Dietary Maillard reaction products are partially degraded by human gut microbiota, with N-ε-fructosyllysine being fully metabolized into lysine and lactic acid by lactic acid bacteria, indicating that certain Maillard reaction products function as microbial substrates rather than inert waste.

When food is cooked at high temperatures, sugars and proteins stick together to form complex molecules that survive digestion. These molecules reach the gut intact, where certain bacteria break them apart to extract lysine and turn the sugar parts into lactic acid. This process feeds beneficial bacteria that make healthy acids, while reducing the growth of harmful bacteria that produce toxic gases.