Calcium dietary requirements

Example 1.—A classical problem of linear programming is the diet problem. Given minimal needs for vitamins, iron, calcium, phosphorous etc., which are present in known proportions in a variety of possible foods with given prices, it is desired to determine a diet from these foods that meets the minimal needs for the vitamins and other ingredients at the lowest cost. To illustrate with a simple example and hypothetical figures, denote three types of food by Flt F2, F3, and two types of dietary requirements, e.g., vitamins by A and B. The table... 

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... 

Administration. Most children and adults do not ingest sufficient dietary calcium and require supplements (see Tables 88-5 and 88-6). Individuals with certain characteristics or conditions—such as lactose intolerance nondairy vegetarian diet malnutrition low-fat diets and glucocorticoid, antiresorptive, or parathyroid therapy—also require evaluation for calcium supplementation. To ensure adequate calcium absorption, 25(OH) vitamin D concentrations should be maintained in the normal range." ... 

Calcium and phosphorus are major minerals that are needed for the development of healthy bones and teeth. These two minerals are found in a crystalline calcium phosphate mineral known as hydroxyapatite, [Cajo(P04) (OH)2l, that makes up the mineral matrix of bone and teeth. In addition, calcium is required for normal blood clotting and muscle function. The RDA for calcium is 1200 mg/day for adults between nineteen and twenty-four years of age and 800 mg/day for adults over age twenty-five. Milk, cheese, canned salmon, and dark green leafy vegetables are all rich sources of dietary calcium. 

The net requirement of a mineral element for maintenance plus growth is calculated as the sum of the endogenous losses and the quantity retained. To determine the dietary requirement, the net requirement is divided by an average value for availability. For example, a 300 kg heifer gaining 0.5 kg/day might have an endogenous calcium loss of 5.0 g/day and be retaining 6.0 g/day. Its net calcium requirement would therefore be 11.0 g/day. For an animal of this type, the availability of calcium is predicted to be about 0.68 and the daily calcium requirement would be calculated as 11.0/0.68 = 16.0 g/day. 

Needs for infants increase from month to month with size and activity. The amounts given are for approximately 6 to 8 months. The dietary requirements for some of the nutrients such as protein and calcium are less if derived largely from human milk. 

Man s dietary requirements for vitamin D cannot be stated simply. The sun s rays acting on the skin produce vitamin D under some conditions this process may supply all that is needed, and no dietary source is required. The amount needed, regardless of source, is influenced by the intake of calcium and phosphorus, although the exact function of vitamin D is still not clear (Nicolaysen and Eeg-Larsen, 1953). The administration of vitamin D during pregnancy does not obviate the need for... 

The active component in one type of calcium dietary supplement is calcium carbonate. A 1.2450 g tablet of the supplement is added to 65.00 mL of 0.4984 M HCl and allowed to react. After completion of the reaction, the excess HCl(aq) requires 38.45 mL of 0.2257 M NaOH for its titration to the equivalence point. What... 

The amount of each element required in daily dietary intake varies with the individual bioavailabihty of the mineral nutrient. BioavailabiUty depends both on body need as deterrnined by absorption and excretion patterns of the element and by general solubiUty, and on the absence of substances that may cause formation of iasoluble products, eg, calcium phosphate, Ca2(P0 2- some cases, additional requirements exist either for transport of substances or for uptake or binding. For example, calcium-binding proteias are iavolved ia calcium transport an intrinsic factor is needed for vitamin cobalt,... 

One method of treatment is to inject calcitonin, which decreases blood Ca " concentration and increases bone calcification (33). Another is to increase the release of calcitonin into the blood by increasing the blood level of Ca " ( 4). This latter treatment is accompHshed by increasing Ca " absorption from the intestine requiring dietary calcium supplements and avoidance of high phosphate diets. The latter decrease Ca " absorption by precipitation of the insoluble calcium phosphate. 

Vitamin D is not strictly a vitamin since it can be synthesized in the skin, and under most conditions that is its major source. Only when sunlight is inadequate is a dietary source required. The main function of vitamin D is in the regulation of calcium absorption and homeostasis most of its actions are mediated by way of nuclear receptors that regulate gene expression. Deficiency—leading to rickets in children and osteomalacia in adults—continues to be a problem in northern latitudes, where sunlight exposure is poor. 

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 concept of bioavailability was developed to explain the difference between the total amount of mineral in a food and the amount which was used by the individual consuming the food. Over the past sixty years or more, there have been numerous studies related to dietary calcium requirements and bioavailability (1,2). As a result, much is known about non-calcium food components which influence the absorption and utilization of dietary calcium under experimental conditions. What now is lacking is a detailed knowledge of how these factors interact with calcium under normal conditions of ingestion in meals. 

We have not completed the analyses of self-chosen diets consumed by the subjects in HS-II and HS-III, but preliminary indications are that there was a wide range in intakes of calcium and of phytate/ calcium molar ratios. Stools and urine were collected while the self-chosen diets were being collected. Comparison of calcium metabolic balance parameters when consuming the self-chosen diets and the controlled diets of HS-II may provide an insight on dietary calcium requirement by these individuals. Some advocate the present RDA of 800 mg for adult men is too low (17), however, unpublished (R.D. Reynolds et al.) data from dietary intakes in a developing country indicate much lower usual intakes of calcium with relatively high phytate/calcium molar ratio. 

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