What you eat and how long you live

How Not to Die, published in 2015 by physician Michael Greger with Gene Stone, is organised around a provocative premise: that the major chronic diseases responsible for most deaths in the Western world are largely preventable through diet, and that the evidence for this has been available for decades. Greger works through fifteen of the leading causes of death — from heart disease to Parkinson's — and in each case reviews the dietary research.

The core argument is that whole plant foods — vegetables, fruits, legumes, whole grains, nuts and seeds — have consistent associations with reduced disease risk across a wide range of conditions. Greger points to populations that eat in this way and show markedly lower rates of the diseases that dominate Western mortality statistics. He argues that processed foods, refined carbohydrates and, more controversially, animal products are associated with elevated risks for several conditions.

The second half of the book introduces Greger's 'Daily Dozen' — a checklist of food groups he recommends eating every day, from leafy greens and berries to flaxseeds and legumes. The approach is practical and specific, which gives the book its usefulness beyond the theoretical argument. Greger runs the non-profit NutritionFacts.org, where he reviews newly published nutrition research.

A necessary caveat: nutrition research is methodologically difficult. Most studies rely on self-reported dietary recall, which is unreliable; observational data cannot always be disentangled from confounding lifestyle factors. Greger's conclusions are more confident than the evidence base strictly warrants in some areas, particularly regarding animal products. The book is best read as a strong argument for eating more whole plant foods, rather than a settled scientific verdict on all dietary questions.