Minerals; Calcium , Magnesium, Osteoporosis

Blood Calcium concentration is closely regulated by intake control at the bowel wall, active deposits and withdrawals from bone and close monitoring of the amount the kidney excretes.

If blood calcium drops even marginally, a state of nervous and muscular hyperactivity - tetany - quickly appears. You can induce tetany in a few minutes by hyperventilating. The increased gas exchange in the lung lowers blood carbon dioxide (as dissolved bicarbonate), raises the blood pH, lowers the calcium concentration, and you are shaky, anxious, with hand muscle cramps drawing your fingers into a clenched fist. You may wake up at night after hyperventilating in your sleep with cramps and muscle spasm from abruptly falling serum calcium concentration. Taking extra calcium may not correct the tetany of hyperventilation (especially at night) because the blood pH change is a sudden and powerful controller of calcium concentration, and oral intake of calcium the previous day is not. The solution for hyperventilation tetany is to rebreathe in a paper bag, since this causes rapid re-accumulation of blood carbon dioxide, normalization of the pH and calcium concentration. mario games besplatno.

Osteomalacia, Osteoporosis

Bone stores 99% of body calcium and calcium salts, laid down in a soft protein matrix , are responsible for the hardness of bones. Long-term calcium deficiency leads to bone thinning or osteomalacia. Osteomalacia refers to the reduction of the mineralization of bone.

The problem of demineralization of bone is confused with loss of whole bone tissue (osteoporosis). A high calcium intake and adequate Vitamin D will promote optimal bone mineralization in youth and decrease the rate of bone-mineral loss in the later postmenopausal period. Lack of Vitamin D in children leads to Rickets -soft, poorly mineralized bone that bends easily. In older women, a high plasma level of vitamin D enhances calcium absorption, whereas high sodium, protein, alcohol and caffeine intakes will cause increased urinary losses and negative calcium balance. Other regulatory changes and/or vitamin D deficiency may alter the balance between calcium absorption from the bowel and excretion from the kidney.

The term "Osteoporosis" refers to a loss of total bone mass and not just bone thinning due to calcium deficiency. Bone loss in adults increases the risk of bone fractures and may contribute to the loss of teeth in healthy postmenopausal women. Low bone mass in women is attributed to heredity, estrogen deficiency and lack of regular physical activity.

Osteoporosis is more a problem of disuse atrophy, with age-related reduction of bone growth-factors than of calcium deficiency itself. Women, fearing the stooped posture of old age, are eager to take milk or calcium supplements. TV ads, promoting calcium ingestion, show the degenerating profiles of an aging woman and are deceptive. Women over 50 years of age show the most bone thinning because of deficiency of anabolic sex hormone production, especially estrogen and declining physical activity. In early menopause, estrogen replacement is effective therapy for conserving bone mass in women. Daily,weight-bearing exercise is the best method of maintaining bone-growth at any age.

The best answer to the problem of bone tissue loss, if you rule out daily exercise, would be preventive treatment with hormone replacement, taken from age 45 onward. Cyclic estrogen and progesterone supplementation in post-menopausal women is the currently recommended strategy. Progesterone acts in concert with estrogen to increase bone formation, and decrease bone resorption, with a net increase in bone mass and strength. Low dosage estrogen (0.3 mg/d - day 1 to 25 of arbitrary cycle month), a progestogen (day 16-25), with 1000 mg of Calcium plus other minerals - manganese, copper, zinc - are recommended as part of a treatment program for post-menopausal osteoporosis. Postmenopausal women given calcium alone show progressive bone de-mineralization. Vitamin D is added and doses up to 4000 iu per day have been useful postmenopausal women.

Measuring Bone Mineral Density.

The measurement of bone mineral density is is "a poor way of predicating which woman will suffer from a hip or spinal fracture..." according to Dr. Ken Basset of the B.C. Office of Health technology assessment. An English study ( Law et al Br. Med J,1991:303:453-9) showed that low bone density measurements only identified 6% of women who later suffered fractures. The lifetime risk of hip fracture in women is about 18% and the incidence increases with age. One of the reasons for doing a bone density measurement is to focus attention the need for preventive strategies in postmenopausal women. The test can be replaced by a policy that states that all postmenopausal women need preventive strategies, starting with daily exercise, proper nutrition and optionally, hormone replacement therapy if there are no contraindications.

Biophosphonates

Alendronate (Fosamax) 5.0 to 10.0 mg per day prevents osteoporosis in younger postmenopausal women, an alternative therapy for women who cannot take hormone replacement therapy (HRT) and an adjunctive therapy for women on HRT. The drug also prevents steroid induced osteoporosis should be considered for use in all patients who require long-term steroid therapy.

In multicenter randomized study (Fracture Intervention trial, reported 1998 at the European Congress of Osteoporosis ), Alendronate decreased the rate of hip fractures by 58%( at mean follow-up period of 3.8 years) in postmenopausal women who took 5 mg/day for 24 months then 10 mg per day. In another study, combined therapy with Alendronate 10 mg/day, Vitamin D 4000 iu/day, and 1000 mg Calcium/day had increases in bone density 2-5 times greater at 12 months than women on HRT alone.

Calcitonin (salmon hormone nasal spray) has also been effective in reducing spinal fracture rate in women over a 4 year period; the women already had one spinal fracture- 200 IU per day over 4 years reduced the risk of fracture by 36%. Bone density increases of .7 to 1.6% were observed.

Raloxifene (Evista 60-120 mg/day), an estrogen hormone receptor modulator reduced spinal fracture rates by 38% in a group of postmenopausal women who had one fracture.

Other Minerals

Silicon is another mineral with a potential influence on bone growth. It is essential in many animals for normal bone growth, but is not usually considered in human physiology. Copper and manganese are also essential for normal bone matrix formation, and must be considered in the overall nutrient equation.

Calcium Supplements

Types of calcium supplement vary a great deal. The cheapest, common supplement is Calcium Carbonate ("Tums"), made from limestone, or oyster shells. The range of absorption efficiency is great, 7% to 68% in one study. There are problems with this calcium supplement in large amounts over a long period of time. Calcium carbonate is an antacid which reduces stomach acidity and may interfere with the digestion of food. It causes "rebound" hyperacidity after it leaves the stomach. It blocks its own absorption. It may be poorly absorbed, and bind other minerals and vitamins. Excess calcium is likely to appear as kidney or gall-bladder stones. More soluble calcium compounds are better, but are usually more expensive. Calcium citrate is not soluble. Calcium glycerrophosphate is the most soluble compound and is used in Alpha Nutrition Formulas.

Calcium intake recommendations, to be realistic and effective will have to take into account the type of calcium chosen and the variables of absorption in each individual.

Calcium absorption from GIT is regulated by vitamin D and parathyroid hormones. Without parathormone you cannot actively transport calcium through GIT. In normal circumstances less than 1.0 grams of calcium per day is adequate, but without parathormone, 4-6 grams (calcium citrate) per day may be required along with excessively high doses of vitamin D, up to 50,000 IU per day - 250 times the RDA!

Each mineral works best in proportion to other minerals. Calcium is usually referred to magnesium; and the ratio range should be about 2-1; Ca/Mg. Calcium intake recommendations must therefore take into account the kind of calcium, the amount of vitamin D in the diet, the amount of sun exposure, the activity of parathormone, the dietary intake of binding substances like phytic acid, and competition of calcium with phosphorus, magnesium and other minerals. Deciding calcium intake recommendations, is not simple. There is likely to be a wide margin of error in any general "recommended daily allowance".

Magnesium

Magnesium is a critical ion, regulating nerve and muscle cell function. It also is a co-factor for many enzymes of the energy extraction system, and protein synthesis pathways. The adult RDA is 300-350 mg/day. It is actively and passively absorbed. If active transport fails, dietary requirements rise sharply, analogous to calcium absorption problems. Magnesium is widely distributed in plant and animal foods, so that deficiency usually only occurs with impaired absorption, malnutrition, alcoholism, or diuretic use.

Deficiency symptoms begin with nausea, loss of appetite, edema, fatigue, and progress to major neurological symptoms- tremors, disordered movement, convulsions, and coma. Magnesium and calcium deficiency may predispose to sudden death from cardiac arrhythmia, and ironically, is most likely to occur with diet and diuretic therapies for hypertension and heart disease.

Magnesium deficiency also occurs in chronic alcoholism from Mg loss in the urine, exacerbated by low dietary intake, gastrointestinal losses with diarrhea or vomiting. Osteoporosis is prevalent in the alcoholic population. Mg deficiency may contribute to increased bone loss; hypocalcemia is associated with low magnesium due to impaired parathyroid hormone secretion and resistance to PTH action. Serum concentrations of vitamin D are also low. Hypomagnesemia in alcoholics may also contribute to increased cardiovascular disease by enhanced platelet aggregation which can be corrected with Mg therapy. Mg inhibits the synthesis of thromboxane A2 and 12-hydroxyeicosatetraenoic acid, eicosanoids thought to be involved in platelet aggregation. Mg also inhibits the thrombin-induced Ca2+ influx in platelets, as well as stimulates synthesis of prostaglandin I2, a potent antiaggregatory eicosanoid.

Magnesium supplementation should be considered for every patient on diuretics, and patients with cardiovascular disease - hypertension and increased risk of heart attacks. Magnesium replacement is essential for alcoholics and increased doses are given during withdrawal from alcoholic beverage intake. Magnesium supplements in the range of 5 mg/kg/day or 300-500 mg/day for the average adult may be desirable.

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