This transcript has been edited for clarity.
Tricia neighborhood: Hi. My name is Tricia Ward, from theheart.org | Medscape Cardiology. I’m joined today by Dr. Matthew Budoff. He is a professor of medicine at UCLA and chair of preventive cardiology at the Lundquist Institute. Welcome, Dr. Budoff.
Matthew J. Budoff, MD: THANKS.
Dietary calcium vs. coronary calcium
Room: The reason I wanted to talk to you today is because recent studies have linked calcium supplements to an increased risk of cardiovascular disease. I’m old enough to remember when we told people that dietary calcium and coronary artery calcium were not related and were not the same. Are we wrong?
Budoff: I think there is still a lot of mixed data. The U.S. Preventive Services Task Force looked into the issue several years ago and said there was no link between calcium supplementation and an increased risk of cardiovascular disease.
As you mentioned, a few more recent studies point us toward a relationship. I think we’re still a little mixed up, but we need to dive into it a little deeper to understand what’s going on.
Room: Does this seem to be related to calcium in supplement form versus calcium from food?
Budoff: We looked very carefully at dietary calcium in the MESA study, the Multi-Ethnic Study of Atherosclerosis. There is no relationship between dietary calcium intake and coronary or cardiovascular events. We’re mostly talking about supplements now when we talk about this increased risk that we’re seeing.
Room: Because this is seen with supplements, is it likely because the concentration of calcium is much higher or do you think it is something inherent in the fact that it comes in supplement form ?
Does vitamin D exacerbate risk?
Budoff: I think there are two things. First, 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 were drinking a calcium-rich food or drink.
Additionally, most supplements also contain vitamin D. I believe that vitamin D and calcium work synergistically. When you administer them both simultaneously, I think it may have a more potentiating effect that could exacerbate any potential risks.
Room: Is there any reason to think there might be a difference in the type of calcium supplement? I always think about the chalky tablet form versus the calcium chews.
Budoff: I don’t know of any difference in the type of supplement. 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 very high numbers and it stays in the system.
Personally, I think part of the explanation is that with very high levels of vitamin D in addition to calcium supplementation, you now absorb it better. You are now introducing it into the bones, but perhaps also into the coronary arteries. If you are very high in vitamin D and then take a large calcium supplement, it may be the calcium/vitamin D combination that is causing us problems. I think people taking vitamin D supplements really need to monitor their levels and not resort to supratherapeutic therapies.
Room: With vitamin D?
Budoff: With vitamin D.
Diabetes and kidney function
Room: In some studies, there appears to be a higher risk in diabetic patients. Is there any reason why this would be the case?
Budoff: I don’t exactly see why with diabetes per se, other than kidney disease. Diabetic patients have more intrinsic kidney disease, proteinuria, and even reduced eGFR. We have seen that the kidney is very strongly linked to this. We have a very strong relationship, in work I did ten years ago now, showing that calcium supplementation (in the form of phosphate binders) in patients on dialysis or with advanced kidney disease is linked to a much higher progression of coronary calcium.
We conducted prospective randomized trials showing that providing calcium as a binder to reduce phosphorus resulted in increased coronary calcium. We always thought that this was just relegated to the kidney population, and that there might be some overlap here with diabetes and other kidney diseases. I have a feeling it has to do with more of that. It could also be a regulation of parathyroid hormone, which could be more abnormal in diabetic patients.
Avoid supratherapeutic levels of vitamin D
Room: What do you tell your patients?
Budoff: I tell patients with normal kidney function that bone will modulate 99.9% of calcium absorption. If they have osteopenia or osteoporosis, regardless of their calcium score, I’m very comfortable giving them supplements.
I’m a little more careful with vitamin D levels, monitoring that and regulating the amount of vitamin D they get based on their levels. I bring them back into the normal range, but I don’t want them to be supratherapeutic. You can even track their calcium score. Again, we have demonstrated that if you take too much calcium, your calcium score will increase. I might just check it again in a few years to make sure it’s safe.
Room: In terms of vitamin D levels, when you say “supratherapeutic”, what levels do you consider a safe amount to take?
Budoff: I would like them below 100 ng/mL up to their higher level. Normal is around 70 ng/mL in most laboratories. I try to keep them within the normal range. I don’t even want them to be normal if I have to give them calcium supplements at the same time. Of course, if they have kidney failure, I’m much more careful. We have even seen calcium supplements increase serum calcium, something you never see with dietary calcium. This is further potential evidence that it might be too much, too soon.
For kidney patients, even in mild kidney failure, maybe even in diabetes where we saw a signal, maybe aim for lower calcium supplementation if the diet is insufficient, and aim for a little lower the vitamin D goals, and I think you’ll be in a safer place.
Room: Is there anything else you would like to add?
Budoff: The evidence is still evolving. I would say it’s interesting and maybe a little frustrating that we don’t have a definitive answer to any of this. I’ll stay tuned for more data, because we’re looking at a lot of epidemiological studies to try to see what’s happening in the real world, both with dietary calcium intake and with calcium supplementation.
Room: Thank you very much for joining me today.
Budoff: It’s a pleasure. Thank you for.