Dr. Catherine Shanahan opens Deep Nutrition with her foundational premise: traditional food preparation methods and dietary patterns across numerous historical cultures encode genuine nutritional wisdom that modern industrial food processing and mainstream nutritional science have significantly overlooked, with this oversight contributing meaningfully to modern chronic disease patterns.

Shanahan's foundational argument:

• She draws on her medical practice and research examining traditional dietary patterns across genuinely diverse cultures, arguing these traditional patterns, despite significant surface-level variation, share underlying nutritional principles that modern industrial food processing has significantly disrupted or eliminated
• Shanahan argues that modern nutritional science's tendency toward isolating and studying individual nutrients, rather than examining whole traditional dietary patterns and preparation methods, has caused significant, health-relevant traditional food wisdom to be overlooked or dismissed
• This foundational premise sets up the book's overall project: examining specific traditional food categories and preparation methods Shanahan argues are nutritionally significant, while presenting genetic and epigenetic mechanisms she argues explain traditional dietary patterns' health significance

This foundational framing establishes Shanahan's overall approach: combining traditional dietary pattern examination with genetic and epigenetic mechanistic explanation, distinguishing her approach from both purely traditional-wisdom-based dietary advice and purely conventional nutritional science.