Posted by noa on May 1, 2003, at 19:39:00
In reply to Re: Magnesium and Calcium Questions » noa, posted by JLx on April 30, 2003, at 13:20:34
Here is the source you asked about:
http://www.calciuminfo.com/prof/3_8.htm#1
" Since 20-40% of recurrent stones are associated with elevated urinary calcium, it has been thought that consumption of high levels of calcium might cause or contribute to stone formation. In the past, it was not uncommon for patients with renal stones who also have hypercalciuria to have their intake of calcium sharply restricted. Medical science has shown, however, that stones can be prevented successfully without restricting calcium intake, provided that a number of other measures are also followed. Moreover, there is some evidence that calcium restriction may actually increase the risk of kidney stones under certain conditions.
"Calcium Intake and Stone Prevention"The largest prospective trial ever published on calcium and kidney stones, (New England Journal of Medicine,1993), concluded that high calcium intake decreases the risk of symptomatic kidney stones.1 Perhaps just as importantly, the study, conducted among over 45,000 men, found that those individuals consuming less than 850 mg of calcium per day had a higher incidence of kidney stones.
"The authors concluded that calcium may actually have a protective effect by binding to oxalate in the gut and preventing its absorption in a form that leads to kidney stones. Calcium restriction led to an increase in absorption and excretion of oxalate in the urine in both normal subjects and patients with kidney stones. The authors, as well as many previous investigators, have also concluded that urinary oxalate appears to be more important than urinary calcium in the formation of stones.
"This conclusion was supported by a subsequent study on long-term calcium supplementation in premenopausal women which found no increase in stone formation.2 Calcium supplementation lowered both urinary oxalate and urinary phosphorous (also thought to contribute to the formation of stones) by binding both agents in the intestine...............
"Calcium Intake and Kidney Stones: Risk Benefit
"While the NIH Consensus Development Conference on Optimal Calcium Intake cautioned those patients with a history of kidney stones and high urinary calcium about increasing their calcium intake excessively, the report also cited the large study showing a protective effect of higher calcium intake against kidney stones8.
"Most recently, Drs. Curhan et al, authors of the 1993 prospective study, published further data on calcium intake and stones.9 In this latest study, the authors conducted an analysis among women participating in the Nurses Health Study over a 12-year period who had no prior history of kidney stones. They found that higher dietary calcium intake was correlated with fewer kidney stones.
"Although those subjects taking calcium supplements had a slightly higher risk of stones, the incidence was only 1 case of stones per 1,000 person years. The authors propose that since 67% of women taking calcium supplements took them between meals or with breakfast, a meal usually low in oxalate, the calcium could not perform its role of blocking oxalate stone formation the same way that calcium at meals is able to do.
"In a recently completed trial, only two cases of kidney stones were reported in 2,295 women taking 2,000 mg of supplemental calcium carbonate per day.10 These results indicate that reduction of calcium intake is not advisable as a way to reduce kidney stone risk, particularly given the other benefits of adequate calcium intake, and that supplemental calcium may reduce kidney stone risk if taken with meals."
poster:noa
thread:222998
URL: http://www.dr-bob.org/babble/20030429/msgs/223718.html