In order to determine the intended audience for any article or text, you must utilize two skills: identifying context clues and making inferences.
The first context clue to consider is the publication itself: CSI, which stands for Committee for Skeptical Inquiry. According to the website's "about" page, this committee considers itself a scientific and educational organization whose goal is to bring together those interested in "paranormal" or "fringe science," examine and research these fields, and educate others through publications and conferences. It could be inferred, therefore, that the intended audience of any article published by this committee would include either scientists or educators (and likely both) who are interested in pushing the boundaries of traditional scientific subjects and inquiries into more unknown realms.
When you read and obtain context clues from the actual article, you could further consider that the audience would likely include scientists, educators, and others who are interested in the science of nutrition. It is certainly possible that this author hoped to reach not only his peers, but those in the medical field (health/nutrition), government (the FDA, perhaps), and finally, those who have published similar articles in science and nutrition who have relied on what the author criticizes as "pseudoscience" for the bulk of their scientific claims. The tone of the article seems to suggest he's not only seeking support and agreement for his side of the argument, but also wishes to ruffle the feathers (so to speak) of those who practice research and publication in the nutrition field and utilize methods this author considers to be erroneous.