Optimize dietary protein to stave off osteoporosis

Thursday, July 21, 2011 by: Andrew Kim
Tags: osteoporosis, dietary protein, health news

(NewsTarget) Decades of research have generated a better understanding of the bone remodeling process, and this improved understanding has paved the way for new mechanism based therapies. One such approach to slow bone degeneration is to prop up the anabolic side of the bone remodeling process through increased dietary protein.

Osteoporosis (OP) is a disease of the bone characterized by decreased mass and distortion of its architecture - not necessarily a disease of decreased mineral density (osteopenia).

There is no doubt that OP has become a major health threat for all ethnicities and sexes. OP affects over 10 million Americans. Most of the afflicted present an absence of symptoms and are unaware that they have OP until they break a bone. Fractures can lead to back pain, loss of height, curvature of the spine, and death.

Bone is continuously remodeled throughout life. Bone metabolism takes place within bone cavities and is controlled by three cell types: Osteoblasts, osteoclasts, and osteocytes - together known as the basic multicellular unit (BMU). The BMU is regulated by many factors - hormones, growth factors, mechanical stress, and plasma calcium - and balance of these factors determines whether bone density will increase or decrease.

Osteoblasts secrete important components of the bone's extracellular matrix or the osteoid. The osteoid is comprised primarily of collagen, along with proteoglycans, osteocalcin, and various phosphoproteins. In other words, the foundational, organic component of bone is constructed from various proteins. Once the osteoid is laid down, mineral crystals are deposited, converting the flexible, organic matrix into hard bone matrix.

It is estimated that between 15-38% of men and 27-41% of women in the U.S. consume less than the RDA for protein (0.8g/kg). In general, as age increases, protein consumption decreases in both sexes. Recent epidemiological studies have demonstrated that individuals with the lowest protein intakes were associated with reduced BMDs and the fastest rates of bone loss.

Increasing dietary protein supports bone health in three main ways: by supplying the raw material required to construct soft bone matrix, by increasing plasma IGF-1, and by promoting muscle growth and retention.

IGF-1 is a growth hormone that stimulates and increases the activity of osteoblasts, the collagen synthesizing cells in the bone. Increased lean muscle mass is the result of consuming protein with high biological value (i.e. animal protein). This is important because bone develops in response to the load it has to bear. So, bone will grow in order to meet the increased demands created by the increased muscle mass.

Burgeoning understanding of the bone remodeling process offers hopeful, non-invasive strategies to delay bone degeneration and stave off deadly fractures. Optimizing protein intake to supply an adequate pool of amino acids to bone that is continuously remodeling is just one untapped strategy.

Sources:

1. Anversa, P. "Aging and Longevity: The IGF-1 Enigma." Circulation Research 97.5 (2005): 411-14.
2. Genaro, Patricia De Souza, and Ligia Araujo Martini. "Effect of Protein Intake on Bone Effect of Protein Intake on Bone and Muscle Mass in the Elderly and Muscle Mass in the Elderly." Nutrition Reviews 68.10 (2010): 616-23.
3. Interaction of Dietary Calcium and Protein in Bone Health in Humans." Journal of Nutrition. Web. 09 July 2011. http://jn.nutrition.org/content/133/3/852S.f....
4. Kerstetter, Jane E., Kimberly O. O'Brien, and Karl L. Insogna. "Low Protein Intake: The Impact on Calcium and Bone Homeostasis in Humans." The Journal of Nutrition 133.3 (2003): 8555-615.
5. Khosla, Sundeep, Jennifer J. Westendorf, and Merry Jo Oursler. "Building Bone to Reverse Osteoporosis and Repair Fractures." Journal of Clinical Investigation 118.2 (2008): 421-28.

About the author

Andrew Kim
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