Animal Versus Plant Protein: No Big Differences for Mortality

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Neither animal nor plant protein intake was linked to heart disease deaths, according to research published in Applied Physiology, Nutrition, and Metabolism. Results also showed a slightly lower risk of cancer death among those who ate more animal protein.

The current recommendation for protein intake is 0.8 grams of protein per kilogram of body weight per day, with 10% to 35% of calories linked to this macronutrient. However, there is still controversy surrounding how much protein is safe and where it is coming from, with some research demonstrating an increased risk of cancer and cardiovascular disease among people who ate higher animal protein intakes. Other studies found plant protein could provide health benefits, while others noted a link between reduced mortality risk and increased protein intake regardless of source.

“There’s a lot of confusion around protein — how much to eat, what kind and what it means for long-term health,” said study author Stuart Phillips, Ph.D., professor in the Department of Kinesiology at McMaster University. “This study adds clarity, which is important for anyone trying to make informed, evidence-based decisions about what they eat.”

Investigators used data from nearly 16,000 U.S. adults to see how protein intake and IGF-1 levels (a growth-related hormone) might affect the risk of dying from any cause, cancer or heart disease. They collected information from the Third National Health and Nutrition Examination Survey (NHANES) between 1988 and 1994 and followed them through 2006. The team specifically compared animal protein (such as meat, dairy and eggs) and plant protein (including beans, nuts, grains and vegetables).

The National Cancer Institute (NCI) method and multivariate Markov Chain Monte Carlo (MCMC) modeling were employed to strengthen their research and ensure reliable results.

“It was imperative that our analysis used the most rigorous, gold standard methods to assess usual intake and mortality risk,” stressed Phillips. “These methods allowed us to account for fluctuations in daily protein intake and provide a more accurate picture of long-term eating habits.”

Key Findings

• Overall death risk (all-cause mortality): Eating more animal or plant protein did not change the overall risk of dying.
• Heart disease deaths: Neither animal protein nor plant protein was linked to higher or lower risk of dying from cardiovascular disease.
• Cancer deaths:
  • People who ate more animal protein had a slightly lower risk of dying from cancer.
  • Plant protein intake did not affect cancer-related mortality.
• IGF-1 hormone levels: Higher or lower IGF-1 concentrations were not linked with risk of death from any cause, cancer or heart disease.
• Across age groups: Results were the same for younger adults (<65) and older adults (>65, or 50 to 65 years).

Even though this study didn’t find a mortality benefit, plant-based protein remains important for heart health, digestion and overall wellness in other research.

While animal protein wasn’t linked to increased risk, age, smoking and sedentary lifestyle were associated with an increased all-cause risk of death.

Investigators noted some important limits to keep in mind. The team didn’t compare protein with other nutrients or explore what might happen if people swapped one nutrient for another. They only measured IGF-1 in a smaller group, so the number of deaths studied was lower than the total group, but still enough to give meaningful results.

Additionally, the study relied on people reporting what they ate, which can sometimes be inaccurate because people often underreport how much they eat. Investigators used advanced statistical methods to try to correct for these issues, but it’s not perfect.

“When both observational data like this and clinical research are considered, it’s clear both animal and plant protein foods promote health and longevity,” said lead researcher Yanni Papanikolaou, MPH, vice president of Nutritional Strategies.