LSAT 147 – Section 1 – Question 21

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PT147 S1 Q21
+LR
Weaken +Weak
Causal Reasoning +CausR
A
15%
156
B
3%
154
C
7%
157
D
8%
159
E
67%
164
148
156
163
+Harder 147.09 +SubsectionMedium

People with higher-than-average blood levels of a normal dietary by-product called homocysteine are twice as likely to be diagnosed with Alzheimer’s disease as are those with average or below-average homocysteine levels. Thus, it is likely that the risk of developing Alzheimer’s disease could be reduced by including in one’s diet large amounts of B vitamins and folic acid, which convert homocysteine into substances known to have no relation to Alzheimer’s disease.

Summarize Argument: Phenomenon-Hypothesis
The author concludes that Alzheimer’s risk can be reduced by converting homocysteine into other substances. This is based on the fact that people with above-average levels of homocysteine have higher risk of being diagnosed with Alzheimer’s.

Notable Assumptions
The author assumes that there’s no other explanation for the correlation between above-average homocysteine levels and increased risk of Alzheimer’s.

A
Many Alzheimer’s patients have normal homocysteine levels.
A correlation between above-average homocysteine and Alzheimer’s allows for outliers. There can be Alzheimer’s patients with normal or even below-average homocysteine levels.
B
The substances into which homocysteine is converted can sometimes have harmful effects unrelated to Alzheimer’s disease.
If the effects are unrelated to Alzheimer’s, then they have no impact on the conclusion, which is focused only on whether Alzheimer’s can be reduced by converting homocysteine to those substances.
C
B vitamins and folic acid are not metabolized by the body very efficiently when taken in the form of vitamin-mineral supplements.
This just suggests B vitamins and folic acid should be taken in other forms besides vitamin-mineral supplements. The author never suggested any specific form in which we take B vitamins and folic acid.
D
People whose relatives contracted Alzheimer’s disease are much more likely to develop Alzheimer’s than those whose relatives did not.
This suggests that there’s also a genetic component to Alzheimer’s. But there could be a genetic component to having higher homocysteine levels. In addition, it’s possible for there to be multiple, independent causes of Alzheimer’s.
E
Alzheimer’s disease tends to increase the levels of homocysteine in the blood.
This provides an alternate explanation for the correlation observed. If Alzheimer’s increases homocysteine, we’d expect people with Alzheimer’s to have higher levels of homocysteine, even if homocysteine doesn’t cause Alzheimer’s.

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