The search for optimal dietary advice is a significant challenge for science and public health. Current national guidelines are frequently updated but often rely on contested evidence. Nutritional choices are crucial, yet many people seek information from unreliable sources like family, friends, news articles, and television, rather than healthcare professionals or registered dietitians. Misinformation can easily spread and become entrenched. This study investigated the credentials of authors of best-selling nutritional books and analyzed the range of nutritional advice and health claims made in their summaries to gauge the extent of conflicting information available to the public.

The introduction mentions the challenge of establishing definitive nutritional advice and the reliance on frequently updated, yet contested, evidence in national guidelines. It also highlights the prevalence of seeking dietary information from informal and potentially unreliable sources. While the paper does not include a formal literature review section, the introduction implicitly references existing literature on the challenges of nutritional research and public perception of nutrition.

The researchers identified the top 100 best-selling nutrition-focused books from 2008-2015 using sales data. Summaries were extracted from Google Books and analyzed for claims regarding weight loss, disease prevention/cure, energy levels, and lifespan. Key nutritional recommendations were also extracted and categorized. Author credentials (highest degree and occupation) were researched using online searches, university directories, and Google Scholar. A text-mining analysis was performed on seven of the top ten best-selling books to identify the frequency of terms like "systematic review," "meta-analysis," and "randomized controlled trial."

The study found that 80 of the 100 books mentioned weight loss, with a median recommended program length of 21 days and a median weight loss goal of 15.5 pounds. Thirty-one books claimed to prevent or cure diseases, including diabetes, heart disease, cancer, and dementia. Nutritional recommendations were highly inconsistent and contradictory across books, regarding carbohydrates, dairy, protein, and fat consumption. Of the 83 unique authors, 33.7% had an M.D. and 6% had a Ph.D., with many having occupations unrelated to nutrition. Of 20 authors claiming university affiliation, only seven had verifiable current appointments. Text mining revealed limited use of evidence-based terminology in the analyzed books. Several authors had faced criticism, legal action, or professional repercussions related to their claims.

The study demonstrates a significant discrepancy between the prevalence of misleading claims in popular nutritional books and the lack of scientific evidence to support them. The heterogeneity of advice, combined with frequently unsubstantiated claims and the questionable credentials of many authors, raises serious concerns about the potential harm of this information on public health. The findings underscore the need for improved regulatory frameworks and enhanced public awareness of the limitations of many popular nutritional books. The influence of these books on public opinion may surpass that of peer-reviewed scientific literature.

The study highlights the widespread dissemination of conflicting and often unsubstantiated nutritional advice through best-selling books. The lack of consistent evidence-based practice and the varied author credentials raise serious concerns about public health. Increased public awareness and potential regulatory interventions are needed to improve the quality of nutritional information available to the public. Further research should explore the influence of social media and other emerging sources of nutritional advice.

The study analyzed book summaries from Google Books, which may not fully reflect the content of the entire books. The analysis focused on primary authors only, and other experts referenced within the books were not evaluated. Future research could use qualitative methods to assess full texts and analyze emerging sources of nutritional information online.