Author
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Roughead, Zamzam |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 10/1/2004 Publication Date: 12/1/2004 Citation: Roughead, Z.K. 2004. Dairy protein and bone health [abstract]. International Dairy Federation (IDF) World Dairy Summit. p.47. Interpretive Summary: Technical Abstract: Osteoporosis is a complex metabolic bone disease which currently affects 200 million people worldwide. The incidence is expected to increase as our life expectancy and the number of elderly individuals rises around the globe. To date, no cure for this debilitating disease exists. With recent adverse findings of the Women's Health Initiative, the already low compliance with prophylactic hormone replacement therapy is expected to decline further. Thus, changes in dietary practices which offer a safe, sensible, food-based, and low cost approach to reduce the risk and prevent osteoporosis have become even more desirable than in the past. However, defining dietary practices that optimize bone health has been difficult because of complexity of bone as an organ system, and of food as an equally complex vehicle of nutrients and non-nutrients. Bone is a composite material with both organic and inorganic components. By weight, bone is 70% mineral, 5-8% water, and the rest is organic material. The inorganic phase of bone is about 95% calcium-phosphate (hydroxyapatite crystals); the organic phase is about 98% type I collagen with a variety of noncollagenous proteins including important regulatory proteins, cytokines and growth factors. Therefore, it is logical that calcium, phosphorus and protein have been targeted as nutrients for which an adequate intake is thought to be necessary for bone formation, growth and maintenance. Dairy foods are known to be an excellent source of all three nutrients. While calcium and phosphorus in dairy foods are considered beneficial to bone health, the high animal protein content is often considered to be detrimental. Diets high in animal protein are hypothesized to tap into the alkali reservoir in bone; cause gradual dissolution of bone mineral; and are considered a risk for excessive urinary calcium loss and thus osteoporosis. This concern is based primarily on evidence from studies using purified proteins in which a clear hypercalciuric effect has been established. However, the effect of common sources of protein on calcium retention is controversial. This presentation will include recent data from several carefully controlled feeding studies, at the USDA-ARS, Grand Forks Human Nutrition Research Center, in which the effects of dietary protein source (animal protein and vegetable protein) and quantity (high versus low) on calcium retention and bone metabolism have been determined. Using careful study designs which include controlled diets of several weeks' duration, randomized crossover design, and sensitive radiotracer/whole body counting methodology, the data indicate that a high animal protein intake improves calcium retention, especially when calcium intake is low. The presentation will also include recent data from GFHNRC indicating that a high protein intake may play a role in the prevention of somatopause, the age-related decline in serum IGF-1. |
