Galactose is present in our environment in only very small quantities and is found mainly in dairy products in the form of lactose (glucose + galactose). Most baby mammals, including humans, are adapted to survive on lactose when they are young, but lose the ability to digest it as they mature (and start eating solid foods).

About 70% of the world’s adult human population are lactose intolerant and cannot digest lactose or use it for energy production. People with ancestry in Northern Europe, the Middle East and India (the places where people have the longest association with domesticated cattle) have a version of the lactose digestion gene which is not disabled when they grow up. Those people (most of the Australian population) are able to continue to drink and eat milk products into adulthood. Those of us who can digest galactose will convert it to glucose and treat it as glucose for all important digestive purposes.

Everybody else lets it pass straight through the digestive system, which is why a primary symptom of lactose intolerance is diarrhea. Galactose is slightly less sweet than glucose but still on the sweet side of the palate. If you are not lactose intolerant, pay close attention to the next glass of milk you consume. You will notice an ever so slight sweet tinge to the flavor and it is certainly not sour (at least if you drink it before the ‘use by’ date).

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