This transcript has been edited for clarity.
Tricia Ward:Hi. I'm Tricia Ward, from theheart.org | Medscape Cardiology. I'm joined today by Dr Matthew Budoff. He is professor of medicine at UCLA and the endowed chair of preventive cardiology at the Lundquist Institute. Welcome, Dr Budoff.
Matthew J. Budoff, MD:Thank you.
Dietary Calcium vs Coronary Calcium
Ward:The reason I wanted to talk to you today is because there have been some recent studies linking calcium supplements to an increased risk for cardiovascular disease. I'm old enough to remember when we used to tell people that dietary calcium and coronary calcium weren't connected and weren't the same. Were we wrong?
Budoff:I think there's a large amount of mixed data out there still. The US Preventive Services Task Force looked into this a number of years ago and said there's no association between calcium supplementation and increased risk for cardiovascular disease.
As you mentioned, there are a couple of newer studies that point us toward a relationship. I think that we still have a little bit of a mixed bag, but we need to dive a little deeper into that to figure out what's going on.
Ward:Does it appear to be connected to calcium in the form of supplements vs calcium from foods?
Budoff:We looked very carefully at dietary calcium in the MESA study, the multiethnic study of atherosclerosis. There is no relationship between dietary calcium intake and coronary calcium or cardiovascular events. We're talking mostly about supplements now when we talk about this increased risk that we're seeing.
Ward:Because it's seen with supplements, is that likely because that's a much higher concentration of calcium coming in or do you think it's something inherent in it being in the form of a supplement?
Does Vitamin D Exacerbate Risk?
Budoff:I think there are two things. One, it's definitely a higher concentration all at once. You get many more milligrams at a time when you take a supplement than if you had a high-calcium food or drink.
Also, most supplements have vitamin D as well. I think vitamin D and calcium work synergistically. When you give them both together simultaneously, I think that may have more of a potentiating effect that might exacerbate any potential risk.
Ward:Is there any reason to think there might be a difference in type of calcium supplement? I always think of the chalky tablet form vs calcium chews.
Budoff:I'm not aware of a difference in the supplement type. I think the vitamin D issue is a big problem because we all have patients who take thousands of units of vitamin D — just crazy numbers. People advocate really high numbers and that stays in the system.
Personally, I think part of the explanation is that with very high levels of vitamin D on top of calcium supplementation, you now absorb it better. You now get it into the bone, but maybe also into the coronary arteries. If you're very high in vitamin D and then are taking a large calcium supplement, it might be the calcium/vitamin D combination that's giving us some trouble. I think people on vitamin D supplements really need to watch their levels and not get supratherapeutic.
Ward:With the vitamin D?
Budoff:With the vitamin D.
Diabetes and Renal Function
Ward:In some of the studies, there seems to be a higher risk in patients with diabetes. Is there any reason why that would be?
Budoff:I can't think of a reason exactly why with diabetes per se, except for renal disease. Patients with diabetes have more intrinsic renal disease, proteinuria, and even a reduced eGFR. We've seen that the kidney is very strongly tied to this. We have a very strong relationship, in work I've done a decade ago now, showing that calcium supplementation (in the form of phosphate binders)in patients on dialysis or with advanced renal disease is linked to much higher coronary calcium progression.
We did prospective, randomized trialsshowing that calcium intake as binders to reduce phosphorus led to more coronary calcium. We always thought that was just relegated to the renal population, and there might be an overlap here with the diabetes and more renal disease. I have a feeling that it has to do with more of that. It might be regulation of parathyroid hormone as well, which might be more abnormal in patients with diabetes.
Avoid Supratherapeutic Vitamin D Levels
Ward:What are you telling your patients?
Budoff:I tell patients with normal kidney function that the bone will modulate 99.9% of the calcium uptake. If they have osteopenia or osteoporosis, regardless of their calcium score, I'm very comfortable putting them on supplements.
I'm a little more cautious with the vitamin D levels, and I keep an eye on that and regulate how much vitamin D they get based on their levels. I get them into the normal range, but I don't want them supratherapeutic. You can even follow their calcium score. Again, we've shown that if you're taking too much calcium, your calcium score will go up. I can just check it again in a couple of years to make sure that it's safe.
Ward:In terms of vitamin D levels, when you're saying "supratherapeutic," what levels do you consider a safe amount to take?
Budoff:I'd like them under 100 ng/mL as far as their upper level. Normal is around 70 ng/mL at most labs. I try to keep them in the normal range. I don't even want them to be high-normal if I'm going to be concomitantly giving them calcium supplements. Of course, if they have renal insufficiency, then I'm much more cautious. We've even seen calcium supplements raise the serum calcium, which you never see with dietary calcium. That's another potential proof that it might be too much too fast.
For renal patients, even in mild renal insufficiency, maybe even in diabetes where we've seen a signal, maybe aim lower in the amount of calcium supplementation if diet is insufficient, and aim a little lower in vitamin D targets, and I think you'll be in a safer place.
Ward:Is there anything else you want to add?
Budoff:The evidence is still evolving. I'd say that it's interesting and maybe a little frustrating that we don't have a final answer on all of this. I would stay tuned for more data because we're looking at many of the epidemiologic studies to try to see what happens in the real world, with both dietary intake of calcium and calcium supplementation.
Ward:Thank you very much for joining me today.
Budoff:It's a pleasure. Thanks for having me.
