I will discuss 2 articles on this topic for this blog:
High protein diets are helpful with weight loss but there has been a concern that high protein diets can be damaging to the kidneys. This first article, published in America Journal of Clinical Nutrition, asked whether a particular type of high protein in the diet is better than another for you, and how these may affect the kidney over time. This large study had 11,000 participants followed overt time with questionnaires about their diet and tests documenting kidney function.
The results show that a high protein diet is not harmful to the kidneys, whether it is from animal or from plant protein. The high protein diet is associated with leaner body (lower body mass index and waist circumference) and better cholesterol profiles (higher HDL). [First published July 27, 2016, doi:10.3945/ ajcn.116.133819 Am J Clin Nutr]
The second study asked if there is a correlation between the type of protein in the diet and risk of early death. According to an article written by Dr. Mingyang Song and published in Journal of the American Medical Association on August 1, 2016, people who get more of their protein from plant sources have lower risk of dying prematurely than those who consume more animal protein. The data comes from analysis of two large US studies comprising 131,342 individuals whose diets were monitored for up to 3 decades. The calorie intake averaged 14% animal protein and 4% plant protein.
The results showed that there was an increased risk of death linked to higher animal protein intake only for people with unhealthy lifestyle traits like obesity, heavy drinking, smoking, or lack of exercise. The animal higher animal protein diet did not harm participants who had a healthy lifestyle.
The study also found that there was a spectrum of how the type of protein in the diet affected risks. Switching 3% of calories from animal protein to plant protein lowered overall risk of earlier death, based on the type of animal protein being substituted. Risk of dying early decreased by 30% if people ate less processed red meat (cold cuts, sausages, beef jerky, ect) by 12% for less unprocessed red meat, and by 19% for fewer eggs.
So what I get from this is that for people who have risk factors for heart disease and unhealthy lifestyle having a predominance of plant protein, fish and chicken are best. Consuming less eggs and dairy is helpful. Even more beneficial is avoiding red meats altogether. It appears that healthy people have more flexibility with their choice of protein.