1, pp. 65-76, 7 July 2015.
    1. Timothy G. Dinan, Catherine Stanton, and John F. Cryan, Psychobiotics: A Novel Class of Psychotropic, Biological Psychiatry, Volume 74, Issue 10 (November 15, 2013)
    2. Wei-Kai Wua, b, Suraphan Panyoda, Chi-Tang Hoc, Ching-Hua Kuod, Ming-Shiang Wub, Lee-Yan Sheena, Dietary allicin reduces transformation of L-carnitine to TMAO through impact on gut microbiota, Journal of Functional Foods, Volume 15, May 2015, Pages 408–417.