The most recent study to make headlines is an impressive bit of work that compares longevity and mortality rates between people who eat primarily plant protein with those who primarily eat animal protein. The findings, as touted, say that red meat eaters have a higher mortality rate and that people can have a lower risk of dying by swapping to more plant-based proteins like beans and legumes. Beneath these easily-digestible sound bites lies a bit more nuance that is needed to properly understand what the findings actually say.
First, the basic facts. The study made use of data obtained during prior nation-wide analysis projects and examined 131,342 people overall. Protein intake was measured as a percentage of total daily energy intake, which was 14% for animal protein and 4% for plant protein on average. It was found that, for every additional 10% of energy from animal protein, mortality rates for cardiovascular disease (CVD) rose about 8%.
Conversely, every 3% increase in plant protein was connected to a 10% drop in deaths from CVD. When death from any sources was compared, it was found that substituting 3% energy from plants for the equivalent from red meat could increase longevity by up to 44%. Before you start trading hamburgers for salads, however, a few things need to be kept in mind for context.
The CVD Changes Were Not Universal
The study specifically mentions that the change in death rates from cardiovascular disease was only observed when looking at people who had at least one of a set number of unhealthy lifestyle factors. Unless a person was overweight, obese, a smoker, physically inactive, or a heavy drinker, the amount of animal or plant protein they ate didn’t show a connection to CVD deaths.
The Exact Protein Source Matters
The all-cause mortality findings are impressive, but the biggest change was only seen when plant protein was swapped for processed red meat. Much smaller improvements, in the 10% range, were seen when plant protein was swapped for eggs and unprocessed red meat, and wasn’t seen when looking at chicken or fish.
The Actual Cause for the Longevity Difference Isn’t Identifiable
It is important not to confuse correlation with causation, especially in studies like this one. As the authors note, it is possible that the protein intake is indicative of other lifestyle factors that are the primary cause of the findings.
People who are health conscious and mindful of their food tend to prefer fish and chicken to steak or bacon, for instance. Such people are also more likely to eat in moderation, exercise, or engage in other activities that can improve their longevity. Although the authors tried to control for factors like this in their data, the limits of the study’s structure mean its influence can’t be discounted.
The study does a good job of showing correlations between plant protein, animal protein, and mortality rates even if the exact causes for the longevity difference aren’t as clear. At the very least, the findings are another bit of evidence that it’s important to be mindful of where you’re getting your nutrients from and that simple substitutions, like going for a chicken breast instead of a sirloin, can help your overall health.
Song, M., “Association of Animal and Plant Protein Intake with All-Cause and Cause-Specific Mortality,” JAMA Internal Medicine, 2016; 10.1001/jamainternmed.2016.4182.