Fecal calcium excretion dietary

Other methods used to decrease the recurrence of urolithiasis include dietary modifications that decrease calcium excretion and promote diuresis. Changing the diet from alfalfa to grass or oat hay decreases the calcium intake and should decrease the urinary excretion of calcium, since fecal calcium excretion is relatively constant in horses. Although this dietary change should decrease the total calcium excretion, it may also decrease the urinary excretion of nitrogen and the daily urine volume. The latter changes could enhance the supersaturation of urine. In theory, diuresis could be promoted further by the addition of loose salt (50-75 g per day) to the concentrate portion of the diet. However, in one study where ponies were fed sodium chloride (1, 3 or 5% of the total diet dry matter (1% is approximately 75 g sodium chloride for a 500 kg horse)), there were no differences in water intake, urine production or calcium excretion. 

High levels of dietary zinc were associated with marked decreases in bone calcium deposition and in the apparent retention of calcium in male weanling albino rats. Marked increases in fecal calcium levels were also observed in the zinc-fed rats. Excessive dietary zinc was associated with a shifting of phosphorus excretion from the urine to the feces. This resulted in an increase in fecal phosphorus and provided an environmental condition which would increase the possibility of the formation of insoluble calcium phosphate salts and a subsequent decrease in calcium bioavailability. The adverse effect of high dietary zinc on calcium status in young rats could be alleviated and/or reversed with calcium supplements. 

Most of the forementioned studies which examined the influence of various dietary fiber on the bioavailability of calcium by human subjects have depended upon the comparative measurements of calcium content of diets and calcium contents of stools and urine. As reviewed by Allen (3), calcium balance studies have distinct limitations relative to accuracy and precision. However, their ease of application and cost, laboratory equipment requirements, and real (or perceived) safety in comparison to available radioactive or stable isotope methods continue to make their use popular. In calcium balance studies, calcium absorption is assumed to be the difference between calcium excretion in the feces and calcium intake. Usually this is expressed as a percent of the calcium intake. This method assumes that all fecal calcium loss is unabsorbed dietary calcium which is, of course, untrue since appreciable amounts of calcium from the body are lost via the intestinal route through the biliary tract. Hence, calcium absorption by this method may underestimate absorption of dietary calcium but is useful for comparative purposes. It has been estimated that bile salts may contribute about 100 g calcium/day to the intestinal calcium contents. Bile salt calcium has been found to be more efficiently absorbed through the intestinal mucosa than is dietary calcium (20) but less so by other investigators (21). 

Jacobsen, R., Lorenzen, J. K., Toubro, S., Krog-Mikkelsen, I., and Astrup, A. (2005). Effect of short-term high dietary calcium intake on 24-h energy expenditure, fat oxidation, and fecal fat excretion. Int. J. Obes. (Lond.) 29, 292-301. 

In the present study the effect of calcium and phosphorus on zinc metabolism was investigated In adult men by determining metabolic balances of zinc during different intakes of calcium and phosphorus. Three Intake levels of calcium, ranging from 200 to 2000 mg/day, and two Intake levels of phosphorus (800 and 2000 mg/day) were used during a constant dietary zinc Intake of 14.5 mg/day. Increasing the calcium Intake from 200 to 2000 mg and Increasing the phosphorus Intake from 800 to 2000 mg/day had no effect on urinary or fecal zinc excretion nor on zinc retention. absorption studies confirmed... 

Table II shows data of the effect of a high phosphorus Intake on the zinc balance. The phosphorus supplements were given to three patients during different calcium Intakes, namely, during a low calcium Intake of 200 mg per day and during higher calcium Intakes of 800 mg and 2000 mg calcium per day. The phosphorus Intake of the subjects studied was approximately 900 mg per day In the control study and was 2000 mg per day during the high phosphorus Intake. In the control study, during a low calcium Intake and a normal phosphorus Intake of 900 mg per day and a dietary zinc Intake of 17 mg per day, the urinary zinc excretion was relatively high, 1.6 mg/day, the fecal zinc excretion was In the expected range and the zinc balance was positive,...

Calcium in the feces—Calcium is excreted mainly in the feces, most of which is dietary intake that is not absorbed (see Fig. C-4). The remainder, called endogenous fecal calcium (which ranges between 125 and 180 mg per day) comes from shed epithelial cells and the digestive juices (bile and pancreatic juice). As shown in Fig. C-4, approximately 70 to 80% of food calcium is unabsorbed and excreted in the feces. 

Apparent absorption (intake minus fecal excretion) of calcium decreased when the diet contained muffins with added sodium phytate to increase the molar ratio of phytate/calcium from 0.04 to 0.14 and 0.24. One-half of the men excreted more calcium in feces than was consumed when the high phytate diet was consumed. People consuming diets with molar ratios of phytate/calcium exceeding 0.2 may be at risk of calcium deficiency because of low bioavailability of dietary calcium unless physiological adjustments can be accomplished that maintain homeostasis. 

With the typical dietary intake of calcium (800 mg/day), about 20% of the calcium is absorbed. Fecal Ca is about 640 mg/day and urinary Ca is about 160 mg/day. Urinary calcium increases somewhat with an increase in intake. For any given increase, urinary Ca increases by an amount equivalent to about 6,0% of the increase in intake. Fecal Ca consists of the unabsorbed mineral and a small amount of Ca secreted into the gastrointestinal tract (100-150 mg/day). An amount of Ca equivalent to 1 to 6% of the total fecal Ca is excreted in the bile I eGrazia and Rich, 1964). Urinary Ca generally ranges from 100 to 250 mg/day. The Ca lost via the skin is about 15 mg/day, with increased losses occurring in the sweat during work in warm climates. 

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