Many calcium supplements contain lead, a potentially dangerous substance even in small amounts. The body can safely store in bones trace amounts of lead from food, but high levels of lead in the blood are a major public health concern, associated with anemia and nerve damage. Despite this, many doctors contend that for some people calcium supplements containing lead are preferable to no calcium supplements at all.

"Surprising" Phenomenon
Why do doctors argue that, for some people, calcium supplements with lead are better than no calcium supplements, even though even small amounts of lead can be harmful?

Objective
The correct answer will be a hypothesis that explains a key difference between taking calcium supplements with lead and not taking calcium at all. That difference must show that, for some people, not taking calcium at all has even worse consequences than taking calcium supplements that may contain lead.

A
Some fruits and vegetables contain trace amounts of lead derived from the soil in which they are grown.
This doesn’t explain why not taking calcium at all might have even worse consequences than taking calcium supplements that may contain lead. Also, the stimulus tells us that the body can safely store trace amounts of lead from food anyway.
B
It is difficult to ensure that one has completely eliminated trace amounts of lead from one’s diet.
Again, this does not provide an explanation that might resolve the discrepancy. We need a reason why doctors support taking calcium supplements with lead rather than not taking calcium at all. We aren’t concerned with whether someone can completely eliminate lead from their diet.
C
Lead is only one of the common public health concerns that are associated with anemia and nerve damage.
There may be many other public health concerns that cause anemia and nerve damage, but we are only concerned with lead. We still need an explanation for why not taking calcium is worse for some people than taking calcium that contains lead.
D
A high-calcium diet decreases the amount of lead that the body is able to tolerate safely.
This increases the discrepancy by suggesting that calcium might actually reduce people’s ability to tolerate lead. We need a reason why calcium supplements are so essential for some people that it’s better to take ones with lead than to not take them at all.
E
When calcium intake is insufficient, the body draws calcium from bones, releasing stored lead into the bloodstream.
This explains why, for some people, not taking calcium at all is worse than taking calcium supplements with lead. Without enough calcium, the body pulls calcium from the bones, releasing stored lead into the bloodstream, which can lead to anemia and nerve damage.

1 comment

Critic: In her presentation of important works of art in her art history textbook, Waverly claims to have presented only objective accounts: “I have sought neither to advocate nor to denigrate what I included.” In writing about art, a pretense of objectivity never succeeds: clearly, Waverly writes much better about art she likes than about art to which she is indifferent.

Summary

Waverly claims to be objective when writing about important works of art in her art history textbook. However, objectivity never succeeds when writing about art. Therefore, Waverly writes much better about art she likes than about art she’s indifferent about.

Strongly Supported Conclusions

Waverly does not actually write about art in an objective way she intended.

A
Waverly believes that a historian of art should not prefer certain works of art to other works of art.

This answer is unsupported. We don’t know what Waverly believes. We only know her intention to write objectively.

B
Waverly has only included works of art that she has strong opinions about in her textbook.

This answer is unsupported. We don’t know whether Waverly has strong opinions about any of the artworks in her textbook.

C
Waverly wrote her textbook with the intention of advocating the works of art that she likes best.

This answer is unsupported. We only know that Waverly’s intention was to be objective in her writing. We don’t know about any of her other intentions.

D
Waverly has not succeeded in her intended objectivity about works of art discussed in her textbook.

This answer is strongly supported. If Waverly wrote about some artworks better than others based on her personal feelings, then she is not writing objectively.

E
Waverly does not really believe that objectivity is a desirable trait in an art history textbook.

This answer is unsupported. We don’t know what Waverly believes. We only know her intention to write objectively.


6 comments

While grapefruit juice is a healthy drink, it has been discovered that a chemical in the juice affects how certain medicines are absorbed, with the result that normal medicinal doses act like higher doses. Getting the wrong dose is dangerous. Since it is always desirable to take the lowest effective dose, the best medical approach would be to take lower doses of these medicines along with prescribed amounts of grapefruit juice.

Summarize Argument
The author concludes that lower dosages of certain medicines should be taken with grapefruit juice. This is because it’s best to take low dosages of medicine when possible, and grapefruit juice intensifies dosages. Thus, a lower dosage taken with grapefruit juice would act like a normal dosage.

Notable Assumptions
For this to be the “best medical approach,” the author must believe that grapefruit juice is consistent in its chemical composition. If one glass were to have even slightly more of the chemical than another glass, then the approach would be seriously, dangerously flawed.

A
The amount of the chemical in grapefruit juice is highly unpredictable from glass to glass.
Each glass of grapefruit juice isn’t equal. If the concentration of the chemical was significantly higher in one glass, then the medicine would be elevated to a dangerous dosage. This wouldn’t be “the best medical approach” by any standard.
B
Grapefruit juice is less expensive than most of the medicines with which it interacts.
We don’t care about how much grapefruit juice costs.
C
When scientists removed the chemical from grapefruit juice, the juice no longer affected how certain medicines were absorbed.
The author knows this. It’s integral to their argument about how grapefruit juice should be used with low dosages of medicine.
D
The chemical in grapefruit juice works by inhibiting an enzyme in the body that affects how certain medicines are metabolized.
This explains how grapefruit juice interacts with medicines. The author’s argument relies on this mechanism working.
E
Long before the chemical in grapefruit juice was identified, doctors were advising patients who took certain medicines to avoid grapefruit juice.
We don’t care that doctors probably knew that grapefruit juice intensifies medicines. We’re trying to weaken the author’s recommendation.

14 comments