These conversations are always fun and strong heated opinions from each side. As always the truth lies somewhere in-between the extremes.
In this conversation we cover starch causing excessive serotonin and endotoxemia; carnivorism and the lack of fiber; long term implications of low/zero fiber diets on cancer risks and restoration of the microbiome.
Research is consistent that fiber supplements and high-fiber diets strengthen the integrity of the intestinal barrier and promote the growth of beneficial bacteria in the microbiome, both of which reduce the creation and absorption of endotoxins into circulation. In contrast, a high-starch diet, particularly one rich in flours and other refined carbohydrates, strongly promotes endotoxin synthesis.
A fiber-fed microbiome creates serotonin that is used locally by the intestines to increase peristalsis and help move food through the digestive tract. Some of this serotonin enters into circulation and can have peripheral effects, but the relevance of these effects remains controversial. None of the serotonin affects neurotransmission within the brain, though, because it can’t cross the blood-brain barrier.
Low- and zero-fiber diets are consumed by many under the correct notion that fiber isn’t an essential nutrient. However, the essentiality of a nutrient for survival is irrelevant to its essentiality for optimal long-term health.
Animal data and biologic mechanisms strongly support the notion that prolonged low- and zero-fiber diets cause the eventual extinction of beneficial microbes, breakdown of the intestinal mucosal lining, and causes a deficit of butyrate that all facilitate intestinal inflammation and cancer. Blood ketones cannot make up for intestinal butyrate deficit because the receptors (GPR109A) that benefit intestinal health exist within the intestinal tract. Also, “animal fibers” and other protein-containing fermentable compounds do not produce beneficial metabolites; they facilitate the growth of pathogenic bacteria and lead to the synthesis of carcinogenic and genotoxic compounds.
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