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| Magnesium is vital to bone density in two important ways. Magnesium, like calcium, stores its reserves in the bones. While calcium adds to bone strength, magnesium adds flexibility. When the magnesium in bone decreases, bone crystals become larger and more brittle, therefore susceptible to fracture. In addition, magnesium plays a key role in the regulation of calcium absorption into the bones. Since 1990, increasing evidence has shown that magnesium supplementation may be more critical than calcium supplementation for the process of increasing bone density.
In a two year study published in 1995, Sojka and Weaver found that supplementation with magnesium hydroxide prevented fractures in women's bones and resulted in a significant increase in bone density. In a 1990 review of research, Abraham and Grewal found that calcium supplementation at any dosage by postmenopausal women caused no significant uptake of calcium in trabecular bone, and had only a slight effect on cortical bone. In fact, megadosing calcium created a serious risk of soft tissue calcification under certain conditions. However, they found that when a dietary program emphasized magnesium, along with lifestyle and dietary habits, 19 postmenopausal women on hormonal replacement therapy significantly increased in bone density as compared to a control group.
Bone tissue is approximately 30% organic and 70% mineral in content. The mineral component of bone is 95% hydroxyapatite, with small amounts of magnesium, sodium, floride and chloride. The organic component, called osteoid, is a matrix of collagen and non-collagenous proteins. Osteoid is produced by cells called osteoblasts. Once formed, osteoid takes 25 to 30 days to become mineralized, a process known as bone formation.
Bone tissue is in a constant state of flux called remodeling. Minerals are pulled from the bone for use in biological activities such as digestion. The process, called bone resorption, is carried out by cells called osteoclasts. Ideally, bone remodeling is a balance of bone resorption and bone formation. Bone remodeling is influenced by, among other things, acid-base balance, physical activity, diet, and hormonal balance. Supplementing the diet with magnesium and calcium helps to prevent excessive bone resorption, and build bone density. The recommended dosage of magnesium is usually 250 to 750 mg per day.
Our bodies regulate bone remodeling by monitoring serum calcium levels in the bone. As serum calcium levels decrease, parathyroid hormone is released, activating Vitamin D, which in turn stimulates renal (kidney) absorption of calcium. At the same time, the parathyroid hormone activates osteoblasts and osteoclasts for remodeling. Once optimum serum calcium levels are reached, another hormone, calcitonin, stimulates the renal clearance of calcium.
Other hormones that affect bone remodeling to a lesser extent are estrogens, androgens, progesterones, glucocorticoids, and thyroid hormones.
Inadequate blood magnesium levels are known to result in low blood calcium levels. In addition, magnesium depletion reduces the sensitivity of bone and renal tissue to the parathyroid hormone and reduces the activation of Vitamin D–both vital to bone formation. Research indicates that magnesium controls cell membrane pass-through, regulating the uptake and release of hormones, nutrients, and neurotransmitters. Without enough magnesium, potassium and calcium are lost in the urine and calcium can be deposited in soft tissues such as the kidneys (forming kidney stones), arteries, joints and the brain.
Perhaps the success of magnesium therapy is related to a deficiency of magnesium in the population in general, as was found by Morgan in 1985. Our food production methods deplete magnesium from our soils and, by using phosphorus and potassium rich fertilizers, we actually inhibit plants from absorbing the magnesium that exists. Furthermore, we have made the unilateral decision that minerals in water are bad, and magnesium is removed from our drinking water.
References and Further Reading:
Sojka-JE; Weaver-CM
Nutr-Rev. 1995 Mar; 53(3): 71-4
Volpe-SL; Taper-LJ; Meacham-S
Magnes-Res. 1993 Sep; 6(3): 291-6
Morgan, K., Magnesium and calcium dietary intake of the US population.
Jo Am Coll Nutr, 1985. 4(2): p. 195.
Magnesium Information Sheet
Understanding Osteoporosis and Clinical Strategies to Assess, Arrest, Restore Bone Loss
Deirdre J. O'Connor, N.D.
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