Dietary components high-protein diets

Dietary calcium has a relatively small impact on urinary calcium (e.g., only 6-8% of an increase in dietary calcium intake will appear in the urine). The major food components that affect urinary calcium are protein, phosphorus, caffeine, and sodium. For each 50-g increment in dietary protein, approximately 1.5 mmol (60 mg) of additional calcium is lost in urine. The higher amounts of phosphorus consumed concurrently with a high-protein diet can blunt, but not eliminate, this phenomenon. Dietary phosphorus (as well as intravenously administered phosphorus) increases PTH synthesis and subsequently stimulates renal calcium reabsorption and reduces the urinary excretion of calcium. Caffeine causes a reduction in renal reabsorption of calcium and a subsequently increased loss of urinary calcium soon after it is consumed. It has been shown repeatedly in animals and humans that dietary sodium, in the form of salt (NaCl), increases urinary calcium excretion. On average, for every 100 mmol (2300 mg) of sodium excreted in urine, there is an approximately 0.6-1 mmol (24-40 mg) loss of calcium in free-living healthy populations of various ages. Because most of the urinary calcium is of bone origin, it is commonly hypothesized that those nutrients or food components that are hypercalciuretic are also detrimental to the skeleton. On the other hand, thiazide medications are hypocalciuric and, as such, may have modest positive effects on bone. 

Many foods obtained from plants contain tannins. These are phenolic compounds that bind proteins, such as mammalian enzymes. It has been shown in vitro that tannic acid significantly reduces the lubricating qualities of human saliva both by decreasing its viscosity and increasing friction [55], This effect depends on the presence of salivary PRPs, which have a high affinity for tannins [56], It has been shown that the introduction of tannins into the diet can stimulate the production of PRPs in the saliva of rats [57], PRPs are a major component of salivary pellicle, and thus it would not be surprising to find that dietary tannins affect the viscosity of pellicle. 

Daidzein and genistein have been most intensively investigated because of their high levels of occurrence in soybean, a widely used animal feedstuff and a component of traditional Asian diets consumed daily in high quantities by Japanese [10] and Chinese populations [8, 11]. The consumption of products derived from soy has, therefore, been considered as the major dietary factor contributing to the lower rates of hormone-dependent diseases, including breast, prostate, and colon cancers and coronary heart disease, in many Asian countries [12-14]. Almost 10 years after Akiyama et al. [15] first identified genistein as a tyrosine protein kinase inhibitor [15], it was entered into clinical chemoprevention trials in 1996 [16, 17], followed by formal human trials as a treatment for acute lymphoblastic leukemia and breast cancer [18-20]. 

Most of the other components of the analyzed diets - total calories, total fat, mono-unsaturated fat, polyunsaturated fat, total protein - were not significantly related to serum cholesterol levels or coronary heart disease incidence rates of the cohorts. Dietary cholesterol was not systematically evaluated. Sucrose intake - significantly correlated with saturated fat intake - was significantly correlated with coronary heart disease incidence (r = 0.78). However, when this analysis was extended beyond simple correlation, with consideration simultaneously to both saturated fat and sucrose, the association between saturated fat intake and CHD incidence remained highly significant statistically, that between sucrose and CHD incidence became insignificant (14). 

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