New Evidence Shows Animal Protein Does Not Shorten Life

Animal protein is not a killer. A new study of nearly 16,000 U.S. adults found no link between eating animal protein and increased risk of death, and even a slight protective effect against cancer-related mortality. Researchers at McMaster University and collaborators analyzed long-term dietary intake using advanced statistical methods, reporting their findings in Applied Physiology, Nutrition, and Metabolism.

Context and Methods

The team drew on data from NHANES III, a national health and nutrition survey conducted between 1988 and 1994, and followed mortality outcomes through 2006. Using the National Cancer Institute method and multivariate Markov Chain Monte Carlo modeling, they estimated long-term intake of animal and plant protein, minimizing the errors that often plague dietary studies.

By linking dietary data with more than 3,800 recorded deaths, the researchers tested whether protein source influenced all-cause, cardiovascular, or cancer mortality. Their approach allowed them to separate usual intake from daily fluctuations, offering a clearer picture of long-term eating habits.

Results and Associations

The analysis revealed no increase in overall or cardiovascular mortality risk from eating animal or plant protein. Importantly, those consuming higher amounts of animal protein had a modest but statistically significant lower risk of cancer-related mortality. Plant protein intake did not show a similar association.

“There’s a lot of confusion around protein – how much to eat, what kind and what it means for long-term health. This study adds clarity, which is important for anyone trying to make informed, evidence-based decisions about what they eat,” said Stuart Phillips of McMaster University (McMaster University).

The researchers also examined circulating levels of IGF-1, a growth factor linked to cancer risk in some studies. They found no associations between IGF-1 and mortality from any cause, further supporting their main conclusion that protein intake itself is not harmful.

Funding and Transparency

The study was funded by the National Cattlemen’s Beef Association (NCBA), a contractor to the Beef Checkoff program, but NCBA was not involved in study design, analysis, or publication. The authors disclosed consulting work for food and nutrition companies, emphasizing that these did not affect the integrity of the findings. As an observational study, the research cannot prove cause and effect but contributes valuable evidence when considered alongside clinical trials.

Key Findings

• Sample size: 15,937 U.S. adults from NHANES III, ages 19 and older
• Study period: Dietary data 1988–1994, mortality follow-up through 2006 (3,843 deaths)
• Methods: NCI method and multivariate Markov Chain Monte Carlo modeling to estimate long-term intake
• Results: No association between animal or plant protein intake and all-cause or cardiovascular mortality
• Cancer risk: Higher animal protein intake linked with modest reduction in cancer-related mortality (HR = 0.95, p=0.04)
• IGF-1: Circulating levels not associated with mortality risk
• Funding: National Cattlemen’s Beef Association (no role in design or analysis)

Takeaway

This large U.S. cohort study found no evidence that eating more animal protein increases mortality risk. Instead, higher animal protein intake was linked to a small reduction in cancer-related deaths, supporting the idea that both animal and plant protein can be part of a healthy diet.

Journal: Applied Physiology, Nutrition, and Metabolism
DOI: 10.1139/apnm-2023-0594