PrepTest 146, Section 3, Question 21
Journalist: People whose diets contain a relatively large(42 more words not shown)
Which one of the following,(7 more words not shown)
- AMost people who(19 more words not shown)
- BMany of the(20 more words not shown)
- CChildren and adolescents(14 more words not shown)
- DThe iron in(17 more words not shown)
- EThe amounts of(12 more words not shown)
Reading the argument
Does the extra iron cause the disease, or are these people different in another way? A diet high in iron and a greater chance of Parkinson's disease occur together. That alone doesn't show that changing the diet changes the risk.
For example, suppose a genetic predisposition makes people both more likely to develop Parkinson's and more inclined to eat iron-rich foods. Then the two things could occur together even if the iron isn't causing the disease. Or some feature of the communities where people eat those diets could explain the pattern.
What we’re looking for
We need to strengthen the journalist's recommendation to reduce iron intake. I'd like a mechanism: perhaps extra dietary iron causes some bodily change that raises the risk. That's a hypothetical way to support the argument, not a claim about how Parkinson's actually develops. Let's see what connection the answers give us.
Working the answers
- ACorrect
This doesn't give us the mechanism I wanted, and at first it might seem to be saying that diet and risk have little to do with each other. But notice which comparison it makes. People with the genetic predisposition generally aren't eating more iron than people without it.
That pushes back against our alternative explanation: perhaps the predisposition itself makes people eat more iron, producing the observed association. A makes that story less convincing. It doesn't eliminate every alternative or prove that iron causes Parkinson's. It supplies modest support by weakening one explanation that would undermine the journalist's reasoning.
- B
Vegetables can contain as much iron as meat or seafood. That doesn't show that reducing iron lowers the risk of Parkinson's. These vegetarians eat some iron-rich foods without developing the disease, but we aren't given the overall amounts they consume or a useful comparison of disease rates across diets. Listing another source of iron doesn't establish the causal connection.
- C
Nutritional requirements are a different issue. Children could need more iron than adults whether or not iron affects the risk of Parkinson's. C might matter when considering someone's overall dietary needs, but it doesn't support the causal claim behind this recommendation.
- D
Different foods could deliver different amounts of usable iron to the body. We still need a connection between that iron and the disease. D doesn't tell us which people absorb more, how absorption relates to their risk, or why reducing iron-rich foods would reduce that risk.
- E
A decline in iron consumption after age 50 doesn't tell us what happens to disease risk as a result. Without that connection, the age-related dietary trend doesn't support the journalist's recommendation.
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