For their high calcium content, dairy products have long been heralded for building strong bones and preventing osteoporosis. However, concern over high saturated fat, lactose intolerance and other aspects of dairy products and their health implications have fueled a controversy over the relative merits of dairy in the diet.
Moderation
According to the Harvard School of Public Health, currently, the optimal source of calcium is not clear and there is no evidence to show that consuming more than one serving of milk per day will decrease risk of fracture. Additionally, concerns about elevated ovarian and prostate cancer risk from milk consumption may offset the bone health benefits. Instead of increasing dairy consumption, other calcium sources, such as dark green leafy vegetables, dried beans and legumes can round out calcium intake without increasing other risk factors.
U.S. Guidelines
The U.S. National Dairy Council, in a report published in the April 2006 "Journal of Dairy Science" noted that dairy products reduce risk of osteoporosis by promoting increased bone density and slowing age-related bone loss. The authors cited a large body of scientific evidence in support of the 2005 Dietary Guidelines for Americans that recommend three servings of dairy products per day.
Pediatric Studies
A review of literature on the merits of dairy products for bone health in children and young adults found scant evidence to support increased use of dairy products to promote bone density. The U.S. study, published in the March 2005 "Pediatrics," reviewed 58 previously published research studies and found no association between dairy consumption and bone health.
Whey Protein
Whey protein -- the portion of milk protein that is removed in the making of cheese from cow's milk -- stimulated bone growth in a Chinese study published in the July 2009 "Journal of Dairy Science." In the study, which used tissue cultures of bone cells, levels of bone-producing cells, known as osteoblasts, increased. Additionally, osteocalcin -- a protein that regulates the mineral composition of bone and insulin-like growth factor -- a group of small proteins that influence bone growth, also increased in the osteoblast tissue culture. The results of the study indicate that whey protein may play an important role in osteoporosis prevention.
Protein
Countries with the highest dairy production also have the highest rates of osteoporosis, according to the Michigan State University website. Conversely, low rates of osteoporosis are often observed in countries and cultures where the average individual consumes less than 500 mg of calcium daily, and many consume no dairy products, whatsoever. A theory for the inverse association between calcium consumption and osteoporosis is that osteoporosis is not directly related to calcium consumption. Instead, a theory being explored by some experts, according to the U.S. Department of Agriculture, is that high dietary protein levels are associated with decreased bone formation. Over time, a high-protein diet leads to lower bone density and an increased predilection for osteoporosis.
References
- Harvard School of Public Health: The Nutrition Source - Calcium and Milk: What's Best for Your Bones and Health?
- Pub Med:Effect of whey protein on the proliferation and differentiation of osteoblasts
- Pub Med: Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence
- Pub Med: Major scientific advances with dairy foods in nutrition and health
- Michigan State University: Why Milk Won't Prevent Osteoporosis
- USDA: Boning Up on Osteoporosis
