The Inuit Are Genetically Resistant to Ketone Production
sciencedirect.com
sciencedirect.com
"Inuit metabolism revisited: what drove the selective sweep of CPT1a L479?"
"Yet seminal studies carried out on Inuit subjects in the early twentieth century yielded surprising results from a metabolic perspective. Low ketone bodies in the breath and urine were observed in the fed state [17,18,23]. These metabolic results contrast with that which is often registered among healthy non-Inuit subjects, who tend to show a marked rise in ketone levels in the breath and urine when consuming a very low carbohydrate diet [24,46]. These results suggest that the traditional Inuit diet may not actually be ketogenic, as commonly assumed, despite being very low in carbohydrate. More intriguingly, in three studies undertaken by Heinbecker in the 1920s and 1930s, breath and urinary levels of ketones in the fasted state were also found to be lower than in non-Inuit subjects [17,47,48]. The fasted state usually corresponds both to a high rate of fatty acid oxidation, indicated by a low respiratory quotient (RQ), and a high production of ketone bodies (see [6]). Similarly, the consumption of fat in the absence of protein and carbohydrate also encourages a high rate of fatty acid oxidation and is expected to result in a low RQ and high production of ketone bodies. The respiratory quotients in the fasted state in Inuit subjects [17], and after ingestion of pure fat [23] were found to be lower than those of non-Inuit subjects, indicating very efficient fatty acid oxidation, but with levels of ketone bodies that were much lower than expected. The detection of low RQs in combination with low ketone bodies were interpreted by Heinbecker to indicate a difference in the metabolism of the Inuit subjects from subjects of non-Inuit descent, which allowed them to oxidize fatty acids efficiently without producing the expected levels of ketone bodies [17,49]."