The question is backwards. Lactose intolerance in adults is not a disease to be cured, it is the natural default of humans. 2/3 of adult humans are lactose intolerant. If you transplant a lactase producing organ like the small intestine it will continue to produce lactase. I doubt any reputable surgeon would do such a transplant.
Lactose intolerance isn’t actually a fault, it’s how our bodies come by default. We *should* be intolerant to lactose. We don’t naturally drink milk into adulthood.
Humans that drank cows milk over many generations eventually developed a tolerance to lactose, but even people that are lactose tolerant can develop intolerance by simply not drinking any milk for an extended period of time.
There’s two forms of lactose tolerance – genetic and environmental.
Young children are almost always lactose tolerant, in that their bodies produce lactase. Most people have a gene that stops us from producing lactase after a certain age. You can be genetically lactose tolerant if you don’t have the gene that disables lactase production. Human breast milk contains lactose, and producing lactase is not without cost, so you can see why we would have evolved to produce lactase but only in early childhood.
Environmental lactose tolerance is generally obtained from gut bacteria. Shifting your gut bacteria balance can be done with probiotics and drinking milk, feeding the bacteria that eat lactose. Gaining this tolerance can be an unpleasant process. Farmers often have environmental lactose tolerance.
Finally, you can take lactase tablets a while before consuming lactose.
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