PrepTest 127, Section 3, Question 20
Newspaper article: People who take vitamin C supplements(47 more words not shown)
Which one of the following,(11 more words not shown)
- AVitamin C taken(19 more words not shown)
- BThe reduction in(23 more words not shown)
- CTaking both vitamin(20 more words not shown)
- DHigh doses of(14 more words not shown)
- ETaking vitamin C(11 more words not shown)
Reading the argument
At first, “people who take vitamin C supplements tend to be healthier” makes me wonder about other differences between those people and everyone else. Perhaps supplement users also exercise more or take other steps to protect their health. But the article's conclusion describes the group's health; it doesn't expressly say vitamin C causes every health advantage.
The evidence that follows creates a clearer problem. The study concerns heart disease. Its final description does specify vitamin C supplements, so we don't have to guess whether these people merely ate more oranges. Still, a lower risk of heart disease is only one part of being healthier overall.
What if these people had another serious health problem? We wouldn't call a treatment good for overall health merely because it improved one measure while harming another. A hypothetical treatment that helped the heart but increased some other disease risk would illustrate the missing comparison.
What we’re looking for
For a weakener, I would look for a health disadvantage that the narrow focus on heart disease leaves out. We can accept the finding about heart disease and still question the broader conclusion.
Working the answers
- A
The study and the conclusion both concern supplements. A difference between vitamin C in a supplement and vitamin C in food doesn't undermine a comparison that stays with supplements throughout. The final sentence resolves that distinction.
- B
Another dietary change could reduce heart-disease risk just as much without undermining the article's claim about supplement users. The argument doesn't say vitamin C is the best or only way to lower that risk. We need evidence against the broader health inference, not a competing way to obtain the same benefit.
- C
Taking C and E together could work better than either alone while people taking C still had the lower heart-disease risk described. The article never claims that C by itself produces the largest possible reduction. A better combination doesn't establish a health disadvantage of taking C.
- DCorrect
Reduced resistance to infectious diseases introduces a potential health cost of the high doses studied. That makes the lower heart-disease risk a less complete basis for declaring these supplement users healthier overall.
The reduction in resistance is only slight, so D doesn't prove that the cost outweighs the heart benefit or that users are less healthy overall. It doesn't need to. It supplies evidence of another health effect that cuts against drawing the broad conclusion from one favorable measure.
- E
A lower cancer risk would add another favorable health finding. That supports the broader picture of health rather than challenging it. An increased cancer risk could have fit our prediction, but this answer gives a decrease.
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