Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In 2019, Dr. David Katz and colleagues, including one of my favorite researchers, David Jenkins, published a public health case for modernizing the definition of protein quality. The prevailing definition seems to have more to do with biochemistry than the net effects on human health. The popular concept that protein is good, and the more the better, coupled with a protein quality definition that favors animal protein, fosters the impression that eating more meat, eggs, and dairy is desirable and preferable. But this is directly opposed to nutrition guidelines that are instead trying to push more plants. Although protein malnutrition is still prevalent in many areas of the world, it is exceedingly rare in the industrialized world, where the most formidable public health threat is not something like kwashiorkor—protein/calorie malnutrition—but from chronic diseases.

And in 2016, a landmark study was published out of Harvard, involving more than 100,000 men and women, that found that replacing animal protein with plant protein was associated with lower risk of dying prematurely. The worst seemed to be processed meat like bacon, as well as egg protein (the egg whites), but swapping in even just 3 percent plant protein for any of the animal proteins: processed meat, unprocessed meat, chicken, fish, eggs, or dairy was associated with a significantly lower risk of arguably the most important endpoint of all, death.

Yeah, but how do we know it’s the protein? The researchers adjusted for factors such as saturated fat intake, which suggested it wasn’t just the animal fat. Okay, but how does your body even know the difference between protein from a plant and protein from an animal? Isn’t protein, protein? No, unlike animal protein, plant protein is generally low in branched-chain amino acids, for example, and decreased consumption of branched-chain amino acids improves metabolic health. It could be the IGF-1, a cancer-promoting growth hormone that is boosted by so-called high-quality animal protein intake though. We suspect the IGF-1 connection is cause and effect, since people who are just born to have higher IGF-1 levels, regardless of what they eat, do appear to suffer higher rates of killers like type 2 diabetes and heart disease.

Or, it could be something the Harvard researchers didn’t control for, such as toxic pollutants, such as dioxins and PBCs, since they tend to accumulate up the food chain into cattle, pigs, chickens, and fish––and therefore end up on our plates. So, plant-based protein also stands as an important step to lower the body burden of harmful pollutants.

If you don’t think 100,000 people are enough, how about 400,000 people? The NIH-AARP study is the largest diet cohort study in history. And again, simply swapping 3 percent of calories from various animal protein sources with plant protein was associated with 10 percent decreased overall mortality. And you get even twice that benefit if you get rid of eggs, too. That’s not a surprise, since egg consumption is associated with a higher risk of developing cardiovascular disease.

Put all the studies together on dietary protein intake and mortality, and people who eat more protein tend to live shorter lives. But this is mainly driven by a harmful association of animal protein. Plant protein intake is inversely associated with mortality––meaning those who eat more plant protein tend to live longer lives. More animal protein may mean more mortality, whereas more plant protein is correlated with less mortality. So, the best of both worlds would be to increase the intake of plant protein in place of animal protein. In other words, as another 2020 meta-analysis concluded, “Persons should be encouraged to increase their plant protein intake to potentially decrease their risk of death.”

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