PrepTest 151, Section 3, Question 20
The level of triglycerides in the blood rises(56 more words not shown)
Which one of the following,(6 more words not shown)
- APeople with a(25 more words not shown)
- BTriglyceride levels above(16 more words not shown)
- CShortly after a(15 more words not shown)
- DHeart disease interferes(7 more words not shown)
- EPeople who maintain(17 more words not shown)
Reading the argument
If the body doesn't process triglycerides adequately, their level rises. That part makes sense: something that isn't being cleared can build up.
Then we get a threshold. Patients above 1 milligram per milliliter are twice as prone to heart attacks. I'd initially wonder what gets someone past that level. Knowing that something raises a level doesn't, by itself, tell us how far it raises it.
The author moves on to a causal conclusion: consuming large amounts of fat, processed sugar, or alcohol probably contributes to heart disease because those substances raise triglyceride levels. But the research has only connected a high level with heart attacks. Why does that association show which way the explanation runs?
What we’re looking for
One possible thought is that diet causes both high triglycerides and heart problems. That would question the proposed role of triglycerides, but it wouldn't refute this argument's actual claim about consumption contributing to disease. For a weakener, we need to be more careful: look for a reason that the observed association doesn't support that causal route.
Working the answers
- A
Diet and activity both change in this comparison. Vigorous exercise could offset a harmful effect of a high-fat diet, leaving active high-fat eaters better off than sedentary low-fat eaters. That wouldn't show the diet contributes no risk. A doesn't isolate the proposed dietary effect or directly explain the triglyceride association another way.
- B
Other serious illnesses don't settle whether the same factor contributes to heart disease. A higher triglyceride level could be related to several health problems. The existence of those other risks doesn't undermine the particular connection the author claims.
- C
This supports the link from consuming alcohol and sugar to triglyceride levels: stop consuming them and the level falls. But it says nothing about what then happens to heart-disease risk. That is the connection we need to question. A decline in the level alone doesn't resolve whether the level is a cause, an effect, or a marker of disease.
- DCorrect
Heart disease itself can interfere with metabolism, and the first sentence tells us inadequate metabolism raises triglyceride levels. Now we have a route from heart disease to high triglycerides. That can explain why high levels and heart problems occur together without using the author's proposed route from consumption through triglycerides to disease.
D doesn't prove that triglycerides can never contribute to disease too. It gives us a competing explanation of the association, which weakens the author's use of that association as evidence for the claimed cause.
- E
This tells us what people following strict health routines tend to consume. It doesn't compare their heart-disease outcomes or explain why triglyceride levels and heart attacks occur together. A pattern of health-conscious behavior isn't, by itself, evidence about which factor causes this disease.
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