LSAT Explanation PT 40, S1, Q17: Researcher: Hard water contains more calcium

LSAT Question Stem

Which one of the following, if true, most undermines the researcher's argument? 

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is E. 

LSAT Question Complete Explanation

First, let's analyze the argument in the passage. The researcher claims that since hard water contains more calcium and magnesium than soft water, those who drink mostly soft water have an increased risk of heart disease, stroke, and hypertension. The basis for this claim is that people being treated for these conditions tend to have lower levels of magnesium in their blood. The structure of the argument is as follows:

Premise: Hard water contains more calcium and magnesium than soft water.

Premise: People being treated for heart disease, stroke, and hypertension tend to have lower levels of magnesium in their blood.

Conclusion: Drinking mostly soft water increases the risk of heart disease, stroke, and hypertension.

An "Evaluate" question for this argument could be: "Does the lower level of magnesium in the blood of people with heart disease, stroke, and hypertension actually cause these conditions, or is it just a correlation?"

Now, let's discuss the answer choices for the Weaken question, which asks us to find the option that most undermines the researcher's argument.

a) Magnesium deficiency is not uncommon, even in relatively prosperous countries with an otherwise generally adequate diet. - This answer choice does not directly address the relationship between magnesium levels and heart disease, stroke, and hypertension. It only provides information about the prevalence of magnesium deficiency. Therefore, it does not weaken the argument.

b) Magnesium is needed to prevent sodium from increasing blood pressure. - This answer choice actually strengthens the argument by providing a reason why low magnesium levels could contribute to heart disease and high blood pressure. Thus, it is not the correct answer.

c) As people age, their ability to metabolize magnesium deteriorates. - This answer choice suggests another reason for disrupted magnesium intake, but it does not directly weaken the relationship between magnesium levels and heart disease, stroke, and hypertension. Therefore, it is not the correct answer.

d) The ingestion of magnesium supplements inhibits the effectiveness of many medicines used to treat high blood pressure and heart disease. - This answer choice does not weaken the argument because it does not address the relationship between low magnesium levels and the development of heart disease, stroke, and hypertension. It only discusses the interaction between magnesium supplements and certain medications. Thus, it is not the correct answer.

e) Compounds commonly used to treat hypertension and heart disease diminish the body's capacity to absorb and retain magnesium. - This is the correct answer choice. It undermines the researcher's argument by suggesting that the low magnesium levels observed in people with heart disease, stroke, and hypertension could be a result of the treatment for these conditions rather than the cause. This breaks the assumed cause-and-effect relationship between low magnesium levels and the development of heart disease, stroke, and hypertension.