Last week, I started discussing the versatile role protein plays in the human body and how high protein diets are being prescribed in both sports nutrition and weight management settings (click here to view). As a result, a growing concern exists about the negative health consequences that may arise from eating too much protein. One of those concerns is the over-stressing of the kidneys leading to renal disease and eventually renal failure. This does not seem to be the case in healthy adult populations; however, high protein diets can accelerate the progression in those who already have existing kidney disease.
High Protein Diet Myths Part 2: High Protein Diets are Bad for Bone Health
The metabolism of sulfer containing amino acids (methionine & cysteine) creates a highly acidic environment within the body, resulting in a lower blood pH. If the acidic load is too high for the kidneys to handle, the belief is that the skeleton (a major calcium storage organ) releases calcium to act as a buffer and neutralize the acidic environment. This results in decreased bone mineral density (BMD) and bone mass. This notion is supported by findings of increased 24h-urinary calcium excretion and lower urinary pH after high protein intakes.
Not so fast!
Two of the most recent comprehensive reviews and meta-analysis (published in 2009 & 2011) examining protein intake and BMD found that dietary protein is not harmful to bone health and may actually INCREASE BMD!
The acidic load created by high protein diets are buffered by our lungs (increased ventilation) and kidneys (increased filtration) to keep our blood pH within very narrow normal limits, and the increased urinary calcium does not alter calcium balance (high protein diets usually accompanied by high phosphorus intakes, which retains calcium).
Ok, so we’ve established that high protein diets being bad for bone health is a myth, but what about the part where it might actually increase bone mass?
That’s correct; a small, positive effect of protein supplementation on increased lumbar spine BMD in randomized placebo-controlled trials supports this claim. It is important to note that more recent findings suggest that if calcium intake is inadequate, this positive effect may not be seen (dietary calcium serves as the acidic buffer from high protein diets).
How does protein improve bone health?
Several mechanisms help explain this:
- Increased production of insulin-like growth factor: IGF-1 increases osteoblast activity (bone formation) and may also promote bone matrix mineralization.
- Increases the amount of calcium absorbed by the intestines.
- Suppresses parathyroid hormone production – PTH causes bones to release calcium into blood and kidneys to retain calcium.
- Increasing muscle mass – stronger muscles allow for more effective and heavier weight-bearing, strengthening your bones.
If you would like strategies on how to effectively increase your protein intake without gaining weight, stop into SST and try out our excellent Butts & Guts bootcamp with a complimentary nutritional assessment.
Head Strength Performance Coach SST Burlington
MSc candidate, Physiology & Nutrition