Lactose

Topic summary contributed by volunteer(s): Jessica

Lactose is a sugar molecule found in milk. This molecule is composed of glucose and galactose.

Lactose Intolerance

Many people cannot tolerate lactose past infancy, leading to symptoms of poor digestion such as bloating.

Lactose is often an ingredient in placebos, called sugar pills, used in clinical trials. If not taken into consideration, lactose intolerance in participants can affect test results. For example, a study of 84 people who avoid gluten and/or wheat (due to beliefs about their inability to digest those compounds), found that some were actually unable to tolerate fructose or lactose.

Lactose and Bone Health 

Lactose and galactose have been studied in relation to milk’s purported effect on bone health. Elevated levels of galactose in the blood, as occurs in people with galactosemia, a deficiency that prevents the appropriate digestion of galactose, is associated with bone loss, even in children. And galactose has been used to cause premature aging in lab animals, leading to shortened lifespans, oxidative stress, inflammation, and brain degeneration.

These findings may help to explain why milk consumption has actually been associated with an increased risk of mortality in both men and women, as well as an increase in fracture rates in women. Such findings have not been associated with the consumption of soured milk and yogurt; however, this may be because the bacteria in these dairy products ferment some of the lactose, thereby reducing the negative effects of lactose and galactose.

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