Can You Eat Too Much Protein?
Have you ever been told that eating too much protein will damage your kidneys?
If someone at the gym told you that you’re eating too much protein and your blood is going to get so acidic that you will damage your kidneys or you get enough protein from veggies so there’s no point to eating meat and risk getting heart disease. Then tell them to go find some published research showing healthy people consuming protein and measuring kidney damage markers. They will find absolutely nothing!
Then why does this myth exist?
Part of the reason is that eating more protein will increase the amount of work your kidneys have to do. Markers such as creatinine (NOT creatine) and GFR (glomerular filtration rate) may go up, indicating that your kidneys are working harder. But does that mean there's any indication of damage? Let's dive in.
From Phillips, SM 2014: "An examination of the statements made by both the Institute of Medicine in setting the protein RDA in North America, as well as the World Health Organization's report on protein intakes, indicates there is no evidence linking a higher protein diet to renal disease."
According to two top agencies, the risk of damage to the kidneys in healthy subjects appears to be slim. So the dangerous-protein myth is not looking good.
In otherwise healthy individuals, there is little evidence that high protein intake is dangerous. However, kidney damage may be an issue for individuals with already existing kidney dysfunction." (Tipton KD, 2011).
Researchers in 2015 found that increasing protein did require the kidneys to do more work; however, it did not do any damage to them (no increase in microalbuminuria, which indicates damage). Your kidneys, like your biceps, will get bigger with more work, but that growth is not from any damage. They were just adapting to the stress placed on them.
But what if you are a powerlifter or body builder and consume a ton of protein?
One of first studies on protein was from Poortmans JR and Dellalieux O. in 2000 who suggested that excess protein is hazardous to the kidneys. This study investigated bodybuilders and other well-trained athletes with high and medium protein intake.
So what did they find? Well, while those who ate a high protein diet did have higher plasma concentrations of uric acid and calcium, the bodybuilders had normal renal clearances of creatinine and urea (waste products). Scientists concluded that protein intake under 2.8 g/kg did NOT impair renal function in well-trained athletes.
Another study was done by Brandle and colleagues in 1996. While the study wasn't perfect, it was the first to look at the effects of protein on kidney function. They found no correlation between albumin excretion rate (urinary albumin arguably being a damage variable) and gross protein intake (as assessed by nitrogen excretion rate).
You could argue that this data is still short term. Most lifters are eating high protein for years to decades. What about 6 months into their high protein eating plan? What happens to their kidneys then? Dr. Jose Antonio again in 2016 published a one year study.
The researchers took fourteen healthy resistance-trained men who'd been training an average of almost nine years and had them consume their normal diet altered with a high protein version (>3 g/kg/d). If you weighed 185lbs, you’d have to consume ~250g of protein per day. That’s approximately 12 chicken breasts. The subjects had to eat that much daily for 1 year.
They found that there were no harmful effects on measures of blood lipids as well as liver and kidney function. Subjects also did not gain fat from all of those extra calories and saturated fats that they were consuming.
Long story short don’t worry about consuming too much protein, worry about not consuming enough!
Reference the full article written by Mike T Nelson, Phd