Acidic diets (high in protein and refined food) will cause bone calcium leaching in order to maintain your blood pH balance. Chronic leeching of calcium from the bones increases the likelihood of osteoporosis. [Am. J. Clin. Nutr. 2001: 73, pp.118-122, Lancet 1968:1, pp.958-959]
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A chronic excess of dietary protein almost certainly taxes the kidneys and leads to gradual degeneration. (Williams, SR Nutrition and Diet Therapy, page 856, "The Aging Western Kidney").
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"An excess of protein creates an acidic pH in your body. In order to neutralize the acidic pH, the body uses calcium as a buffer, drawing the needed calcium from the bone. This process means that if you consume 9 or more ounces of flesh protein a day, your calcium needs increase by about 250 mg per day."
http://cpmcnet.columbia.edu/dept/ob.../nutrition.html
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A High Ratio of Dietary Animal to Vegetable Protein Increases the Rate of Bone Loss and the Risk of Fracture in Postmenopausal Women, Sellmeyer DE, Stone KL, Sebastian A, et al., Am J Clin Nutr. 2001;73:118-122
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Relationship of animal protein-rich diet to kidney stone formation and calcium metabolism.
Breslau NA, Brinkley L, Hill KD, Pak CY.
Center in Mineral Metabolism and Clinical Research, Department of Internal Medicine, Dallas, Texas.
We wished to determine whether different types of dietary protein might have different effects on calcium metabolism and on the propensity for renal stone formation. Fifteen young normal subjects were studied during three 12-day dietary periods during which their diet contained vegetable protein, vegetable and egg protein, or animal protein. While these three diets were constant with respect to Na, K, Ca, P, Mg, and quantity of protein, they had progressively higher sulfur contents. As the fixed acid content of the diets increased, urinary calcium excretion increased from 103 +/- 15 ( +/- SEM) mg/day (2.6 +/- 0.4 mmol/day) on the vegetarian diet to 150 +/- 13 mg/day (3.7 +/- 0.3 mmol/day) on the animal protein diet (P less than 0.02). Despite the increased urinary calcium excretion, there was a modest reduction of urinary cAMP excretion and serum PTH and 1,25-dihydroxyvitamin D levels consistent with acid-induced bone dissolution. There was no change in fractional intestinal 47Ca absorption. The inability to compensate for the animal protein-induced calciuric response may be a risk factor for the development of osteoporosis. The animal protein-rich diet was associated with the highest excretion of undissociated uric acid due to the reduction in urinary pH. Moreover, citrate excretion was reduced because of the acid load. However, oxalate excretion was lower than during the vegetarian diet [26 +/- 1 mg/day (290 +/- 10 mumol/day) vs. 39 +/- 2 mg/day (430 +/- 20 mumol/day); P less than 0.02]. Urinary crystallization studies revealed that the animal protein diet, when its electrolyte composition and quantity of protein were kept the same as for the vegetarian diet, conferred an increased risk for uric acid stones, but, because of opposing factors, not for calcium oxalate or calcium phosphate stones.
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Excess dietary protein can adversely affect bone, Uriel S Barzel and Linda K Massey, Journal of Nutrition, 1998; 128: 1051-1053
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Dietary animal and plant protein and human bone health: a whole foods approach.
Massey LK.
Food Science and Human Nutrition, Washington State University Spokane, 99210, USA.
massey@wsu.edu
Urinary calcium excretion is strongly related to net renal acid excretion. The catabolism of dietary protein generates ammonium ion and sulfates from sulfur-containing amino acids. Bone citrate and carbonate are mobilized to neutralize these acids, so urinary calcium increases when dietary protein increases. Common plant proteins such as soy, corn, wheat and rice have similar total S per g of protein as eggs, milk and muscle from meat, poultry and fish. Therefore increasing intake of purified proteins from either animal or plant sources similarly increases urinary calcium. The effects of a protein on urinary calcium and bone metabolism are modified by other nutrients found in that protein food source. For example, the high amount of calcium in milk compensates for urinary calcium losses generated by milk protein. Similarly, the high potassium levels of plant protein foods, such as legumes and grains, will decrease urinary calcium. The hypocalciuric effect of the high phosphate associated with the amino acids of meat at least partially offsets the hypercalciuric effect of the protein. Other food and dietary constituents such as vitamin D, isoflavones in soy, caffeine and added salt also have effects on bone health. Many of these other components are considered in the potential renal acid load of a food or diet, which predicts its effect on urinary acid and thus calcium. "Excess" dietary protein from either animal or plant proteins may be detrimental to bone health, but its effect will be modified by other nutrients in the food and total diet.
puhetta.. Ihmisen ruoan energiamäärät on vasta tällä vuosisadalla olleet riittävän suuret (esimerkiksi Suomessa vasta sotien jälkeen). Kivikaudellakin 80% ravinnosta oli keräilemällä, eikä metsästämällä saatua, mutta kumminkin silloin kärsittiin aliravitsemuksesta. Aikaisemmin ei myöskään varmaankaan liiemmilti tutkittu munuaissairauksia.
