Self-study
A 24-year study of 1,500 adults showed that those subjects with a high intake of foods rich in beta-carotene were much less likely to die from cancer or heart disease than were those with a low intake of such foods. ██ ███ █████ █████ ██████ █████████████ ███████████ ███ ██ █████ ███ ██ ████████ ██ ████████ ██████ ██ ███ ██████ ██ ████████ ██ █ ████████ █████ ██ ██████ ███████
"Surprising" Phenomenon
Why did people who ate lots of beta-carotene in their food avoid deadly cancer and heart disease when people taking beta-carotene supplements experienced no changes to their health?
Objective
The correct answer must fail to explain why people in the two studies experienced such different health outcomes. Every wrong answer, meanwhile, will state a flaw in the studies’ designs or explain why people who eat foods rich in beta-carotene are less likely to die from cancer and heart disease than those who take a supplement.
17.
Each of the following, if █████ █████ ████ ██ ███████ ███ ████████ ███████████ ███████ ███ ███████ ██ ███ ███ ███████ ███████
a
The human body █████████ ███ █████████████ ███████ ██ █████ ████ ████ ███████████ ████ ██ ████ █████████████ ████████████
This would explain the discrepancy. People who eat foods rich in beta-carotene process more of it than those who only take supplements.
b
Beta-carotene must be █████ ███ ██████ ████ ██ █████ ██ ████ ███ █████████████████ ████████
This would explain why people in the first study showed benefits while people in the second study did not. Those in the second study did not consume high levels of beta-carotene over a long enough period to achieve health benefits.
c
Foods rich in █████████████ ████ ████ ██ ███████ █████ █████████ ████ ██████ ██ ███ █████ ██████ ██████████ ██ ██████████████
This would explain the discrepancy. People who eat foods rich in beta-carotene eat food also rich in other nutrients, and those nutrients cause the lower risk of deadly cancer and heart disease.
d
In the 12-year ██████ ████ ██ ███ ████████ ████ █████ █████████████ ███████████ ███ ████ ████ █████ █ ████████
This does not explain the discrepancy. The author states that people who took the supplements experienced no health benefits, regardless of the placebo group.
e
In the 24-year ██████ ███ ██████████ ██ ███ ████████ ███ ███ █ ████ ██████ ██ ██████████████████ █████ ███ ██████ ██████████ ███ ████ ███████ ████ ███ ██████████ ██ ███ ████████ ████ █ ███ ██████ ██ ██████████████████ █████ ███ ███████
This would explain the discrepancy. People in the first study were less likely to die of cancer and heart disease because they were less likely to smoke cigarettes.