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Study under review: Animal versus plant protein and adult bone health: A systematic review and meta-analysis from the National Osteoporosis Foundation.
In mid-2017, a systematic review commissioned by the National Osteoporosis Foundation (NOF) was published with the goal of evaluating the relationship between the amount of ingested dietary protein and bone health. Proteins are an essential component of bone tissue, creating an organic structural matrix that provides strength and the groundwork for mineral deposition (mainly calcium, magnesium, and phosphorus).
The NOF systematic review was conducted because of two seemingly contradictory hypotheses, both of which are mechanistically plausible. On the one hand, dietary protein would seem to be beneficial for acquisition and maintenance of bone mass and strength due to its structural role. On the other hand, protein metabolism increases the amount of acids in the blood that affect the blood’s acid-base balance. If this acid-base balance disorder occurs in a prolonged and chronic way, low-grade metabolic acidosis may become significant and contribute to diseases.
Bone is an especially vulnerable tissue to metabolic acidosis because structural bone mineral is dissolved to release bicarbonate to neutralize acid. This process is depicted in Figure 1, and is part of the basis for the “alkaline diet” and its many associated lay-press books. Yet, the NOF systematic review found that protein supplementation did not adversely affect bone health outcomes, including bone mineral density or the risk of falls and fractures. In fact, the NOF review found that eating more protein was beneficial for bone mineral density at the lumbar spine.
Of course, not all protein is the same. Considerable debate remains over the health effects of animal-based proteins compared to plant-based proteins. Animal proteins, for example, tend to be higher in sulfur-containing amino acids such as cysteine, methionine, and taurine, which are believed to be more “acid-producing.” Accordingly, the study under review was a follow-up systematic review commissioned by the NOF to compare the effects of animal vs. plant proteins on bone health outcomes.
Due to concerns that high-protein diets might lower blood pH and therefore increase the breakdown of bone tissue to neutralize acids, the National Osteoarthritis Foundation commissioned a systematic review evaluating the relationship between the amount of ingested dietary protein and bone health. The study under review is a follow-up publication, focusing on the type (animal vs. plant), rather than amount, of dietary protein.
Other Articles in Issue #42 (April 2018)
Interview: Danny Lennon, MSc
We chat with the founder of Sigma Nutrition and combat sports nutritionist Danny Lennon about his background, the unique nutritional challenges faced by combat sports athletes, and two things he thinks everyone can do to improve their lives.
Alpha-lipoic acid for carpal tunnel syndrome
Previous human studies examining ALA have either given it along with other supplements or only administered it post-surgery. This trial looks at ALA's effects on its own, both before and after surgery.
Protein gains: not just for the men
Women are underrepresented in many areas of research. This study focuses specifically on female physique athletes to see how high vs. low protein intake affects fat-free mass.
From French Paradox to plaque regression
Observational data suggests that moderate wine consumption could be heart healthy. This follow-up to a study we covered in a previous NERD puts this hypothesis to the test.
Can whole grains improve insulin resistance in obese adults?
What impact does replacing refined grains with whole grains in a macronutrient-matched diet have on weight loss and glucose regulation? This study aims to find out.
A fishy relationship between omega-3 fatty acids and heart health
We review a recent major meta-analysis which examined only large and long clinical trials to find out whether omega-3’s really affect CVD risk.
Interview: Michael Crosier, PhD
In this interview, we chat with Dr. Crosier about the ins and outs of learning and teaching nutrition and dietetics, his research on vitamin K, and more.