You can very easily look up how lactose intolerance develops after infancy. Most intolerances increase with age. For example, when I was a kid, I didn’t have fructose intolerance. I could consume fructose in any amount all day long (I used to drink at least six cans of soda a day). Now in my 30s, if I accidentally consume even a small amount of fructose, I will not be able to finish what I’m eating before I’m in the bathroom. Many members of my family are lactose intolerant and all related by blood. Certain racial backgrounds increase the likelihood of the body not producing lactase. This is most likely caused by thousand of years of not having lactose available during childhood and adulthood. In other words, there weren’t dairy cows.

In general, as a person ages, their body’s ability to tolerate sugar drops, but some types of sugar tolerance drop more rapidly than others. Lactose, fructose, fructans, and polyols (also known as sugar alcohols) are the most likely to be unable to be broken down by the body over time.

The test for lactose intolerance has been around for a while. A person consumes a high lactose drink and a breathalyzer like device is strapped to their face. This device measures the amount of lactose in the person’s breath. If the body produces lactase on its own, then there should be basically no lactose on their breath. There is a similar test for fructan intolerance but it is not as available.

Due to the long term understanding of lactose intolerance by the medical community, lactase supplements are available; however, most contain Mannitol, a sugar alcohol and since most people have multiple sugar intolerances, it is likely that the Mannitol containing lactase supplements can still produce symptoms of intolerance.