Animal products—especially red and processed meat—are a major driver of chronic disease in the Standard American Diet. Heart disease, type 2 diabetes, many cancers, and inflammatory conditions track closely with how much meat people eat.
Meat delivers cholesterol and saturated fat that promote atherosclerosis. It also raises IGF-1 (a growth hormone linked to cancer promotion), heme iron (associated with colorectal cancer risk), and inflammatory compounds formed when flesh is cooked at high heat (HCAs and PAHs). Processed meats such as bacon, sausage, deli meat, and hot dogs are classified by the World Health Organization as carcinogenic to humans.
Large population studies and clinical programs (including work popularized by physicians such as John McDougall, MD, Caldwell Esselstyn, MD, and Neal Barnard, MD) show that removing animal products and centering meals on starches, vegetables, fruit, and legumes improves cholesterol, blood pressure, blood sugar, and body weight—often within weeks.
Meat is also unnecessary for protein. All whole plant foods contain protein, and eating enough calories from plants easily covers human requirements without the baggage of animal fat and cholesterol. For anatomy and physiology comparing humans to carnivores, see Humans vs Meat Eaters.
Video: the basics
For more science summaries, visit NutritionFacts.org and Dr. McDougall, and explore related pages on dairy, eggs, and fish.