Professor Margaret Pearle calcium and Kidney Stones Interview

Professor Margaret Pearle calcium and Kidney Stones Interview

Question: Can you talk about the role of calcium in developing kidney stones?

Professor Margaret Pearle: There is a large study that came out from Women's Health Initiatives that looked at over 36,000 women without a history of Kidney Stones who were randomised to receive calcium and vitamin D supplements or a placebo. The study followed the women over time and the reason they did the study was to see if there was a reduction in risk of hip fractures but as a secondary point they queried these women about whether or not they formed Kidney Stones during the course of the study; they found there was a 17% higher incident of Kidney Stones in the group that was taking calcium and vitamin D supplements. There is some concern that calcium and vitamin D supplements could potentially increase the risk of Kidney Stones.

Although this isn't a new study some of these women were taking pretty high doses of calcium and some of the women were already on calcium supplements and they didn't require that they stop taking those supplements. They were given 1,000mg of calcium and 400IU of vitamin D so some of the women were taking far in excess of the daily allowance of calcium.

What we don't know is that if women are taking the recommended amount of calcium if they would have an increased risk as the study didn't look at that. What they did find is that when women were supplemented with 1,000mg of calcium on top of what they were already getting that there was an increased risk of Kidney Stones.


Question: Is this only dietary calcium supplements or calcium found in food and drinks?

Professor Margaret Pearle: We are talking about calcium supplements however they didn't specify how much calcium they should take in their diet and there was a lot of variability in that. There were about two thirds of women that were taking 800mg or more of calcium already, just in their diet but then once you added the 1,000mg of calcium to it than they were on extremely high doses.

There is some concern that calcium supplements could potentially increase the risk of Kidney Stones and I'm not saying people shouldn't take calcium supplements as we don't want women to have an inadequate calcium intake; we do want them taking their recommended daily allowance for calcium as we want to protect their bones. I do not want to make any recommendations that would jeopardise bone density in post-menopausal women however it is something we do need to have some concerns about.


Question: Why are many women taking dietary calcium supplements?

Professor Margaret Pearle: I believe there are a lot of women who don't get their adequate daily allowance for calcium as they don't take a lot of dairy. My biggest concern isn't your average woman who has never had a Kidney Stone, I am more worried about the people that have or had Kidney Stones. The bottom line is that we don't want to compromise their bone mineral density but we also don't want to be overly supplementing them either; women should take the amount they need so they don't compromise their bone mineral density but not necessarily more because there isn't evidence to prove that it improves their bone density or reduces the rate of fracture in fact in this particular study it didn't reduce the rate of fracture.


Question: How much calcium do we need for our bone density?

Professor Margaret Pearle: In pre-menopausal women the recommended daily allowance for calcium is 1,000mg a day. In post-menopausal women the recommended daily allowance for calcium is 1,200mg a day.

It is important women get their recommended daily allowance for calcium and to get it from their diet. Many women don't get enough calcium and do need to be on a supplement however I would assume they would take it as food in their diet rather than a supplement.


Question: What are Kidney Stones?

Professor Margaret Pearle: Kidney Stones are concretions; crystals that form and aggregate and they are primarily made of calcium in 80% of cases although there are Kidney Stones that have other compositions.


Question: Is there a treatment for kidney stones?

Professor Margaret Pearle: Not all Kidney Stones have to be treated. Kidney Stones that are in the kidney that aren't causing any obstruction to the outflow of urine don't require any treatment at all, necessarily. Kidney Stones that do move out of the kidney and start to travel down the tube that connects the kidney to the bladder, those stones can cause blockages and that's what we describe as -passing a stone acutely' and they need to be seen in the emergency room; they may successfully pass on their own.

Larger Kidney Stones are less likely to pass and Kidney Stones that cause pain, stones that are growing, or stones that are causing infection need to be treated. The treatment options are almost all minimally invasive and we do almost no open surgery for Kidney Stones, anymore. The most commonly performed procedure is Extracorporeal shock wave lithotripsy (ESWL) which is a procedure in which shock waves are focused on a Kidney Stones using X-Ray and the shock waves are repeatedly fired at the stone until the stone pulverises into sand or gravel and the fragrants can be washed out of the kidney with the flow of urine.

The other treatment option generally uses Endoscopes one is using a flexible endoscope through the urethra into the bladder and up the ureter to a stone or into the kidney and then using lasers to break the stone into little pieces that we can pull out or allow the patient to pass.

The most invasive of the minimally invasive procedures is a procedure where we make a small incision in the back and pass a small tube through the back, into the kidney and we pass a telescope through that tube so we can see directly in the kidney and fragment the stones and pull the pieces out directly and we do not leave any pieces to pass at all.

These are the three most common treatment procedures however the procedure through the back is the least common of those three.


Question: If women believe they are not getting enough calcium in their diets, what should they do?

Professor Margaret Pearle: If there is some reason that a women cannot take dairy because they are allergic or don't like it a calcium supplement may be necessary. There are non-dairy sources of calcium such as spinach, almonds and soy milk. I'd suggest looking online for non-dairy sources of calcium. Most people could get an adequate amount of calcium from their diet, if they make an effort. For those who can't, calcium supplement may be necessary.
I'm not a bone expert, I treat stones but the issue is that we so often have these conflicting pieces of information and recommendations surrounding preserving bone density and health. Historically people have restricted their calcium intake when they have stones and that philosophy has been rethought to some degree but on the other hand I don't want people doing the opposite and taking high calcium intakes and potentially increase the risk of kidney stones.


Interview by Brooke Hunter