A recent study shows that people living on the continent of North America suffer 9 times more chronic fatigue and 31 times more chronic depression than do people living on the continent of Asia. Interestingly, Asians, on average, eat 20 grams of soy per day, whereas North Americans eat virtually none. It turns out that soy contains phytochemicals called Isoflavones, which have been found to possess disease-preventing properties. Thus, North Americans should consider eating soy on a regular basis as a way of preventing fatigue and depression.
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The argument claims that North Americans should consider eating soy on a regular basis as a way of preventing fatigue and depression. Stated in this way the argument manipulates facts and conveys a distorted view of the situation, using examples of leap of faith and poor reasoning. The conclusion of the argument relies on assumptions for which there is no clear evidence. Hence, the argument is unconvincing and has several flaws.
First, the argument readily assumes that chronic fatigue and chronic depression are a result of only a lack of isoflavones found in soy. This statement is a stretch as there can be many contributing factors, some more important than lack of isoflavones. Thus , the diseases mentioned might not be prevented by consuming soy as other factors might overpower the positive effects produced by soy. The argument could have been much clearer if it explicitly stated lack of isoflavones as one of the contributing factors of chronic fatigue and chronic depression.
Second, the argument readily assumes that soy is the only source of isoflavones . This is again a very weak and unsupported claim as the argument does not explicitly state that other foods consumed by North Americans do not contain the mentioned phytochemicals. Thus the direct relation that the argument establishes between lack of soy consumption and Chronic fatigue and chronic depression comes under serious doubt. If the argument had provided evidence that soy is the only source of isoflavones then the argument would have been a lot more convincing.
Third, the argument draws a conclusion based on a study of only two continents . This casts serious doubt over the conclusion as a study of the remaining continents might not agree with the relationship established between soy consumption and the mentioned diseases. Clearly the argument manipulates the data obtained from the study to favour the conclusion drawn. If the study had been carried out on all continents it would have made the argument more convincing.
Finally, the argument leaves us with unanswered questions. It does not tell us about the subjects of the study and how these subjects were selected. It also does not explicitly answer whether chronic depression and chronic fatigue cause a lack of isoflavones in the body. Without convincing answers to these questions, one is left with the impression that the claim is more of a wishful thinking rather than substantive evidence.
In conclusion, the argument is flawed for the above mention reasons and is therefore unconvincing. It could be considerably strengthened if the author clearly mentioned all the relevant facts. In order to asses of certain situation, it is essential to have full knowledge of all the contributing factors. Without this information, the argument remains unsubstantiated and open to debate.