‘Gut health’ has become the darling of the wellness movement. A Google search for the phrase threw up the following:
On the one hand, I’m pleased that so many people are becoming interested in learning more about the vital role that their gastrointestinal tract, and its teeming community of microscopic inhabitants, has on their health and well being.
But on the other hand, I’m also concerned that – as with just about every other health-related issue – individuals and businesses have quickly jumped onto the public’s growing interest in gut health in order to exploit it commercially by convincing people that in order to have a well-functioning gut, they simply need to buy a product or program, or eat particular ‘”gut healing” foods and avoid those that are the “worst foods for your gut”, as the screenshot of my Google search of “gut health” clearly illustrates.
The reality, as always, is far more complex, multifactorial and nuanced than this reductionist, dumbed-down – but commercially lucrative – version of “gut health” implies.
Let’s take a close look at the gap between the popular version of ‘gut health’ and what the science actually shows, focusing on just one of the innumerable factors that impact on our gut microbiome and its habitat, the human intestinal tract: dietary fat intake.
Popular websites such as this one sing the praises of so-called ‘healthy fats’, nominating extra virgin olive oil, virgin coconut oil, MCT oil, tallow (rendered animal fat), lard (rendered pig fat), grass-fed butter and ghee as the best fats to include in your diet to heal your gut. Notably, all of these fats and oils aside from olive oil are extremely high in saturated fat:
- Coconut oil: 87% saturated fat
- MCT oil: 100% saturated fat
- Tallow: 50% saturated fat
- Lard: 32% saturated fat
- Butter: 70% saturated fat
- Ghee: 65% saturated fat
Scientists who actually study the effect of dietary fat on the health of the gut microbiota, and the gut itself, have a somewhat different take on the issue of dietary fat.
High dietary fat intake has been linked with a plethora of destructive effects on the gut and other body systems, including:
- Reduced diversity of intestinal bacteria
- Increased intestinal permeability (‘leaky gut’)
- Low-grade, chronic inflammation and unfavourable changes in immune system activity.
Gut researchers single out saturated fat – found mostly in animal products, but also abundant in tropical plant oils and fats including coconut and palm oils and cacao butter – as the most destructive type of fat, as it is the most potent at triggering leaky gut and associated inflammation.
How do high fat diets, especially those abundant in saturated fat, do some much damage to our gut?
Firstly, we don’t absorb all the fat that we consume. Even in healthy people who are eating a fairly typical amount of fat, around 7% of dietary fat traverses the small intestine and reaches the colon relatively intact, promoting the growth of bacteria in the Firmicutes phylum and reducing the abundance of Bacteroidetes; this altered Firmicutes:Bacteroidetes ration is associated with obesity, since Firmicutes harvest more energy from our food than Bacteroidetes.
Secondly, saturated fat forms a ‘raft’ that transports lipopolysaccharide (LPS) derived from Gram-negative bacteria inside our gut right through the gut wall and into the capillaries that wrap around our gut, and from there into our systemic circulation.
Increased LPS in our blood circulation is called ‘metabolic endotoxaemia’ and it triggers low grade inflammation, which has been linked to metabolic syndrome, depression, and even a type of brain damage which makes it hard for overweight people to lose weight.
And thirdly, a high fat diet increases the amount of bile secreted into the small intestine, which results in more bile arriving in our colon. Bile-eating bacteria such as Bilophila wadsworthia thrive on this excess bile, generating compounds that promote inflammation, cause leaky gut, impair glucose metabolism and aggravate fatty liver.
The hydrogen sulphide gas produced by bile-eating bacteria also aggravates visceral hypersensitivity, an abnormal sensitivity to the distention and contraction of the gut which underlies irritable bowel syndrome (IBS) and other functional gastrointestinal pain syndromes.
The bottom line is that if you’re looking for guidance on how to improve your gut health, you need to be highly discriminating with your information sources. Popular websites, blogs, YouTube channels and other media sources frequently promote misinformation that can seriously endanger your health.
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