Can You Be Damaging Your Heart with Vitamin D?

Q. Can taking a vitamin D supplement be bad for your heart?

A. The recent uproar over taking vitamin D supplements comes from a study reported in this MSNBC article [http://www.msnbc.msn.com/id/45325473/ns/health-diet_and_nutrition/t/vitamin-d-warning-too-much-can-harm-your-heart/]. What’s at the heart of this matter? On November 16^th, scientist Dr. Jared Bunch, director of electrophysiology research at the Intermountain Medical Center in Murray, Utah, presented a paper that said too much vitamin D can more than double the risk of developing atrial fibrillation, which is a potentially dangerous heart condition associated with heart failure and stroke. In this study that followed 132,000 patients, those participants with the highest vitamin D levels (above 100ng/dl) were 2.5 times more likely to develop atrial fibrillation.

This study received a lot of press because it suggests taking vitamin D supplements is dangerous. However, in Western medicine, we have known for a long time that taking too much vitamin D is not a good idea and the goal level for vitamin D in your blood should always be less than 100 ng/dl. So in effect, this study is basically saying what we already knew – that if you go above the target level of vitamin D in the blood, you are at increased risk of side effects.

That being said, it is generally quite hard to go above a serum level of 100 ng/dl of vitamin D, even if you take 2000 IU of vitamin D per day and sometimes more. In my opinion, the real issue isn’t that taking too much is bad – we already knew that - but that there is a wide range of “normal” blood levels of vitamin D, ranging from 35 ng/dl to 100 ng/dl. As a result, we still don’t know what the ideal level to target in the blood is exactly.

One answer to that question may lie in Hawaii. A small study on Hawaiian surfers suggests that under “natural” conditions – that is, when you just get your vitamin D from the sun – that the human body equilibrates to around 40 to 50ng/ml in the blood. This is the amount I currently target when I work with patients in my practice.

Another important point to keep in mind is that if you don’t get enough vitamin D, you are also at increased risk of heart disease, MS and cancer. And in places with latitudes like Seattle, it’s very difficult to receive enough vitamin D from the sun. So basically, just like many things in life, the goal is to get the right amount of vitamin D – not too much, and not too little. For this reason, I generally recommend that people get their vitamin D levels checked, and base the amount they take on their blood levels, rather than just “winging it.”