Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good info supported by references that need to be updated

I agree with the reviewer who said: 'It cites heavily dated secondary sources (nutrition books, encyclopedias, and journal articles), such as John McDougall's "The McDougall Program" (1990), Neal Barnard's "Food for Life" (1993), and articles in journals from the 1970s and 80s).' It's good to have the sources cited, but that makes this book more like second-hand reporting. Worse, the sources all all of the standard ones for vegan diet advocates, and they're all outdated by way more than a decade. Updating it might make an even better case, because we've learned more since and more of the info is now supported and accepted in the mainstream.