"Salicylates are members of the same chemical family as aspirin, a medicine used to treat headaches. Although many foods are naturally rich in salicylates, for the past several decades, food-processing companies have also been adding salicylates to foods

The argument is about the use of Salicylates as medicine to treat headaches since it shares same chemical family as of Aspirin. This argument is not logically convincing as the argument contains some major flaws.

First, the author assumes that since Salicylates belong to the same chemical family as of Aspirin, it will have the same properties of the Aspirin. It is not possible to assume that both the medicines will have same properties. Perhaps, these medicines may share some similarities in chemical properties or physical structures. However it is not necessary that Salicylates can definitely be used to treat headaches. Moreover, it cannot be assumed that Aspirin alone is used to treat headaches. It is possible that Aspirin is combined with other substances or gone through some chemical processes which is then used to treat headaches.

Second, the author tries to substantiate his argument by providing the report of the twenty-year study as an evidence of fact. The author claims that the study shows that the the average number of headaches reported by participants of the study showed a gradual decline due to the commercial use of salicylates as preservatives. This assumption is dubious as the author did not mention any details of the nature of the study. Did the participants took only foods that were rich in salicylates? Were they under any medications? How severe was their headaches? These are very necessary details to corroborate the argument and the author forgets these details easily. Therefore, the author must have gathered some more logical data about the study in order to corroborate his argument.

Third, the author make an assumption that many foods are naturally rich in salicylates. The author has not provided any proof to show that how the food is naturally rich of this particular chemical substance. Is it found in only a particular kind of food? Or does any component that is usually added to these food.

Finally, the author states that using the Salicylates as flavouring agents is expected to reduce the number of headaches. This conclusion cannot be taken as surety as there are chances that when used an flavour additives, it may cause side-effects. Moreover, this finding doesn't have a proof as it is based on a recent study. Therefore, a research must be done before using it as a flavour agent.

In sum, this argument requires a more deep research in order to study the nature of Salicylates and its use as a medicine to treat headaches.