Blood Glucose Data Analysis
INTRODUCTION
Although we can easily digest milk as babies, most of us lose this ability as adults. This is because we usually stop
producing lactase, an enzyme that breaks down the main sugar in milk. However, about one-third of people
worldwide still produce lactase as adults. In this activity, you will learn about a test for whether someone is likely
to produce lactase. This test is based on the amount of a sugar called glucose in a person’s blood.
MATERIALS
• ruler
• colored pencils
BACKGROUND
Milk is packed with proteins, fats, and carbohydrates that support the growth, development, and survival of
baby mammals. The main carbohydrate in milk is a sugar called lactose. To digest milk, lactose must be cleaved,
or broken down, by lactase, an enzyme produced in the small intestine. Lactase cleaves lactose into two smaller
sugars, glucose and galactose, which are easily absorbed through the walls of the small intestine. Once these
sugars are absorbed into the bloodstream, they can be delivered to the cells of the body and used for energy.
Figure 1. A diagram showing how the lactase enzyme cleaves the sugar lactose.
As baby mammals grow up and stop drinking their mother’s milk, their bodies usually stop producing the lactase
enzyme (presumably because it is no longer needed). Individuals that do not produce lactase as adults are called
lactase nonpersistent. Most mammals are lactase nonpersistent and do not drink milk as adults. Humans are
unusual in that some adults continue to drink milk from other mammals, such as cows.
When an individual who is lactase nonpersistent drinks milk, they cannot easily break down the lactose in the
milk. The lactose passes from their small intestine to their large intestine, where it is fermented by bacteria.
Fermentation produces various gases in the large intestine, which can cause abdominal pain, bloating,
flatulence, and diarrhea — all symptoms of lactose intolerance, the inability to digest lactose. Most adults are
lactase nonpersistent and thus typically lactose intolerant (although some may not know it because their
symptoms are mild). However, about 35% of the global human population continues to produce lactase into
adulthood. These individuals are called lactase persistent and are typically lactose tolerant, meaning that they
can digest lactose easily and drink milk without problems.
