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United States Department of Agriculture

Agricultural Research Service

It Takes More Than Calcium to Keep Bones Healthy
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Curtiss D. Hunt

Remember the Amazing Drumstick Knot Trick in your Junior Magician's Guide that was supposed to you bring instant fame? It called for two chicken drumsticks and soaking one of them in vinegar for two weeks. At the big show in the backyard, you were to let the admiring audience examine the stiff untreated bone, then take it back, and secretly switch it with the pre-soaked bone. Finally, with the sound of a drum roll in the background, you were to tie the soaked bone in a knot, an amazing feat indeed.

This writer does not recall any notable increase in the number of admirers after his drumstick demonstration but does remember that the soaked bone retained its shape and structure even though it had lost its strength. The vinegar removed the minerals and left behind the protein portion that was nearly all collagen fibers.

Calcium and phosphorus are the main minerals in bone and they are joined together there to form spindle- or plate-shaped crystals that are situated in and around the intertwining and interlocking fibers in a fairly orderly fashion. The unique combination of mineral crystals and strands of collagen in a regular order and ratio results in an structure that has enough stiffness to keep the body from collapsing and enough flexibility to keep the bone itself from cracking during the stress of normal exercise. Bone carries out this supporting function even though it is continuously remodeling and replacing itself.

Scientists are increasingly aware that very small amounts of other minerals are required to build and maintain bone. For example, copper is part of an enzyme that acts to interlock the collagen fibers. It somehow helps maintain bone mineral as seen in a recent study with post-menopausal women. Bone loss was greatly reduced in the women who received an extra 3 milligrams of copper, about the weight of three grains of table salt, in the daily diet.  However, this does not mean that eating more and more copper, or any other nutrient, makes bones stronger and stronger. In fact, for each nutrient, there is a unique point that is slightly different for each person beyond which increased intake of that nutrient increases the risk of negative health effects.

Boron is another mineral that may be important to bone health because it acts on vitamin D in the body. For example, when I don't feed chicks enough vitamin D and boron, the amount of vitamin D in the blood falls and the chick bones do not calcify properly; they get rickets. Adding back normal amounts of boron increases the vitamin D in the blood and several symptoms of rickets go away. Other investigators have noted that boron increases the amount of vitamin D in the blood of adult men and women.

Bone disease costs Americans alone billions of dollars yearly. Therefore, research worldwide is aimed at understanding all the factors that affect bone structure and function. For example, scientists at the USDA-ARS Grand Forks Human Nutrition Research Center test to determine the amounts of boron, copper, magnesium, manganese, and zinc found in natural foods that best keep bones healthy. One thing is for sure: a person must eat a varied and well-rounded diet to get enough of all these minerals. For example, boron is concentrated in peanuts, fruits, nuts, and vegetables. The best sources of copper are liver, seafoods, nuts, and seeds. Meat, liver, eggs, and seafoods (especially oysters) are good sources of available zinc, whereas whole grain products contain that mineral in a less available form.

Last Modified: 10/23/2006
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