Calcium nutritional requirements

The mean dietary intake of soy isoflavones in Asian populations consuming soy-based diets ranges from 20-40 mg isoflavones/day, with upper percentile consumer intakes of 70 mg/day (corresponding to around 1 mg/kg body weight). In the six month intervention studies in Western postmenopausal women, the effective dose for improved BMD was around 80-90 mg/day, while in the one year, randomized, double-blind, placebo controlled clinical trial, the effective dose was 54 mg/day. Overall, the dietary recommendation is to consume 50 mg isoflavones/day in combination with standard nutritional requirements for calcium and vitamin D. 

The importance of the calcium ion in human physiology is reflected by the emphasis placed on this element in human nutrition, which is important throughout life. When we are young and growing rapidly, adequate dietary calcium is required... 

The RDA for calcium in adults over the age of 24 is 0.8 g. The RDA for women during pregnancy and lactation is 1.2 g. The increased level of 1.2 g is required to supply the fetus with the 30 g of calcium present in the newborn and to provide the 0.24 g of calcium secreted in the milk each day. The RDA for persons from 11 to 24 years of age is 1.2 g the RDAs for children (0.8 g) and infants (0.6 g) are lower. Eggs supply about 30% of dietary calcium and 30% of dietary phosphate for the overall population in the United States. Meat, poultry, and fish supply 20-25% of our phosphate, but only 10% of our calcium. Milk and dairy products supply 20-25% of our phosphate, and 50% of our calcium (Calvo and Park, 1996). A dietary deficiency in calcium is quite rare, though calcium nutrition receives much attention because of mainstream health concerns related to calcium, such as osteoporosis, hypercalcemia, and hypocalcemia. 

Minerals, in the nutritional sense, are inorganic substances required in the ionic or free-element form for life processes. The macrominerals (those needed in the largest amounts) are sodium, potassium, chloride, magnesium, phosphorus, and calcium. The required amounts of all these minerals, except calcium, can easily be satisfied by a normal diet. Deficiencies of calcium can. 

Phosphorus is closely bound up with calcium from both metabolic and nutritional viewpoints. Phosphorus occurs abundantly in plant and animal tissues and, if the other nutritional requirements are satisfied, the diet should contain adequate amounts. Meat, eggs, dairy products and cereals are all good sources. 

Science has found no magic or miracle foods. No one food is a preventive or cure-all for diseases. Foods are important because of their nutrient content and no single food can serve as the source of all the essential nutrients. For example, wheat germ is considered a health food because it is a good source of vitamin E, the B vitamins, calories, essential fatty acids, protein, fiber, and most minerals. However, it lacks calcium, vitamin A, and vitamin C. So, the best way in which to ensure that nutritional requirements are met is to eat a variety of foods from each of the major food groups. 

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

Besides local toxicity, discussed above, there are numerous other modes of potential adverse interactions involving excipients (19,20). Many of these pose little threat provided the amounts of excipients are constrained to certain levels. Excessive amounts, however, can cause problems, particularly for patients who are intolerant of even modest levels. Commonly used phosphate buffers may cause calcium loss with formation of insoluble calcium phosphates when such buffers are administered in over-ambitious amounts (21). Calcium phosphate precipitation has been noted particularly in nutritional parenteral admixtures for neonates because of the high nutrient requirements. Similarly, renal toxicity has been associated with depletion of zinc and other trace metals caused by large parenteral doses of ethylenediaminete-traacetic acid (EDTA) (22). Excessive absorption of glycine solutions, when used as irrigants during transurethral resections, can cause hyponatremia, hypertension, and confusion (23). The use of preservatives has been associated with cardiac effects in a few patients (24). Premature neonates were found to be at risk for receiving toxic amounts of benzoic acid or benzyl alcohol in bacteriostatic solutions used to flush intravenous catheters (25). 

Of the seven macro mineral elements required by dairy cattle, five can be considered fertilizer elements (potassium, calcium, phosphorus, magnesium, and sulfur), but sodium and chloride are both toxic lo plants at high concentrations and present practical problems in areas with saline soils. High salt intakes have also been shown lo increase udder edema in heifers. Because of the importance of chloride in nutrition and mclabolisni. research is needed to define the chloride requirements of lactating cows and clarify mineral relationships, especially between chloride and potassium plus sodium-... 

There arc several unique features exhibited by the D vitamins. First, they are not required nutritionally al all if the organism has access to ultraviolet light (which is present in sunlight). Some animals, kept away from ultraviolet light, require so little D vitamins that the need cannot be demonstrated using ordinary diets. Rats, for example, exhibit a need for D vitamins when the calcium/phosphorus ratio in the diet is about 5 1 but not when it is the more usual 1 1. Chickens, on the other hand, exhibit a need even when the calcium/phosphorus ratio is normal (1.5 1). 

R)-Pantothenic acid (vitamin B5) is synthesized by microbes and plants, but not by mammals, who require it as a nutritional factor. Only the (R)-enantiomer is physiologically active. (R)-Pantothenic acid is produced as its calcium salt on a 6 kt a-1 scale, 80% of which is applied as an animal feed additive major suppliers are Roche, Fuji and BASF. Pantothenic acid is produced via chemical methods [110] but a fermentative procedure has recently been commercialized. 

Not all calcium present in the diet is absorbed by the small intestine and mechanisms are present to ensure only amounts appropriate to body needs are absorbed. These processes are complex and involve the interaction of special transport protein, vitamin D and parathormone. Thus, abnormalities of calcium metabolism may result from many different disease processes. Diseases affecting the bowel may prevent normal absorption, diseases of the parathyroid gland may result in inappropriate levels of parathormone for calcium requirement and a nutritionally inadequate diet may cause vitamin D deficiency with consequent disordered calcium absorption. 

Calcium Effects on Zinc Bioavailability for the Rat and the Human. It should be pointed out at this juncture that the nutrient requirement of calcium for the rat is much higher than for man. In fact, the molar ratio of calcium to zinc in excess of 660 1 is recommended for rat diets, while for man the ratio is between 80 1 and 160 1. To feed rats molar ratios of calcium and zinc similar to human requirements would necessitate either a very calcium deficient diet or one containing zinc at a level well in excess of the requirement. Neither choice is nutritionally suitable for demonstrating an effect of phytate on zinc availability. 

B. About 20 elements are called minerals. They also play a role in human nutrition. The minerals known to be essential for good health are calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iron, manganese, copper, iodine, cobalt, fluorine, and zinc. Traces of sihcon, boron, arsenic, strontium, aluminum, bromine, molybdenum, selenium, and nickel may also be required. These elements are eaten in the form of their compounds, but it does not matter much which compounds. 

---