Journalist: Support People whose diets contain a relatively large amount of iron are significantly more likely to develop Parkinson's disease than are those whose diets contain less of this mineral. Conclusion Limiting one's intake of meats, seafood, and other foods rich in iron should thus reduce one's chances of contracting this disease.
The journalist concludes that limiting the intake of iron-rich foods should reduce one’s chances of develop Parkinson’s disease. This is based on an observed correlation: that people with high dietary iron intake are more likely to develop Parkinson’s than people with low iron intake. For the author, this leads to the implied hypothesis that iron intake contributes to Parkinson’s.
The journalist assumes that iron intake causes Parkinson’s, rather than both higher iron intake and higher likelihood of contracting Parkinson’s disease having a shared cause.
Which one of the following, if true, most strengthens the journalist's reasoning?
Most people who have a genetic predisposition to Parkinson's disease have no more iron in their diets than people without the predisposition.
This strengthens by ruling out one alternate explanation for the correlation between high iron intake and Parkinson’s disease, i.e. that people genetically predisposed to Parkinson’s disease happen to also consume more iron.
Weaken: Introduce or suggest an alternate explanation for the target phenomenon.
Strengthen: Helps to eliminate an alternate explanation for the target phenomenon.
Many of the vegetables regularly consumed by vegetarians who do not contract Parkinson's disease are as rich in iron as meat and seafood.
This is irrelevant, since the author does not compare iron contents in different types of food. Meat and seafood are just possible examples of iron-rich foods.
Children and adolescents require a much larger amount of iron in their diets than do mature adults.
This is irrelevant, because the author does not make any claims about age, or even about the amount of iron required in peoples’ diets. The author just compares iron intake for people who do and don’t develop Parkinson’s, and this doesn’t affect that correlation.
The iron in some foods is much less easily absorbed by the body than the iron contained in other foods.
How easily iron is absorbed from different food sources is irrelevant to the author’s hypothesis that iron intake causes Parkinson’s, and that a general reduction of iron intake from food should thus lower the risk of Parkinson’s disease.
The amounts of iron-rich foods consumed by people starts to decline beginning at age 50.
The author doesn’t make any claims about the ages at which people tend to consume iron, so this is irrelevant. The correlation between iron intake and Parkinson’s isn’t affected by age-based trends in iron intake.
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