Almonds: little effect on the gut microbiota

There is no doubt, diet is the most effective means of modulating the composition of our gut microbiota. But studies are often limited to one nutrient (the effect of a protein, fiber, etc.) without evaluating the effect of the whole foodstuff. Well, all nutrients in a foodstuff interact, with antagonistic and synergistic effects, so much so that in real life, the overall effect of a foodstuff is rarely the sum of the individual effects of each of its components. Thus, almonds, as all seeds, are rich in lipids and therefore in calories (incidentally oil is extracted from them!) but also in fibers which act on intestinal transit, in polyphenols with anti-aging properties, etc.

To evaluate the effects of almonds on the gut microbiota, American almond producers have just funded a study which represents, in terms of quality, the Holy Grail in nutrition: a randomized (sidenote: Randomized trial study in which the products tested (here: whole almonds / powdered almonds / muffins) are distributed randomly, between the participants.   ) controlled trial (sidenote: Controlled trial study in which a subset of the participants receives a placebo or a known product (here muffins) and allows a comparison to be made. ) . Thus, 87 young volunteers little inclined to eat fruit and vegetables were distributed randomly between 3 comparable groups. Their mission: to consume, every day for 4 weeks, two snacks in place of their usual snacks, comprising either 2 handfuls of whole almonds, or the equivalent in ground almonds, or 2 muffins with the same calorie content (controls).

Disappointing results, limited health benefits

The least that can be said, is that the results observed will not have matched the level of investment. The authors hoped to observe that the almonds had a boosting effect on the intestinal bifidobacteria (sidenote: Bifidobacterium A genus of Y-shaped bacteria, most species of which are beneficial to humans. They are found in the gut of humans, and in some yogurts.

They:
- Protect the gut barrier 
- Participate in the development of the immune system and help fight inflammation 
- Promote digestion and improve symptoms of gastrointestinal disorders Sung V, D'Amico F, Cabana MD, et al. Lactobacillus reuteri to Treat Infant Colic: A Meta-analysis. Pediatrics. 2018 Jan;141(1):e20171811.  O'Callaghan A, van Sinderen D. Bifidobacteria and Their Role as Members of the Human Gut Microbiota. Front Microbiol. 2016 Jun 15;7:925. Ruiz L, Delgado S, Ruas-Madiedo P, et al. Bifidobacteria and Their Molecular Communication with the Immune System. Front Microbiol. 2017 Dec 4;8:2345. ) . Well, rather the opposite happened... They wagered on an accelerated intestinal transit due to the fibers present in the almonds: but no, the oily nuts changed nothing. The study even called into question a principle accepted up until then by nutritionists, namely that, unlike finely ground almonds, whole almonds would continue, even after mastication, to retain the lipid droplets in their structure. Well, the results show that the commercial grinding of almonds produces practically no differences in terms of lipid accessibility. In other words, your body will be able to assimilate the fats and calories of whole almonds, practically as well as those of ground almonds.

The exception: a short-chain fatty acid

Only one positive note was observed: the consumption of almonds (whole and ground) led to a significant increase in the production, by the gut bacteria, of a short-chain fatty acid (sidenote: Short chain fatty acids (SGFA) Short chain fatty acids are a source of energy (fuel) for an individual’s cells. They interact with the immune system and are implicated in communication between the gut and the brain.   Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020;11:25. ) beneficial to our health, butyrate.