Folic acid is a nutrient present in leafy vegetables and some other foods. In the blood, folic acid inhibits the...
GMAT Critical Reasoning : (CR) Questions
Folic acid is a nutrient present in leafy vegetables and some other foods. In the blood, folic acid inhibits the formation of substances found in arterial blockages that commonly cause heart attacks. Moreover, in a long-term study of 10,000 individuals, the subgroup with the highest blood levels of folic acid had fewer heart attacks than the subgroup with the lowest levels. Therefore, a decrease in dietary folic acid will increase the risk of a heart attack.
Which of the following, if true, would most strengthen the argument?
Passage Analysis:
| Text from Passage | Analysis |
| Folic acid is a nutrient present in leafy vegetables and some other foods. |
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| In the blood, folic acid inhibits the formation of substances found in arterial blockages that commonly cause heart attacks. |
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| Moreover, in a long-term study of 10,000 individuals, the subgroup with the highest blood levels of folic acid had fewer heart attacks than the subgroup with the lowest levels. |
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| Therefore, a decrease in dietary folic acid will increase the risk of a heart attack. |
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Argument Flow:
The argument starts with basic facts about folic acid, then explains how it works biologically to prevent heart attacks, supports this with study evidence showing the correlation, and finally concludes that reducing folic acid intake will increase heart attack risk.
Main Conclusion:
A decrease in dietary folic acid will increase the risk of a heart attack.
Logical Structure:
The argument uses both biological mechanism (folic acid prevents arterial blockage substances) and correlational evidence (study showing fewer heart attacks in high folic acid groups) to support the causal claim that reducing dietary folic acid increases heart attack risk.
Prethinking:
Question type:
Strengthen - We need to find information that would make us more confident that decreasing dietary folic acid will increase heart attack risk
Precision of Claims
The argument makes specific claims about biological mechanisms (folic acid inhibits harmful substances), study results (high vs low folic acid groups had different heart attack rates), and causation (dietary folic acid decrease causes increased heart attack risk)
Strategy
To strengthen this argument, we need information that eliminates alternative explanations for the study results, confirms the causal chain from dietary intake to blood levels to heart attack prevention, or provides additional evidence supporting the biological mechanism. We should look for options that close logical gaps between correlation and causation.
'Many of the people who had heart attacks during the study were eating a high-fat diet, which is known to contribute to the formation of arterial blockages.' This doesn't strengthen our argument about folic acid. If anything, this introduces an alternative explanation for the heart attacks - maybe it was the high-fat diet, not low folic acid levels, that caused the problems. This could actually weaken the argument by suggesting other factors might be more important than folic acid levels.
'Folic acid cannot be synthesized or stored by the body.' This powerfully strengthens the argument! The key logical gap we need to bridge is: does reducing dietary folic acid actually lead to lower blood levels? If our bodies could make folic acid internally or store it up for future use, then eating less wouldn't necessarily mean having less in our blood. But if we can't synthesize or store it, then we're completely dependent on what we eat. This makes the causal chain rock-solid: less dietary folic acid → lower blood folic acid → more heart attacks.
'Arterial blockages usually take years to develop.' This is interesting background information, but it doesn't really strengthen the connection between dietary folic acid and heart attack risk. The argument already acknowledged this was a long-term study, so we'd expect to see the effects of long-developing blockages. This doesn't add new support to the causal relationship.
'The group that had the fewest heart attacks also had the best exercise habits.' This actually weakens our argument! It suggests that maybe the low heart attack rate in the high-folic-acid group wasn't due to folic acid at all - maybe these people just exercised more. This introduces an alternative explanation that competes with our folic acid theory.
'The subjects in the study were tested for folic acid levels most frequently in the first two years of the study.' This tells us about the study methodology but doesn't strengthen the argument about the relationship between folic acid and heart attacks. It's just procedural information that doesn't impact the causal claims being made.