Blood Glucose Data Analysis Student Handout
Activity
Blood Glucose Data Analysis Student Handout
Assignment #3 - Blood Glucose Levels and Lactose Tolerance
Link to movie (~20 min) to watch to use with this assignment: https:
www.biointeractive.org/classroom-resources/making-fittest-got-lactase-coevolution-genes-and-culture (I recommend reading through the assignment instructions and questions before watching the movie)
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
eaks 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.
BACKGROUND
Milk is packed with proteins, fats, and ca
ohydrates that support the growth, development, and survival of baby mammals. The main ca
ohydrate in milk is a sugar called lactose. To digest milk, lactose must be cleaved, or
oken down, by lactase, an enzyme produced in the small intestine. Lactase cleaves lactose into two smaller sugars, glucose and galactose, which are easily abso
ed through the walls of the small intestine. Once these sugars are abso
ed 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
eak 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 dia
hea — 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.
Part 1.
There are several ways to test whether someone is lactase persistent or nonpersistent. One method, the blood glucose test, is shown in the short film Got Lactase? The Co-evolution of Genes and Culture. Table 1 shows the blood glucose levels of the film’s na
ator, Spencer Wells (person A), and six other individuals over time. The glucose levels were measured using glucose strips and a glucose reader similar to the one in the film. After baseline levels (i.e., the ones at “0 minutes”) were measured, each person drank a liter of milk. Their blood glucose levels were measured again at 15, 30, 45, and 60 minutes after drinking the milk.
Table 1. Blood glucose test results for seven adults tested in Sarah Tishkoff’s laboratory.
Blood Glucose (mg/dL)
Individual
0 minutes
15 minutes
30 minutes
45 minutes
60 minutes
Person A
117
128
146
160
152
Person B
97
111
135
154
143
Person C
96
99
99
100
98
Person D
95
97
99
101
102
Person E
108
128
132
141
139
Person F
94
109
128
143
140
Person G
97
96
96
87
86
1. Plot the data in Table 1 using Google sheets, Excel or any graphing program available. The example below is a model and just includes the results for Person A. You can plot what ever intervals you like for time, it does not have to match the model below. Make sure axes are labeled with units.
80
90
100
110
120
130
140
150
160
0
10
20
30
40
50
60
Blood Glucose (mg/dL)
Time (minutes)
Person A
Title for Graph: In your graph you will include a descriptive title for the graph.
After graphing the data, answer the following questions.
2. Explain why blood glucose after consumption of milk can indicate someone’s ability to digest lactose.
3. Divide the individuals in Table 1 into two groups (1 and 2) based on their blood glucose test results. Write the individuals in each group below.
4. Based on these data, do you think the individuals in Group 1 are lactase persistent or nonpersistent? What about the individuals in Group 2? Explain.
5. If the blood glucose test was performed on people from the Maasai population in Kenya, would their results be more like those of the individuals in Group 1 or Group 2? Explain your prediction.
6. A person taking a blood glucose test is usually told to fast (i.e., to not eat or drink anything but water) before the test. Why do you think that might be necessary?
Part 2: Another common way to test whether a person is lactase persistent or nonpersistent is the hydrogen
eath test. This test uses the amount of hydrogen in a person’s
eath to check for lactose fermentation. As described in the “Background” section, undigested lactose is fermented by bacteria in the large intestine. Fermentation produces several gases, including hydrogen, that can exit the body through the anus. These gases can also be abso
ed into the blood, circulated to the lungs, and eliminated through the
eath.
Figure 2. A diagram comparing what happens to lactose in the intestines of individuals with and without the lactase enzyme.
Table 2 shows the levels of hydrogen in the
eath of four adults tested for lactase persistence. As in Table 1, the measurements at “0 minutes” represent baseline levels before drinking milk. The other measurements were taken at various times after drinking milk.
Table 2. Hydrogen test results for four adults.
Hydrogen Breath Levels (ppm)
Individual
0 minutes
30 minutes
60 minutes
90 minutes
120 minutes
Aye
5
6
9
8
5
Bee
4
9
16
33
34
Cee
6
8
11
29
32
Dee
4
6
6
7
6
7. Create your own graph of the data in Table 2. Your graph should include a title, labels for the x- and y-axes, and a legend.
8. Which individuals in Table 2 are likely to be lactase persistent? Which are likely to be lactase nonpersistent ? Explain, referencing the table and your graph.
Enzymes & Reactions Updated January 2020 www.BioInteractive.org Page 2 of 5