Can Too Much Vitamin D Harm Cardiovascular Health? Probably
Editor's ChoiceAcademic Journal
Main Category: Cardiovascular / Cardiology
Also Included In: Nutrition / Diet
Article Date: 09 Jan 2012 - 7:00 PST
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Although vitamin D has long been known to promote bone health and protect the heart, researchers at John Hopkins reveal that vitamin D might stop conferring cardiovascular benefits and may cause harm as blood levels increase above what is considered normal.
According to Muhammad Amer, M.D., study leader and assistant professor in the division of general internal medicine at the John Hopkins University School of Medicine, findings from the investigation demonstrate that rising vitamin D levels in the blood are associated with decreased levels of c-reactive protein (CRP: a popular marker for cardiovascular inflammation).
Together with Rehan Qayyum, M.D., M.H.S., an assistant professor in the division of general internal medicine at Hopkins, Amer analyzed data in the continuous National Health and Nutrition Examination Survey, a nationally representative sample, of over 15,000 adult participants from 2001 and 2006. In adults without cardiovascular symptoms but with fairly low levels of vitamin D, Amer and Qayyum discovered a different association between vitamin D and CRP, a factor associated with stiffening of the blood vessels and an increased risk of cardiovascular problems.
They found that individuals with close to normal vitamin D levels had lower levels of inflammation. Any additional increase in vitamin D in blood levels of 21 nanograms per milliliter of 25-Hydroxyvitamin D - considered the low end of the normal range for vitamin D - was connected with an increased risk of developing CRP.
Amer, whose latest discoveries can be found in the January 15 issue of the American Journal of Cardiology, explained:
"The inflammation that was curtailed by vitamin D does not appear to be curtailed at higher levels of vitamin D.
Clearly vitamin D is important for your heart health, especially if you have low blood levels of vitamin D. It reduces cardiovascular inflammation and atherosclerosis, and may reduce mortality, but it appears that at some point it can be too much of a good thing."
Physicians should know about the potential risks of vitamin D supplements and consumers should be cautious before taking them. Every 100 international units of vitamin D consumed daily generate approximately one nanogram per milliliter increase 25-Hydroxyvitamin D levels in the blood.
Amer said:
"People taking vitamin D supplements need to be sure the supplements are necessary. Those pills could have unforeseen consequences to health even if they are not technically toxic."
According to Amer and Qayyum, the molecular and biological mechanisms responsible for the loss of cardiovascular benefit are not clear.
The primary source of vitamin D is the sun. Although commercially sold milk usually contains vitamin D, very few foods contain this nutrient. Concerns are increasing that several individuals are deficient in vitamin D, as people spend more time indoors and protect their bodies with sunscreen.
Amer says:
"As a result many doctors prescribe vitamin D supplements, and many consumers, after reading news stories about the vitamin's benefits, dose themselves. Older women often take large doses to fight and prevent osteoporosis."
Written by Grace Rattue
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today
MLA
23 Feb. 2012. <http://www.medicalnewstoday.com/articles/240070.php>
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http://www.medicalnewstoday.com/articles/240070.php.
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Visitor Opinions In Chronological Order (9)
Do not forget to check vit D
posted by sylvia on 9 Jan 2012 at 9:37 amCaught my attention this article, we do not forget to check vit D in the next check-up
Too much D?
posted by rocketmouse on 9 Jan 2012 at 11:41 amI am one of those "Older women." I was taking a D supplement at 400mg/day when I read (on the Internet) that if you don't get out in the sun much you should take more, so the next time I bought D I got (what I thought was) a bigger dose/day. But, the new bottle states the contents in IU (5000/softgel.) How do you compare mg and IU, and how do you know when you're getting too much?
Menaquinone - organ meats
posted by Anna Wilde on 9 Jan 2012 at 1:30 pmVitamin D needs to be balance with other nutrients such as vitamin k, (menaquinone) and vitamin A. Hence the purpose of eating it as a whole food in organ meats and fish, and not taking it as a supplement!
Causal link is unlikely
posted by Count Iblis on 9 Jan 2012 at 5:00 pmOnly a double blind study where you give participants a placebo or a high dose vitamin D supplement (and where exposure to the midday Sun is limited), can prove a causal link between vitamin D intake and health. Studies where one correlates calcidiol levels with some aspect of physical health, cannot rule out other effects that can explain the correlation, unless we already know that vitamin D is involved here.
In this case, a priori, one would not have strong reasons to believe that vitamin D has an important role to play in cardiovascular inflammation. Also before 2008, few people took high dose vitamin D supplements. From the diet you can only get small amounts of vitamin D, your calcidiol level will then not rise above below 20 ng/ml, while regular Sun exposure will typically get you to significantly higher values (without using supplements). Then given that 21 ng/ml is actually considered to be not just on the low end of normal but flat out deficient by many experts, one should seriously consider the diet as an alternative hypthesis that could explain the result.
One possibility is a link with consumption of fatty fish. Fatty fish contains much more vitamin D than other food sources, you can get up to 800 IU by eating fish. People who don't get much exposure to the Sun, but who eat a lot of fatty fish will have calcidiol levels that are significantly higher than people with similar low Sun exposure. So, within this group of people who will typically have calcidiol levels of below 20 ng/ml, you would expect a correlation with consumption of fish. But the effect on cardiovascular inflammation may be due to Omega 3 fats, instead of the vitamin D.
Then, in the people who do get regular exposure to the Sun, the huge amount of vitamin D they get from that (thoudsands on IU's per day) completely wipes out the signal from the fish in the diet. Also the higher your calcidiol level is the less it goes uop with an additional intake of vitamin D. The rule of thumb mentioned in the article: "Every 100 international units of vitamin D consumed daily generate approximately one nanogram per milliliter increase 25-Hydroxyvitamin D levels in the blood.", only works for calcidiol levels below 20 ng/ml, if your calcidiol level is 80 ng/ml, it is approximately half a ng/ml increase per 100 IU/day consumed more.
This means that in the high calcidiol level group, you would expect to see the average CRP, but because at the high end of the people with low levels, the CRP is lower than average, you will see that the level goes up when the calcidiol level rises above 21 ng/ml.
Reply To Rocketmouse
posted by Count Iblis on 10 Jan 2012 at 6:43 am100 IU equals 2.5 micrograms. So, 5000 IU is 125 micrograms.
Taking up to 10,000 IU/day is safe, although people suffering from certain illnesses should only take vitamin D under strict monitoring of their blood calcium levels. However, even for these people the risk of getting ill from doses below 10,000 IU/day is quite low. You can find a detailed analysis about this issue here:
http://www.ajcn.org/content/85/1/6.full
Thank You
posted by rocketmouse on 10 Jan 2012 at 7:45 amThank you, Count Iblis.
Your thoughtful answer was easier to "digest" than the (linked to) article itself.
CRP caused inflammation a possibility, not probability
posted by Auburn on 10 Jan 2012 at 8:14 amThe Amer study showed only an “association”, not “causation”, between the CRP level and vitamin D level. It did not study heart disease. A study done at the Imperial College London and published (2009) in the Journal of the American Medical Association found that high levels of C-reactive protein (CRP) in the blood probably don't cause hardening of the arteries or heart disease. Please distinguish between fact and opinion.
Vitamin D generally safe; most people are very deficient
posted by Milton Hare on 10 Jan 2012 at 6:32 pmThe "normal" level of Vitamin D3 reported, 20 ng/ml, is below normal according to Kaiser HMO which has established a "normal" range of 30-100 ng/ml. The body does not begin to actively store extra Vitamin D3 until levels reach around 50 ng/ml, according to Reinhold Vieth, MD, a respected epidemiologist who studies Vitamin D3. It takes a dose of around 5,000 iu daily to reach this level. Individuals vary in how well they utilize supplements or sunshine, the two main sources of D3, and the gold standard test is the 25(OH)D serum (blood) test for D3 (cholecalciferol). The article references a study that associated fairly high doses of Vitamin D3 with a higher pulse, and that study only hypothesized that a higher pulse might mean damage to the heart, or, might precipitate a heart event of some kind. Recently there have been a few high profile articles about Vitamin D3 that are negative; there are literally thousands of research articles shedding light on the importance of Vitamin D3 to overall health. Vitamin D3 appears to regulate your immune system, reducing auto-immune symptoms like high blood pressure and high blood sugar, and, has an impact on cancer, including noncontroversial findings in relation to colon and breast cancer. There is nothing wrong with taking 4,000 iu of Vitamin D3 daily, according to the US National Institute of Health; in fact, Reinhold Vieth, respected researcher, has suggested that 10,000 iu per day is a safe dose, based on a review of studies that found no adverse effects from 40,000 iu per day. Studies like the one referenced in this article are likely sponsored at least in part by the pharmaceutical industry which does not benefit from competition with a cheap and effective medicine like Vitamin D3 that anyone can buy from almost any store, without a prescription.
Dr John Cannell MD Responds
posted by Peter on 24 Jan 2012 at 7:46 pmDr John Cannell MD of the Vitamin D Council has responded specifically to the paper discussed in your article. You can find his response in The Health Gazette here:
http://the-health-gazette.com/1301/response-to-crp-and-vitamin-d-association-finding/
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