https://www.thecut.com/2018/02/i-accidentally-made-myself-lactose-intolerant-with-whole30.html https://www.thecut.com/2018/02/i-accidentally-made-myself-la...

https://www.thecut.com/2018/02/i-accidentally-made-myself-lactose-intolerant-with-whole30.html https://www.thecut.com/2018/02/i-accidentally-made-myself-la... quoted "gastrointestinal specialist Kim Barrett, a professor of medicine at the University of California, San Diego" > “To some extent, our ability to handle lactose is a use-it-or-lose-it phenomenon,” Barrett says. The body digests lactose — a disaccharide — by using lactase, an enzyme in the small intestine, to break it down into the monosaccharides glucose and galactose, which can then be absorbed. “If you don’t have the [lactose] substrate in the diet, you start to reduce the synthesis of the lactase enzyme to digest it,” Barrett explains. “After a period of completely excluding lactose from the diet, you may not have any of those digestive enzymes present.” Maybe unawareness here is a gender thing? I have heard this story too many times from women doing weird short-term restriction diets (or going vegan and trying to undo) to feel like I need "current science" to "support" the very fact that it happens. Many things can happen because of genes or other reasons.