Researchers Explore the Complicated Legacy of Red Meat

Fast forward to the 21st century, and that same food source has become a double-edged sword. High consumption of red and processed meat is now linked to chronic diseases including cancer, heart disease, obesity and type 2 diabetes. At the same time, the industrial systems required to meet modern demand for red meat carry significant environmental consequences, contributing to deforestation, greenhouse gas emissions, biodiversity loss and water scarcity.  Together, these health and environmental pressures have reshaped red meat from an evolutionary advantage into a modern public health and sustainability concern.

“Meat is a huge deal, especially in the United States,” said Pascal Gagneux, PhD, contributing author of the review, professor of pathology and anthropology and executive co-director of the Center for Academic Research and Training in Anthropogeny (CARTA) at UC San Diego. “The U.S. makes up less than 5% of the world population yet consumes more than 20% of globally produced beef. The challenge is that it’s not simply a black-and-white issue, although the picture is becoming darker when it comes to processed red meat.”

Bridging ancient biology and modern disease, researchers are also investigating how Neu5Gc, a sugar found in red meat but not naturally produced by humans, can become incorporated into human cells and be recognized as “foreign” by the immune system, triggering low-grade immune reactions. In humans, this may translate into chronic inflammation, a persistent immune response that can gradually damage tissues over time. In engineered models, red meat sugars have been shown to provoke immune responses that may promote tumor growth, highlighting the complex relationship between diet, inflammation, immunity and cancer.

“In 2015, the World Health Organization classified processed meat as a Group 1 carcinogen, meaning there’s strong evidence it can cause cancer in humans. Red meat was classified as Group 2A — probably carcinogenic — based on more limited evidence,” said Juston Jaco, contributing author of the research review and PhD candidate in the Biomedical Sciences Graduate Program. “That leaves us holding two truths at once: meat likely played an important role in human evolution and nutrition, yet high consumption, especially of processed meat, may also contribute to disease in modern diets.”

Jaco added that researchers are increasingly looking at not just how much meat we eat, but what it replaces in the human diet. For most people, meat is likely replacing fiber-rich plant foods that support the gut microbiome and overall health. The broader message isn’t necessarily to never eat meat, but rather what the author Michael Pollan famously summarized, “Eat food. Not too much. Mostly plants.”

From prehistoric hunting grounds to modern grocery store aisles, red meat has traveled a long evolutionary and cultural path. Once a survival-essential staple, it now sits at the center of intersecting debates about human health, chronic disease and environmental sustainability. The research suggests that red meat’s legacy is neither purely beneficial nor purely harmful, but deeply context dependent.

Ajit Varki, MD, distinguished professor of medicine and cellular and molecular medicine, and founding co-director of CARTA, who originated the concept of this transdisciplinary review, noted that "the unfortunate polarization of red meat reflects a deeply human tendency toward tribalism, as well as our capacity to deny, ignore or distort reality by embracing extreme positions on issues like red meat production and consumption."

The authors conclude that reducing consumption of processed red meat, alongside investing in lower-impact production systems and plant-based alternatives, may offer a path toward aligning dietary traditions with modern health and environmental realities.