One should not pit proteins against fiber: for optimal intestinal comfort, it is advisable to combine these two nutrients, because an excess of protein not compensated for by fiber leads to less favorable bacterial fermentation in the colon.

noli's read

The principle of differentiated digestion presented is scientifically accurate: proteins are primarily assimilated in the small intestine, while fiber nourishes our beneficial microbes further down. A landmark intervention study (RCT) published in Nature by David et al. (2014) demonstrated that an exclusively animal-based diet (high in protein, lacking fiber) rapidly alters the microbiota profile and increases protein fermentation byproducts. Furthermore, a research review (synthesis of evidence) by Windey et al. in the European Journal of Nutrition confirms that excess protein reaching the colon generates compounds such as ammonia or hydrogen sulfide. Although the exact long-term impact of these compounds on overall digestive well-being still requires further observational studies, the synergy described is very real. The suggestion to diversify one's diet by combining proteins and plant-based fiber is therefore particularly sound for supporting both one's cells and microbes.

the sources

No named source held this one up — that absence is part of the verdict.