By Kara McIver, M.S. student in Human Nutrition
While you might think of protein only as the building block of muscles, it is actually found throughout the body in enzymes, cellular channels, and DNA. We don’t store protein, so it is an essential part of any diet. It has been heralded as the key to fat loss, weight maintenance, and overall health; however, Americans eat more protein than almost anyone else and we are still leading in obesity and the co-morbidities that stem from a Western diet including cardiovascular disease and Type II Diabetes Mellitus.
Within the nutrition and exercise worlds, we often debate “how much” protein is necessary, but maybe the more important question should be “from where?” Both plants and animals can provide us with protein and the latest research aims to understand which is more beneficial.
A new investigation from the National Cancer Institute and NIH evaluated the existence of an association between dietary protein source (plant vs. animal) and long-term overall mortality or cause-specific mortality in the U.S. population. This was a longitudinal cohort study, which means that the investigators followed a group of participants over time to understand how their differences–in terms of intake–impact the rates of death overall and death from certain diseases. In this case, they followed 237,036 men and 179,068 women over 16 years, studying nearly 78,000 deaths and stratifying participants into quintiles (five groups) based on the percentage of their daily caloric intake from plant-based protein. The average age of participants was 62.2 (men) and 62.0 (women) and the median percentage of daily energy intake from total protein was 15.3%.
This study found that higher plant protein intake was associated with reduced risk of all-cause mortality, cardiovascular disease & stroke mortality, independent of other factors including sugar-sweetened beverage intake, age at enrollment in the study, smoking status, and education level, which have all previously been associated with increased mortality risks.
Their findings show you don’t have to go vegan to reap the benefits of plant-based protein. A replacement of just 3% of protein calories from animal sources with plant sources was enough to lower overall and cause-specific mortality. This equates to just 60 calories in a 2,000 calorie diet. Specifically, replacing eggs with bread, cereal, and pasta protein lead to risk reductions of 18-45% in men and 20-39% in women (depending on their starting intake group). Swapping grains for red meat lowered mortality 12-30% in men and 13-28% in women. That’s about two eggs or four ounces of ground beef.
This investigation didn’t find significant improvements when it came to cancer or diabetes deaths, however, and more research is needed on the long-term implications of plant vs. animal protein intakes earlier in life. Further, The Gale Encyclopedia of Diets defines a “high protein diet” as 20% or more of the total daily calories coming from protein, much higher than the median intake of this population, which could skew the results to some degree. The type, duration and intensity of physical activity that older adults engage in may also play a significant role in the amount and type of protein necessary for both peak performance and health. Finally, no consideration was taken for the environmental impact of growing or raising our proteins. As is usually the case, more research is needed in the area of plant versus animal protein but the key to optimal health is often variety!
Peer-reviewed by Jonathan Cerna