This is a myth!
Protein does not cause osteoporosis nor declining bone health. In fact, the opposite is true. High quality dietary protein is necessary for strong bones.
Heaney & Layman (2008) examined that bone health depended on a variety of factors:
1) Level of protein in the diet
2) Protein source
3) Calcium intake
4) Weight loss
5) Acid/base balance of the diet.
The review also acknowledged a study of 191 subjects over 20 years that found protein intakes from 0.41 – 1.96 g/kg had no effect on calcium absorption efficiency. No differences in measured markers in the blood for bone turnover were found in either a high protein or high carbohydrate diet.
Studies have shown that various protein sources may exhibit different effects on bone metabolism. It has been shown that:
Animal Source = Higher serum levels of IGF-1
Soy foods/Products = Lower levels of IGF-1.
High levels of IGF-1 are related to bone growth. As individuals age, there are declines in serum levels of IGF-1 concentration.
Both the level of protein and the type of protein in your diet may have an effect of IGF-1 levels in the body.
What about Calcium Intake?
Protein intake increases urinary calcium loss, but whether there is a negative calcium balance, depends on dietary calcium intake.
Highest Protein Intake + Calcium/Vitamin D Supplementation = Positive Bone Health
Take Away Point
High levels of protein do not result in bone demineralization or a decrease in bone mass. High protein diets, rich in calcium help to increase bone mineralization and decrease the risk of fracture.