Replacing 5% of daily energy intake from carbohydrates with animal protein is associated with increased bone mineral density at the total hip, femoral neck, and lumbar spine over a six-year period in both men and women.

When animal protein replaces carbohydrates in the diet, it increases amino acids in the blood, which signals the liver to produce more IGF-I. This hormone activates bone-building cells to make more bone tissue and improves calcium absorption. At the same time, animal protein reduces the release of a hormone that breaks down bone, allowing more calcium to stay in the bones. Carbohydrates, when eaten in excess, raise insulin levels too much, which causes the kidneys to lose calcium and directly slows down bone-building cells. The net result is stronger bones in the hip and spine.