The vegan diet has no taurine and very little of its ultimate precursors, methionine and cysteine.
Taurine is necessary to make the stronger bile acids, the taurocholates and the taurochenodeoxycholates. Given taurine deficiency in bile producing liver cells at the very sites where synthesis is taking place, the liver will make more glycocholates and glycochenodeoxycholates. Look for the level of glycine bile acid derivatives vs taurine bile acid derivatives in stool and in urine as markers of local taurine deficiency in bile-producing liver cells.
The vegan diet has low fat, high fat soluble nutrients, no taurine, and little methionine and cysteine. How then to make much taurine-containing bile acids to solubilize, digest and absorb essential fats, conditionally essential fats, and fat soluble nutrients? Could vegans be deficient in essential fats (as measured by underpowered mitochondrial respiration), conditionally essential fats (any fats they are unable to synthesize sufficient quantities of), and fat soluble nutrients? Could vegans be deficient even in vitamin K, even though consuming so much of it in green leafy vegetables? Could they be deficient in vitamin A, E, and D as well as various carotenoids (some of which are clearly not vitamin A precursors) and other useful fat soluble substances?
How odd this all is.