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Thoughts on atrial fibrillation study

Posted on: November 18, 2011   by  Brant Cebulla


Much ado has been made over the news story “Vitamin D warning: Too much can harm your heart” that appeared on MSNBC recently. As of today, 2000 people forwarded this story over email, while 1500 shared over Facebook, and who knows how many read over it in their Google News feed or MSN check in.

The story covered a presentation at the American Heart Association annual meeting. The abstract to the presentation can be found here:

Smith MB et al. Vitamin D Excess Is Significantly Associated with Risk of Atrial Fibrillation. American Heart Assocation 2011 Meeting. 2011; 124: A14699.

The investigators found in an observational study of 132,000 subjects at Intermountain Medical Center that patients with 25(OH)D serum levels greater than 100 ng/ml were at a 2.5 times greater risk of developing atrial fibrillation. They found no increased risk of developing atrial fibrillation in levels of 0-20 ng/ml, 21-40 ng/ml, 61-80 ng/ml or 81-100 ng/ml. They did find an increased risk of hypertension, heart failure, diabetes, and renal failure for those who were deficient (0-20 ng/ml).

First off, I would like to remind everyone that levels above 100 ng/ml are hard to achieve. This is well outside levels recommend by the Endocrine Society (40-60 ng/ml), Professor Heaney (48-60 ng/ml) and the Vitamin D Council (50-80 ng/ml). Also keep in mind that we know from many studies that the higher your blood levels, the more difficult it is to raise your blood levels. In other words, 1,000 IU/day increase at a baseline 25(OH)D level of 10 ng/ml will take you much further than a 1,000 IU/day increase at a baseline level of 60 ng/ml.

A 25(OH)D level of 100 ng/ml is usually achieved with intake of 10,000 IU/day or more, coupled with consistent sun exposure. As many people with absorption issues know, even then, there is still a possibility that you do not achieve vitamin D blood serum levels greater than 100 ng/ml. This is why the Vitamin D Council recommends that anyone dosing at or higher than 10,000 IU/day get their 25(OH)D tested on a regular basis to ensure they are achieving optimal levels. Regardless of this study, we feel it is important to follow the recommendations of experts, and maintain levels between 40-80 ng/ml (either following the Endocrine Society or Vitamin D Council guidelines).

The mechanism has yet to be accounted for by the investigators of the study. And many have cited that association does not necessarily translate to causation, and in consequence, we can’t take this study too seriously. However, I would like to remind everyone that to date, 25(OH)D levels recommend by experts are largely based on observational studies and human physiology, with a strong emphasis of logic placed on what levels humans evolved to maintain in response to consistent year-round full body sun exposure. To date, there are not many randomized controlled trials that even attempt to delve into the 40-80 ng/ml range, or even open studies that attempt this.

If diseases are associated with what is presumed to be deficient levels (under 40 ng/ml, based on human physiology), then it is not unreasonable to think that there are a host of diseases associated with high levels (over 100 ng/ml, perhaps lower). With this in mind, this observational study on atrial fibrillation should not come shocking or alarming. As mentioned, it is very difficult to find subjects over 100 ng/ml, so these kinds of observational studies will not come nearly as quickly as studies observing deficient subjects.

What is unfortunate here is the lack of perspective in the MSNBC article. This study is a victim of poor journalism. The title reads like a siren, warning all who take vitamin D to stop. Much to our dismay, we are sure they achieved this for a portion of readers. They also cite a figure of 600 IU recommended daily allowance, which is irrelevant to the study. People can take several thousand units higher than 600 IU of vitamin D , and not come close to 25(OH)D levels of 100 ng/ml. The Vitamin D Council recommends 5,000 IU/day for those who do not get consistent full body sun exposure. Also note the cringe inducing typo in both the MSNBC article and the abstract. It should read “ng/ml,” not “ng/dl.” We have confirmed this error with the investigators.

Lastly, we commend the approach of Intermountain Medical Center. Says one of the investigators and staff members of the IMC, Dr. Jared Bunch,

“There are definite risks with under supplementation, so we advocate serum assessment after stable dosing in our practice.”

Dr. Bunch recommends levels between 40-80 ng/ml, right in line with what we believe in.

8 Responses to Thoughts on atrial fibrillation study

  1. Ian

    My father in law was recently hospitalised with high potassium level, dehydration and diarrhea. He is 83 and was not eating anything and probably not drinking enough. He is on aspirin, an anticoagulant and a statin, having suffered an ischaemic stroke five years ago. They stabilised his elecrolytes and discharged him. One week later he was back in hospital. My wife and I made the trip to visit him in hospital and I asked the registrar (physician) if his vitamin d levels had been tested. Of course the answer was “no”. I told him that this 83 year old spent every day inside. He would get less than 1 hour of sunshine exposure per week. So would it not be wise to test him or just medicate him with vitamin D. He couldn’t see the relevance. When He comes home again I will give him a bottle of 1000iu caps and tell him take 3 in the morning and 2 at night. I will let you know the result in a few weeks. I doubt he will get a test though!

  2. Angelo Kostas

    Who promoted the A. Fib. news article ? …Possibly the IOM. Obviously, I am being sarcastic with the aforementioned. After reading, The “Vitamin D warning: Too much can harm your heart”, it is plain to see the article is biased, and poorly written. Stating readings of 25hydroxyVitD.3 over 100 ng/ml may be harmful is redundant , and mostly insulting…in every sense of the word. To put it another way, I am not aware of any healthcare practitioner who recommends, and or promotes for 25hydroxyvitD3 levels to be over 100 ng/ml for normal, healthy individuals.

  3. James

    I don’t see this as an attack on D. More isn’t better. We’ve known D (like anything) can be poisonous for a long time. In a positive sense, they proved D up to 100 ng/ml is safe and that 100 ng/ml.

    “AF was diagnosed in 1.7%, 1.4%, 1.4%, 1.7%, 0.8%, and 3.8% …”

    There are several things we don’t know.

    Don’t know the number of people in each group.

    Don’t know the 25OHD distribution in the over 100 ng/ml group. If the 6th group range was 101-200 with a group mean of 175, might you see the findings differently?

    Don’t know their other micronutrient levels. Low magnesium, for example, might cause AF.

    We know from other research that vit D intoxication appears around 150 ng/ml. Usually that is a probability statement, so that means there is some individual variability.



    We also know that some folks like lifeguards typically have 25OHD around 100+ ng/ml at summer’s end with no problems.

    I realize this is bad math, but the average AF across the 6 groups was 1.8%. Across the first 5 was 1.4%. So, AF dx increased by 2-2.4% in the 6th group. If the >100 ng/ml sample was 291, that’s 6-7 people. The total AF dx was in theory 2,376.

    6-7 people in a group of 2,376. Holy cow, Batman!

    AF is as much as 5% amongst older folks >80.

    So, is this the end of the world? Is the sky falling? Are people dropping like flies?

    You’ll note the lowest AF rate was the 80-100 ng/ml.

    Given how difficult it is to get your serum D above 100 ng/ml, and how few folks are that high, and the small impact, I’m not quite ready to barricade my doors and prepare for a zombie attack. Of course, too much of anything is bad (love, sex, water, or D).

  4. [email protected]

    Here is my take on the Afib and >100 vitamin D. Basically the study found “3.8%” of hospitalized people with >100 ng/dL of D developed Afib, compared to a little less than 2% at the other levels who had Afib.
    Think about it, though. Levels of >100 ng/dL are rare in the general public and even more rare in (ill, often elderly) hospital patients. My guess is that they had 26 individuals (out of the 132,000 hospital patients they studied) who for some reasons had levels >100. (They combined every level higher than 100 into the same group.) If one of them developed aFib, that would account for their figure of 3.8%. That one individual might have been experiencing hypercalcemia.
    Vitamin D toxicity (hypervitaminosis D) induces abnormally high serum calcium levels (hypercalcemia), which could result in bone loss, kidney stones, and calcification of organs like the heart and kidneys if untreated over a long period of time. Hypercalcemia has been observed following daily doses of greater than 50,000 IU of vitamin D.
    In the majority of patients with hypercalcemia, the signs and symptoms are minimal. In general, the symptoms increase with higher levels of calcium in the blood. In severe cases, the elevated calcium levels can cause abnormal heart rhythms
    Too much calcium inside your body can cause problems for your heart. How your heart beats relies on a balance of calcium, a positively charged ion. Too much calcium can cause an imbalance that produces an arrhythmia. You risk suffering from atrial or ventricular fibrillation. Atrial fibrillation occurs when your atrium contracts quickly and randomly. This can cause poor blood flow, but is treatable. Ventricular fibrillation occurs when the ventricles beat rapidly and without rhythm. This is more dangerous because the ventricles supply the body directly with blood. Ventricular fibrillation can result in sudden death.
    (that last paragraph is from: http://www.livestrong.com/article/529421-what-is-the-result-of-too-much-calcium-in-the-human-body/#ixzz1e7tyMC8L )
    (And oh, by the way, the study mentions that low vitamin D was associated with higher hypertension, heart failure, diabetes, and renal failure.)

  5. James

    Life Extension:

    “The data corroborates what was previously published showing that those with higher vitamin D blood levels have substantially lower risks of degenerative disease. For example, those whose 25-hydroxyvitamin D level ranged from 61–80 ng/mL had a 52% reduction in diabetes risk compared to those with deficient levels (below 20 ng/mL).1

    Those whose 25-hydroxyvitamin D levels ranged 81–100 ng/mL had a 36% reduction in hypertension incidence when measured against the deficient group. Compared to people in the deficient range, those with higher blood levels of 25-hydroxyvitamin D had significantly lower risk of heart failure, depression, coronary artery disease, kidney failure and prior stroke.1”

    “As the population ages, an increasing percentage develops an irregular rhythm in the upper chambers of the heart called atrial fibrillation. It is the most common type of heart arrhythmia and approximately 5% of persons over 65 years of age are expected to be diagnosed with it.2”

    “It is interesting to note that in patients with excess amounts (greater than 100 ng/mL) of 25-hydroxyvitamin D in the study presented at the American Heart Association conference, a significant increase in hypothyroidism (sluggish thyroid function) was noted by the researchers. While hyperthyroidism (hyperactive thyroid function) is a well-known contributing factor in atrial fibrillation, in fact hypothyroidism is an underappreciated cause of heart disease, high cholesterol, and atrial fibrillation. The high prevalence of hypothyroidism in those with excess 25-hydroxyvitamin D represents an underappreciated risk factor for atrial fibrillation in this observational trial. In other words, it may have been hypothyroidism that caused the increased incidence of atrial fibrillation and not the vitamin D.5-7 “

  6. Donna

    On the meeting abstract from Circulation publication, the 25OHD measurement is reported as ng/dL which is an odd measurement to use, and does not give me confidence in the research design or analysis. The reports were lacking in detail about the number of patients in each group and about the actual numbers affected by atrial fibrillation. It does not seem valid. Very unfortunate that this will confuse many people.
    “25[OH] Vit D levels were determined by the hospital laboratory and were grouped into the following categories (ng/dL): 100: n=291 (0.2%). Multivariable Cox hazard regression analysis (mean length of follow-up: 584.4±494.7 days) was used to evaluate 25[OH] Vit D categories for incident AF (determined by ICD-9 codes). “

  7. [email protected]

    Wonderful article and comments!

    I am a 57 years old, one-half Cherokee Indain woman dx with RA (25 years) FMS (25 years), Neuropathy both feet (10 years), Osteoporosis, (this past year when I had a compression fracture at T4 from a cough), A Fib (dx March 2011). On 2 heart meds for A fib and withdrawing 15mg prednisone. RA doc wanted me on the bone pharma, but I said no!

    I wish I knew about the low Vitamin D years ago. I think I would have been saved much disability and pain.

    Last year I had first Vitamin D level checked it was 23! The doctor did the 50.000iu protocol they use. I found out about this site and changed.

    I took 5000iu (Source Naturals caps) a day. My levels got up in the 60’s. Docotor asked me to back off I did, they dropped to the high 30’s and I felt more ill. This time I told the doctor I will do this with the 500iu 5 days a week. I want to get it close to 80’s and hold it there. She did not want me to, but I told her we will keep eye on it.

    When I ordered my Vit D3 from the site I use, all they had was 2000iu caps so now I take 4-2000iu a day for 5 days.

    I had levels checked 2 weeks ago now it is at 69! I will keep doing this and being checkied every 3 months.

    In March of this year suddenly I had A Fib. My numbers were not close to 80’s. Before beginning Vitamin D3 supps I have nodules on my thyroid they are watching. I was hoping these may disappear. I think the A fib has something to do with this. My Thyroid levels are in the low normal level. I told my doc maybe that low is to low for me.

    A few months ago I had a higher calcium level for one blood work. Doc talk about the parathyroid glands not funtioning properly. Our calcium should never be high, if it is this gland is involved I have read.

    Just wanted to add what I am experiencing.

  8. markcrouch

    The study found that AF was diagnosed in 1.7%, 1.4%, 1.4%, 1.7%, 0.8%, and 3.8% for the Vitamin D blood level groups of 0-20, 21-40, 41-60, 61-80, 81-100, and >100 ng/ml. This clearly indicates that the lowest AF group was the group with Vitamin D levels of 81-100 ng/ml with about half the risk compared to all the other groups except the >100 group. So, everyone should strive for Vitamin D levels between 81-100 ng/ml for the lowest risk, Right? That is what this study says.

    This is an example of a poor study design. Every blood level group measured in increments of 20 mg/ml except the last group of >100. What was the average Vitamin D level in this group, 200, 250, 300,…? If the 81-100 ng/ml group had the lowest risk, it may very well be that the 101-120 ng/ml group had an even lower risk than that! This study tells us nothing. It is like saying fasting blood sugar levels over 85 cause kidney damage and blindness while studying a group of people with an average FBS of 400. I smell a rat!

    My theory is that over supplementation with Vitamin D will cause the Magnesium levels to drop. Magnesium is an important cofactor for Vitamin D function and Vitamin D uses up Magnesium. Low Magnesium increases the risk for most arrythmias and sudden cardiac death. Vitamin D levels high enough to cause toxicity will also cause hypercalcemia which is not too good for people prone to arrythmias either. This study does not really tell us at what Vitamin D levels the risk for A-fib is increased.

    The only real thing this study shows is that hospitalized patients with Vitamin D levels between 81-100 ng/ml are at the lowest risk for A-fib than any of the groups. Otherwise this study only begs the following questions:
    1. What were the patients magnesium and calcium levels in the >100 ng/ml group?
    2. What was the average Vitamin D level in the >100 ng/ml group?
    3. How many total patients were in the >100 ng.ml group?
    4. How many patients had blood levels of 101-120, 121-140, 141-160, 161-180, 181-200, and 201-220 ng/nl and how many in each group were diagnosed with A-fib?
    5. What were the patients hospitalized for in the >100 mng/ml group?
    6. What was the A-fib rate in the 101-120 ng/ml group?
    7. Should everyone who is at risk for A-fib strive for blood levels of 81-100 ng/ml?
    8. Is there anyone peer reviewing these articles before they are being published?
    9. Were the patients with A-fib. taking Vitamin D2 or Vitamin D3?
    10. What method was used to assess the Vitamin D levels: Mass Spectrometry or Chemiluminescent Immunoassy?
    11. How reliable is the lab doing the testing? Was it Clinical Pathology Laboratory, Mayo Clinic, LabCorp, etc.?

    There are so many questions and so few answers found in this study. Until a better study is done, keep taking your vitamin D. Don’t forget the magnesium so the vitamin D can function. And finally, be careful with those fasting blood sugars above 85.

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