Not too long ago, a patient of mine came in for her annual  Bio-Energy Test. When I went over her supplement program, she told me that she  had cut her dose of vitamin D in half.
I was surprised because I had carefully adjusted her dose so  that her blood vitamin D levels were above 65 ng/ml. This is the level that all  the studies suggest is the most optimum for disease prevention.
She said another doctor had told her that taking vitamin D3  was dangerous, and that she did not need as much as she was taking. That’s why  she cut the dose.
So I checked her blood level to see how the new dose was  doing.
The result: Not so good. Her blood level was down to 25  ng/ml — much lower than optimum.
We already know that by lowering her vitamin D3 level, the  doctor may have been placing this patient at greater risk for diabetes, cancer,  osteoporosis, infectious disease, and autoimmune disease.
Many studies show that low vitamin D levels can cause all of  these problems. But that’s not all he did. A new study says he also increased  her risk of having a heart attack.
In their study, researchers at the University of Missouri in  Kansas City found that, “Deficiency in 25-hydroxyvitamin D [vitamin D3] is a  treatable condition that has been associated with coronary artery disease and  many of its risk factors.”
As a result, they wanted to see if this translated into  actual heart attacks. So they looked at the blood levels of vitamin D in 239  people who were admitted to the hospital with a heart attack.
Out of that group, they found that 96% of them had  abnormally low levels. Let me put that into perspective for you.
The reference ranges for vitamin D3 go from a low of 30  ng/ml to a high of 100 ng/ml. This means that statistically speaking, only 2%  of the general healthy population will fall below 30.
However, in this group of patients having just had a heart  attack, 96% had levels below 30. That means that patients having a heart attack  are 48 times more likely to have low levels of vitamin D3 than their healthy  colleagues. That is a remarkable statistic! And one that should motivate  everyone to take enough vitamin D3 to get their levels up in the healthy range.
I can't imagine why any doctor would tell a patient that  taking a vitamin D supplement that keeps their blood levels in the higher end  of the reference range is dangerous.
There is no evidence at all for such a statement. And, in  fact, by acting on this erroneous belief, this doctor is putting her patients  at greater risk not only for the diseases mentioned above, but also for heart  attacks.
Most people need to take 5,000 IU or more to stay above 65  ng/ml. Remember, that’s the optimum level required to prevent heart attacks and  other diseases. So make sure you’re taking at least 5,000 IU daily.
Sources: 
Lee JH, Gadi R, Spertus JA, Tang F, O'Keefe JH.  Prevalence of vitamin D deficiency in patients with acute myocardial  infarction. Am J Cardiol. 2011 Jun 1;107(11):1636-8. Epub 2011 Mar 23.