Sat, Aug-31-02, 10:06
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Forum Founder
Posts: 37,416
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Plan: LC, GF
Stats: 241/190/140
BF:
Progress: 50%
Location: Eastern ON, Canada
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Hmmm ... I checked out the link provided. The site is a personal, non-scientific collection of bits of information gleaned from here and there. Many of the links on that site are broken, and references are scarce or inaccurate.
The quote which is given above followed this paragraph:
Quote:
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However it must be quickly noted here that calcium supplements increase kidney stone risks according to the Annuals of Internal Medicine, March 1997. High normal dietary calcium reduces kidney stones by 35 percent, but high calcium from non-foods - like calcium supplements - actually increase the risk of kidney stones by 20 percent.
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First, I tried the link given there, and it took me to a commercial website selling vitamins and supplements, and nothing about kidney stones or research papers.
So I hunted around on my own. Went to the Annals of Internal Medicine website, and located the article, which was in the April 1 '97 issue, not March ... Comparison of Dietary Calcium with Supplemental Calcium and Other Nutrients as Factors Affecting the Risk for Kidney Stones in Women. There is no mention of protein anywhere in the results of the study.
Quote:
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Results: During 903 849 person-years of follow-up, 864 cases of kidney stones were documented. After adjustment for potential risk factors, intake of dietary calcium was inversely associated with risk for kidney stones and intake of supplemental calcium was positively associated with risk. The relative risk for stone formation in women in the highest quintile of dietary calcium intake compared with women in the lowest quintile was 0.65 (95% CI, 0.50 to 0.83). The relative risk in women who took supplemental calcium compared with women who did not was 1.20 (CI, 1.02 to 1.41). In 67% of women who took supplemental calcium, the calcium either was not consumed with a meal or was consumed with meals whose oxalate content was probably low. Other dietary factors showed the following relative risks among women in the highest quintile of intake compared with those in the lowest quintile: sucrose, 1.52 (CI, 1.18 to 1.96); sodium, 1.30 (CI, 1.05 to 1.62); fluid, 0.61 (CI, 0.48 to 0.78); and potassium, 0.65 (CI, 0.51 to 0.84).
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Please note the very last sentence: - Other dietary factors showed the following relative risks among women in the highest quintile of intake compared with those in the lowest quintile: sucrose 1.52 ... sodium, 1.30 ... fluid, 0.61 ... and potassium, 0.65.
Sucrose?? My my 
Apparently the study was flawed anyway, according to a letter to the editor of the Annals of Internal Medicine, posted in November '97.
Quote:
.... I suggest that Curhan and colleagues overinterpreted their data and that Coe and colleagues were insufficiently critical in analyzing the data. One test of inferences from such observational data is the finding of at least an ordinal relation between dose and effect. This relation is clearly seen for food calcium in Curhan and colleagues' Table 3, with a highly significant downward trend in risk for stone development as calcium intake increases. However, such a relation is not found with supplemental calcium (the authors' Table 4). Only the group with the lowest supplement intake had a significant increase in risk for stones. The groups with higher intakes had no increase at all. Persons showing an increase consumed less than 500 mg of supplemental calcium per day (that is, the type of intake likely to be associated with multivitamin supplements that contain minerals). In contrast, supplement intakes greater than 500 mg/d generally reflect ingestion of true calcium supplements. Thus, if the effect described by Curhan and colleagues is anything other than a chance occurrence, it may reflect some other component of the types of supplements likely to be represented in the low-intake group rather than calcium.
Finally, it may be worth recalling that the standard therapy for the renal stone disease of intestinal hyperoxalosis is precisely a high calcium intake (in the form of calcium supplements). The reason, consistent with the explanation given for the efficacy of dietary calcium, is the complexation of oxalate in the intestine by unabsorbed dietary calcium and prevention of its absorption; this process in turn reduces the renal oxalate burden.
Robert P. Heaney, MD
Creighton University
Omaha, NE 68178
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So it seems that neither animal protein nor calcium supplements taken at sufficient levels have been positively associated with increased risk of developing kidney stones. RDA for calcium is 1000 to 1200 mg per day for adults.
It would also appear that sucrose (table sugar) is positively associated with increased risk of kidney stone formation, even more so than sodium or fluids.
Doreen
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