Landmark Research Challenges Long-Held Assumptions on Animal Protein and Health Outcomes

September 6, 2025

Ontario, Canada - In a groundbreaking analysis that could reshape dietary recommendations, researchers from McMaster University have found that consuming animal-sourced proteins—such as meat, eggs, and dairy—is not associated with an increased risk of premature death. More surprisingly, higher intake of these proteins appears to offer a modest protective effect against cancer-related mortality, according to the study involving nearly 16,000 American adults.

The findings, detailed in the journal *Applied Physiology, Nutrition, and Metabolism*, challenge decades of research linking red and processed meat consumption to higher risks of cancer, heart disease, and overall mortality. Instead, the study suggests that animal proteins may play a beneficial role in a balanced diet, potentially due to their nutrient density, including essential amino acids, vitamins, and minerals that support overall health.

Lead researcher Yanni Papanikolaou, MPH, president of Nutritional Strategies Incorporated, emphasized the implications for public health. "When both observational data like this and clinical research are considered, it’s clear both animal and plant protein foods promote health and longevity," Papanikolaou stated in a university press release. The research was supervised by Stuart M. Phillips, professor and chair of the Department of Kinesiology at McMaster University, who highlighted the confusion surrounding protein sources. "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."

The study drew from the National Health and Nutrition Examination Survey (NHANES III), a comprehensive U.S. dataset collected between 1988 and 1994. Researchers analyzed dietary habits of 15,999 adults aged 19 and older, tracking their protein intake from both animal and plant sources. They then followed participants for an average of 12 years to assess mortality outcomes from all causes, cardiovascular disease, and cancer.

Key results showed no significant associations between total protein intake—whether from animal or plant sources—and the risk of death from any cause or cardiovascular disease. However, when animal and plant proteins were examined separately, a notable pattern emerged: individuals with higher animal protein consumption experienced a modest but statistically significant reduction in cancer-related mortality. Specifically, the data indicated a small protective effect, with no elevated risks observed across age groups, including younger adults under 65, middle-aged individuals (50-65), and those over 65.

To ensure accuracy, the team employed rigorous statistical methods, including the National Cancer Institute's (NCI) method for estimating usual dietary intake and multivariate Markov Chain Monte Carlo (MCMC) modeling. These approaches accounted for daily fluctuations in eating habits and minimized measurement errors, providing a more reliable picture of long-term dietary patterns. "It was imperative that our analysis used the most rigorous, gold-standard methods to assess usual intake and mortality risk," Phillips explained. "These methods allowed us to account for fluctuations in daily protein intake and provide a more accurate picture of long-term eating habits."

The study's funding came from the National Cattlemen's Beef Association (NCBA), a contractor to the Beef Checkoff program, though the organization had no role in the design, data collection, analysis, or publication of the results. This independence is crucial, as prior studies on meat consumption have sometimes faced scrutiny over industry influence.

While the results are promising, experts caution that observational studies like this one cannot establish causation. "Observational studies are valuable for identifying patterns and associations in large populations, but they cannot prove cause and effect," the researchers noted. Potential protective mechanisms could include the high-quality protein in animal sources, which supports muscle maintenance, immune function, and recovery from illness—factors that might indirectly lower cancer mortality risks. Additionally, animal proteins provide bioavailable nutrients like vitamin B12, iron, and zinc, which are harder to obtain from plant sources alone.

This research contrasts with earlier studies that have linked high red and processed meat intake to increased health risks. For instance, a 2019 Harvard T.H. Chan School of Public Health analysis of over 80,000 participants found that increasing red meat consumption by just half a serving per day raised overall mortality risk by 10%, with processed meats showing even stronger associations. Similarly, the World Health Organization's International Agency for Research on Cancer (IARC) classifies processed meats as Group 1 carcinogens and red meat as Group 2A (probably carcinogenic), based on evidence tying them to colorectal cancer.

However, the McMaster study focused on "animal protein" broadly, encompassing not just red meat but also poultry, fish, eggs, and dairy. This broader categorization may explain some discrepancies, as fish and certain dairy products have been shown in other research to have protective effects against specific cancers. Critics, including epidemiologists from institutions like Moffitt Cancer Center, point out that the findings run counter to meta-analyses of hundreds of thousands of people, which generally support a plant-forward diet for optimal health. "All available evidence suggests that an emphasis on plant-based protein is optimal for health," said Kathleen Egan, ScD, an epidemiologist at Moffitt.

Nutrition experts like Egan also stress that while the study doesn't support fearing moderate animal protein intake, it doesn't advocate for unlimited consumption. Processed meats, in particular, remain a concern due to additives like nitrates and high sodium levels. "Previous research has linked high intakes of processed meat with negative health outcomes like cardiovascular disease and certain cancers," she noted. Recommendations from bodies like the American Cancer Society continue to endorse limiting red meat to no more than 18 ounces per week and avoiding processed varieties altogether.

The study's consistency across demographics—regardless of age, physical activity, or baseline health—adds to its credibility, but further randomized controlled trials are needed to confirm the protective effects. In the meantime, the findings encourage a nuanced approach to protein: balance animal sources with plenty of fruits, vegetables, whole grains, and plant proteins for comprehensive health benefits.

As debates over meat's role in the diet intensify amid growing interest in sustainability and plant-based alternatives, this research underscores the need for personalized nutrition advice. For those concerned about cancer risk, incorporating lean animal proteins like fish and poultry while minimizing processed options could be a practical step, alongside maintaining an overall healthy lifestyle.