- A new study has found no increased death risk from eating plant or animal protein.
- The findings also suggest that animal protein may slightly lower cancer-related death risk.
- Nutrition experts say there’s no need to alter general protein recommendations, but individual needs may vary based on age, activity level, health status, or dietary pattern.
For decades, the question of whether animal protein is harmful has sparked debate.
Some studies have suggested that eating a lot of meat, eggs, or dairy might increase the risk of death from cancer or heart disease.
On the other hand, plant protein has been praised as a safer and healthier option.
The findings of this study come from the Third National Health and Nutrition Examination Survey (NHANES III), which gathered information from more than 15,000 American adults between 1988 and 1994.
Participants were 19 years or older at the time of enrollment and were followed for 12 years to track mortality outcomes.
During this follow-up period, researchers recorded deaths from all causes, including cancer or cardiovascular disease.
The authors noted that measuring protein intake accurately is a challenge, since diets change from day to day, and surveys that rely on food recall are prone to error.
To address this, the research team used an advanced statistical approach known as the multivariate Markov Chain Monte Carlo (MCMC) model.
This method helps estimate a person’s “usual” nutrient intake by adjusting for normal daily variation and common reporting mistakes.
Using this method allowed the investigators to distinguish between protein coming from animal sources — such as meat, dairy, and eggs — and protein coming from plant sources, including beans, nuts, and grains.
The study went a step further by incorporating blood measurements of insulin-like growth factor 1 (IGF-1).
This hormone has attracted attention in earlier studies, where higher levels were sometimes associated with cancer development and greater mortality risk.
By looking at IGF-1 alongside dietary data, the researchers were able to explore whether the hormone helped explain any potential connection between protein intake and death rates.
Because many lifestyle factors also influence health outcomes, the analysis adjusted for age, sex, smoking, physical activity, and total calorie intake.
These adjustments are important for teasing apart the role of protein itself rather than mistaking other behaviors for dietary effects.
After examining years of follow-up data, the researchers found no evidence that eating more animal or plant protein increased the risk of dying early.
This was true when considering overall mortality as well as deaths caused specifically by cancer or cardiovascular disease.
The results even suggested a small protective effect: participants with higher animal protein intake showed a slightly lower risk of dying from cancer.
When IGF-1 levels were factored in, the story did not change. No significant relationship emerged between this hormone and the risk of death, contradicting some earlier concerns.
The consistency of the results across age groups also stood out. Whether participants were younger adults under 65, older adults over 65, or in the 50-to-65 range, protein intake was not associated with an elevated risk of mortality.
This detail is notable because prior studies had suggested that middle-aged adults might face more danger from higher protein diets.
The research team additionally compared their findings with earlier work that reported strong links between protein and mortality.
They speculated that differences in methodology may explain the contrasting results. Whereas older studies often relied on less precise ways of estimating intake, this analysis used more advanced modeling techniques to better capture long-term dietary patterns.
In addition, the study’s balanced group sizes helped reduce bias that can occur when too few participants fall into certain categories.
Taken together, the evidence suggests that usual protein consumption, regardless of source, does not shorten life expectancy.
By accounting for both dietary variation and biological markers like IGF-1, the researchers provided one of the more thorough examinations to date of the relationship between protein and mortality in a large, nationally representative population.
Avery Zenker, a medical and health writer with MyHealthTeam, said that, based on these findings, people don’t need to make any adjustments in planning their daily protein intake. Zenker wasn’t involved in the new study.
“This study found that going beyond the minimum
“Plan protein intake based on individual goals, including muscle maintenance [and] growth, health needs, and satiety,” she added.
Zenker said the main takeaway from this study is not to fear higher total protein intakes when it comes to cancer or cardiovascular disease risk.
“It doesn’t mean that all protein sources are made equal, though,” she said. “Previous research has linked high intakes of processed meat with negative health outcomes like cardiovascular disease and certain cancers.”
She further noted the importance of not taking these findings as “rules.”
“As with most nutrition research, correlation does not always indicate causation,” cautioned Zenker, explaining that the way the study was structured can make it difficult to exclude other factors that might be influencing the results.
However, this study does contribute to our overall understanding of optimal eating patterns, she said.
Finally, Zenker pointed out that protein sources are not just composed of protein.
There are “many other compounds in protein foods that impact health, like vitamins, minerals, fiber, fats, carbohydrates, and phytonutrients,” she said.
Of course, there is no one-size-fits-all recommendation for protein consumption.
“In addition to the information provided in this study, we also know that certain groups may need to adjust their protein intake based on their circumstances and lifestyle,” explained Maura Donovan, a board certified sports dietitian and Medical Education Specialist for Sports Nutrition at Thorne. Maura wasn’t involved in the study.
Donovan said older adults can benefit from a higher protein intake. This can help them maintain muscle mass and daily function as they age.
“[Athletes] have increased protein needs due to the need for quick muscle repair and recovery after physical activity,” she added.
“Additionally, individuals recovering from illness or injury can benefit from additional protein for immune support, and vegetarians and vegans should combine different plant sources to ensure they’re receiving a complete amino acid profile,” Donovan advised.
Working with a registered dietitian is a good way to figure out your own personal needs. The Academy of Nutrition and Dietetics maintains a database of certified nutrition experts in your area.
