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Article Date: 06 May 2013 - 11:00 PDT Current ratings for:
Vitamin D Supplementation - Be Careful, Researchers Warn
Very high blood levels of vitamin D confer no additional benefit, researchers from Johns Hopkins reported in the American Journal of Medicine. In fact, when they combined the results of their present and previous studies, they found that raising vitamin D levels in "healthy people" with already normal levels may be potentially harmful.
Healthy people and health care professionals have been bombarded with stories from health websites and the media about the hazards of low vitamin D levels, urging people to take supplements to protect against hardening of the arteries, hypertension, diabetes, weak bones, and a range of other illnesses.
Study leader Muhammad Amer, M.D., M.H.S., said:
"Healthy people have been popping these pills, but they should not continue taking vitamin D supplements unchecked. At a certain point, more vitamin D no longer confers any survival benefit, so taking these expensive supplements is at best a waste of money."
Some people definitely do benefit from higher vitamin D blood levels and should be considered for supplements, they include: elderly womenpatients with kidney diseasepostmenopausal womenvery obese peopleIn this study, Dr. Amer and Dr. Rehan Qayyum reviewed data from over 10,000 participants in NHANES (National Health and Nutrition Examination Survey) from 2001 to 2004. They then matched the data they had gathered with those contained in the National Death Index through the end of 2006.
When they examined details on deaths from all causes and specifically cardiovascular disease, they found that people whose blood levels were at the top range of what the Institute of Medicine considers "adequate" (21 nanograms per milliliter of 25-Hydroxyvitamin D) had a 50% lower risk of dying prematurely.
However, as blood levels of vitamin D rose above 21 nanograms per milliliters, that protective effective seemed to wear off.
The main source of vitamin D is skin exposure to direct sunlight. Vitamin D can be found naturally in a small number of foods, including salmon, sardines and mackerel (oily fish). Commercially sold milk, fat spreads and some breakfast cereals are fortified with vitamin D.
Many people are starting to wonder whether they should be slapping on so much sunscreen when going outdoors if sunlight is the main source of vitamin D, Dr. Amer explained. The problem is, no set amount of supplementation can raise vitamin D levels to 21 nanograms per milliliter because we do not all process vitamins in the same way.
Amer and Qayyum found that if blood vitamin D levels are increased, the result is lower levels of CRP (c-reactive protein), a popular marker for cardiovascular inflammation.
However, excessive vitamin D levels may be bad for you - any vitamin D levels above 21 nanograms per milliliter were found to be linked to an increase in CRP, which is associated with the hardening of blood vessels and a greater risk of developing cardiovascular problems.
The team has also found a link between excess vitamin D and raised levels of homocysteine, which can increase the risk of cardiovascular diseases.
Dr. Amer urges people to check with their doctors before considering vitamin D supplements - ideally, they should have their vitamin D blood levels checked.
Even if your doctor recommends supplementation for you, you should beware when reading the labels. A report published in JAMA Internal Medicine found that many OTC vitamin D supplements have less of the vitamin than their labels claim (OTC means "over-the-counter", non-prescription).
Amer added:
"Most healthy people are unlikely to find that supplementation prevents cardiovascular diseases or extends their lives," and there is no consensus among doctors on what is the right level of vitamin D in the blood for healthy people.There are a lot of myths out there and not enough data."
This study is supported by a grant from the National Heart Lung and Blood Institute (1K23HL105897-01).
A team from Boston University School of Medicine reported in the journal PLoS ONE (March 2013 issue) that higher vitamin D levels in healthy people have an impact on genes involved in many biologic pathways associated with cardiovascular, autoimmune and infectious diseases, as well as cancer.The authors say that healthy people who improve their vitamin D status have considerably better immunity against disease.
In another study carried out at Dextrel University, also published in PLoS ONE (February 2013 issue), scientists found a link between obesity and vitamin D deficiency - they found that obesity can cause vitamin D deficiency. The study involved 42,000 people in more than 21 countries.
Interesting further reading: "Should I Take Vitamin And Mineral Supplements?"
Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today
Muhammad Amer, MD, MHS, FACP and Rehan Qayyum, MD, MHS
The American Journal of Medicine - 18 April 2013 (10.1016/j.amjmed.2012.11.021) Please use one of the following formats to cite this article in your essay, paper or report:
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6 May. 2013.
Please note: If no author information is provided, the source is cited instead.
posted by William B. Grant on 6 May 2013 at 5:08 pm
There is one graph in the paper showing hazard ratio (HR) for all-cause and cardiovascular disease mortality rates vs. vitamin D levels. The HRs decrease rapidly as vitamin D increases from 4 ng/ml to 21 ng/ml, then slowly as vitamin D increased to 65 ng/ml. The uncertainty in the HR for cardiovascular disease mortality rate becomes so large for vitamin D above 30 ng/ml that no conclusion is possible.
There are many such curves in the journal literature for all-cause mortality, cancer, etc. In general, benefits of vitamin D increase dramatically to about 30 ng/ml, but some studies show benefits to at least 40 ng/ml.
There have not been any reports in the literature for adverse effects of vitamin D for levels below 80-100 ng/ml that cannot be ascribed to problems with the study. For example, some of those enrolled in observational studies have been advised by their physician to take vitamin D supplements because they had a vitamin D deficiency disease such as osteoporosis.
Taking vitamin D late in life cannot correct all of the adverse effects of vitamin D deficiency early in life.
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posted by Price Weston on 6 May 2013 at 1:53 pm
See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868557/
Lifeguards, which have 2.5 timed blood levels of vitamin D compared to the average population and who's levels are more likely closer to paleo norms of hunter gathers would expect to see very dramatic increases in in diseases if the above article is to be believed. I suspect that optimum is much higher than the sun deficient minimum called for in the above bad writeup.
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posted by Pete on 6 May 2013 at 1:10 pm
If you read the paper this press release is based on you will find the warnings about vitamin d above 21ng/mL are nowhere are strongly worded. There are at least 2 reasons why a person may have higher vitamin d levels. 1) they make/consume more vitamin d, 2) there bodies are better at conserving vitamin d by turning off genes, like those that reduce inflammation. As they appear not to have taken multiple measurements of 25(OH)D or worked out why these people had slightly higher vitamin d levels they cannot be certain that those over 21ng/mL actually have excess vitamin d or are in fact severely deficient and would get healthier if they took more. So in basic terms the results do a poor job of supporting the conclusions present here, which is why they are not in the journal paper.
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'Vitamin D Supplementation - Be Careful, Researchers Warn'
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