This post by @tednaiman led to some questions about protein safety that were kindly answered by @mackinprof. High protein diets are often promoted for weight loss, muscle hypertrophy, and prevention of sarcopenia. What are the safety questions and what does the research show?
Concern #1. Protein is bad for the kidneys.
No. The basic thought was that since the kidneys “process” the protein, if you eat more, they work harder, so high protein diets are hard on the kidneys. That is not what the evidence shows.
Zhu et al., 2018 showed no benefit in diabetics with kidney disease (unhealthy patients) when put on a low protein diet.
lipidworld.biomedcentral.com/articles/10.11…
Longland et al., 2016 also showed that a higher protein diet actually improved kidney function measures (GFR in healthy patients, unclear if a benefit but certainly did not worsen function).
ncbi.nlm.nih.gov/pubmed/26817506
One noted nephrologist at a conference had us repeat “there is no such thing as a renal diet!”
Concern #2. Protein is bad for the bones.
No. Shams-White et al., 2017 reviewed several studies and found high protein intakes did not have any negative effects on bone health and there was actually a trend towards improved bone health.
ncbi.nlm.nih.gov/pubmed/28404575
Concern #3. Increased protein is bad for the liver and cholesterol.
No. Antonio et al., 2016 showed high protein diet for a year had no negative impact on liver functions or cholesterol.
ncbi.nlm.nih.gov/pubmed/26778925
(Just FYI, only a few days of a bad diet can change liver functions and cholesterol, so 4 months is a good length of time to study this).
Concern #4. You only need so much protein and the rest (up to 50-60%) is turned to sugar.
No. Multiple studies have shown no increase in blood glucose after protein intake.
Yes, the body can make glucose from protein but even after as 12 hour fast (body needs glucose) when fed 23g protein only around 4g sugar is made (Fromentin et al., 2013). A teaspoon of sugar is 5g.
ncbi.nlm.nih.gov/pmc/articles/P…
So what is the primary care perspective? Protein can assist in weight loss, muscle gain, and prevention of muscle loss. In a world of obesity and sarcopenia, a higher intake of protein may be quite beneficial and appears quite safe but nothing is taken for granted.
Tweets not medical advice.
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