The claim that high-protein diets are detrimental to bone and kidney health is a pervasive myth. This article delves into the scientific literature to debunk this misconception. Let’s first address the concern about bone health.
The myth originated from a 1920 study published in the Journal of Biological Chemistry, suggesting a link between increased protein intake and higher calcium excretion in urine. Later, studies in the 1970s and 80s seemingly corroborated this, observing increased urinary calcium even with controlled calcium intake. This led to the “acid ash hypothesis,” proposing that excess amino acids from protein create an acidic environment in the body, prompting the release of calcium from bones to neutralize it, potentially leading to osteoporosis.
However, the flaw lies in the earlier studies’ inaccurate assumption that protein didn’t influence intestinal calcium absorption. A 2017 systematic review by the National Osteoporosis Foundation revealed that increased dietary protein actually enhances calcium absorption, accounting for the rise in urinary calcium. This means the extra calcium in urine comes from improved absorption, not bone loss.
Furthermore, the National Osteoporosis Foundation emphasizes that protein constitutes 50% of bone volume. Current evidence suggests no adverse effects of higher protein intake on bone health. In fact, studies indicate positive correlations between protein consumption and bone mineral density, particularly in the lumbar vertebrae.
Now, let’s address the kidney health myth. This stems from the valid observation that increased protein intake can exacerbate kidney dysfunction in individuals with pre-existing kidney issues. However, this doesn’t imply that protein causes kidney problems in healthy individuals.
A 2015 review in the Journal of Applied Physiology, Nutrition, and Metabolism found no basis for the belief that higher protein intake causes renal failure in healthy individuals. Instead, increased protein intake can lead to a higher glomerular filtration rate (GFR), indicating improved kidney function.
The World Health Organization also confirmed this in 2007, acknowledging the negative impact of high protein on existing kidney disease, but refuting the notion that reducing protein intake protects against age-related GFR decline in healthy individuals. In conclusion, high protein diets do not appear to increase the risk of bone loss or kidney dysfunction in healthy individuals. Instead, they might offer benefits for bone health, muscle mass retention, body composition, and appetite control.
