The certainty of evidence for all outcomes in this systematic review is rated as low to very low by GRADE due to high heterogeneity, suspected publication bias, and imprecision, meaning the observed lack of difference between plant and animal protein cannot be confidently interpreted as true equivalence.

Different proteins break down into different amino acid patterns, and the body uses these patterns differently depending on how much of each amino acid is available and how fast it gets there. When studies mix different types of plant and animal proteins with varying amino acid profiles and digestion speeds, the body's response becomes unpredictable. This makes it look like both types of protein do the same thing, but the real difference is hidden because the studies don't control for these biological variations.