The link between plant fibre & saturated fat
The link between plant fibre & saturated fat
A brief lesson in digestion and nutritional tunnel vision.
When humans eat plant foods, the fibrous components (cellulose) travel all the way down our digestive tract (mouth—oesophagus—stomach—small intestine…) remaining relatively unchanged, until they reach the penultimate stop—the large intestine / colon.
In the large intestine, cellulose is transformed into something useful
Not by human cells, by our microbiome.
Our gut microbes feed on the cellulose, and as a by-product of their metabolism, produce fats, called Short Chain Fatty Acids (SCFAs).
SCFAs may then be absorbed through the intestinal wall, and utilised throughout the body in a variety of ways.
Those that remain in the colon become a key source of nutrition for the intestinal (human) cells.
SCFAs play essential roles in human physiology
For example;
Metabolic health [2]
Brain health [5]
Gut health [6]
Immune function [6,7]
This is, in part, why plant fibre is recommended as part of a healthy diet.
Nobody seems to be arguing against the utility of SCFAs.
But here’s a few things that might raise your eyebrows.
What you haven’t been told about SCFAs…
Our gut microbes are not herbivorous—there are multiple foods (not just cellulose) for the SCFA-producing microbes in our gut [1,3,4,8].
Many foods (like butter, parmiggiano reggiano…) already contain SCFAs [5] but we’re told to avoid these because they contain saturated fat.
Meanwhile, SCFAs are saturated fats!
🤔
Recap
We’ve been told for many years to eat lots of vegetables, rich in plant fibre, in order to fuel (microbial) production of SCFAs, which are essential to our health.
But at the same time, we’re told to avoid foods that already contain SCFAs, like butter, and raw cheese, because they contain saturated fat.
Meanwhile, these essential SCFAs are saturated fats.
And as it turns out, our microbes can make them from other foods too—not just plant fibre.
🤯
References
[1]
Depauw, S, Bosch, G, Hesta, M, Whitehouse-Tedd, K, Hendriks, WH, Kaandorp, J & Janssens, GPJ 2012, ‘Fermentation of animal components in strict carnivores: A comparative study with cheetah fecal inoculum1,2’, Journal of Animal Science, vol. 90, no. 8, pp. 2540–2548.
[2]
Hernández, Canfora, Jocken, & Blaak 2019, ‘The Short-Chain Fatty Acid Acetate in Body Weight Control and Insulin Sensitivity’, Nutrients, vol. 11, no. 8, p. 1943.
[3]
Louis, P & Flint, HJ 2017, ‘Formation of propionate and butyrate by the human colonic microbiota’, Environmental Microbiology, vol. 19, no. 1, pp. 29–41.
[4]
Stevens, CE & Hume, ID 1998, ‘Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients’, Physiological Reviews, vol. 78, no. 2, pp. 393–427.
[5]
Stilling, RM, van de Wouw, M, Clarke, G, Stanton, C, Dinan, TG & Cryan, JF 2016, ‘The neuropharmacology of butyrate: The bread and butter of the microbiota-gut-brain axis?’, Neurochemistry International, vol. 99, pp. 110–132.
[6]
Trompette, A, Pernot, J, Perdijk, O, Alqahtani, RAA, Domingo, JS, Camacho-Muñoz, D, … Marsland, BJ 2022, ‘Gut-derived short-chain fatty acids modulate skin barrier integrity by promoting keratinocyte metabolism and differentiation’, Mucosal Immunology, vol. 15, no. 5, pp. 908–926.
[7]
Wastyk, HC, Fragiadakis, GK, Perelman, D, Dahan, D, Merrill, BD, Yu, FB, … Sonnenburg, JL 2021, ‘Gut-microbiota-targeted diets modulate human immune status’, Cell, vol. 184, no. 16, pp. 4137-4153.e14.
[8]
Zhao, J, Zhang, X, Liu, H, Brown, MA & Qiao, S 2018, ‘Dietary Protein and Gut Microbiota Composition and Function’, Current Protein & Peptide Science, vol. 20, no. 2, pp. 145–154.