You are likely aware that a committee of the Institute of Medicine has just issued recommendations for calcium and vitamin D intake. The big news is that the committee is recommending not as much more of both nutrients as enthusiasts might have hoped, and sounds a precautionary note about excess dosing.
Are the supplement enthusiasts right, and IOM wrong -- or vice versa? Is the IOM report a reliable basis for your own decisions?
Let's start with the strong points of both the IOM in general, and this particular report. The Dietary Reference Intakes -- of which the new report is a small part, and home to the RDAs -- are evidence-based. As a scientist and physician, I consider that a good thing, but it comes with caveats nonetheless.
An evidence review is only as good as the available evidence. While the IOM committee report on calcium and vitamin D refers to "1,000 papers reviewed," it says nothing (at least not before accessing the fine print) about the quality of those papers. But since I know this literature fairly well, I can tell you: not great.
We simply do not have large scale, long-term intervention trials with all the bells and whistles -- randomization, double-blinding, placebo-control -- to tell us what dose of calcium or vitamin D is truly optimal for health. The science we do have, no matter how many papers are cited, has major gaps in it, which must be filled with judgment.
The judgment of the IOM panel is sound, as are their cautious conclusions which, fundamentally, suggest that we stick close to the calcium intake previously recommended about a decade ago and not go higher, and roughly double our intake of vitamin D daily (to between 400 and 600 IU), but not more.
These cautious conclusions are based on studies that fail to show clear benefits of higher doses, and studies that suggest (but do not prove) the possibility of harm. They are also based on the prime directive of biomedicine -- "first do no harm," and its cousin, the precautionary principle. The precautionary principle basically says to take the path of least risk when in doubt, and that is what the IOM committee appears, quite reasonably, to have done.
But of course, being cautious does not reliably mean being right. While there is some potential evidence for absence of benefit from calcium and vitamin D supplements, there is to a much greater degree absence of evidence. Again, the definitive trials simply haven't been conducted, mainly due to cost and other difficulties.
When evidence is in shorter supply than one might like, science routinely turns to models and theories to guide the judgment required to plug the gaps. Two such models are handy: transcultural comparisons and paleoanthropology.
Transcultural comparisons allow us to see variations in human health associated with variations in exposures to nutrients, among other things. Such observational assessments cannot prove cause and effect, but they are useful for general guidance.
Transcultural comparisons fully back up the IOM's conclusion about calcium. Most populations around the world actually consume less than we do in the U.S., yet have fewer cases of osteoporosis. This may be due to more weight-bearing exercise elsewhere, less protein and acid in the diet, and more sun exposure -- and thus higher levels of vitamin D. We don't really know, but we do know it is possible to have healthy bones without increasing calcium intake above the RDA in the former and current IOM reports -- and indeed, to get there with less.
But vitamin D is another story. Paleoanthropology and transcultural comparisons both suggest that humans with more sun exposure nearer the equator live with higher vitamin D levels than their house-bound, temperate climate counter-parts. We find ourselves relying on dietary vitamin D to compensate to a marked reduction in levels 'normally' produced by the work of sunlight on our skin.
The back story here is fascinating. All humans were originally dark-skinned, or black if you will. A genetic mutation resulted in pale (white) skin, and that spread in populations away from the equator because it conferred a survival advantage (the reason mutations spread). The particular advantage was more efficient production of vitamin D in limited light by paler skin.
So I think there is still a theoretical basis for more vitamin D than clinical trials permit us to recommend with confidence. The IOM may, in other words, have been a bit too cautious in this case.
Here's where all of this leaves us: Haphazard fortification of the food supply with the darling nutrients du jour is a bad idea, and always was. When this is done, there is no predicting what dose or unbalanced combination of nutrients you may consume over the course of a day. Some judicious fortification makes sense, but when every processed food contains calcium, or vitamin D, you are indeed at risk of inappropriate doses. The IOM report rightly sounds an alarm about these prevalent and misleading practices.
Calcium supplementation by adolescent girls and adult women may make sense, although calcium from foods, including low and non fat dairy, is likely preferable. There are other therapeutic roles for calcium as well, such as treating PMS. It would be very appropriate for individualized decision making, ideally based on a discussion between each woman and her gynecologist or primary care physician.
I am less convinced by the IOM's cautious interpretation of the vitamin D literature, however. I find that many of my patients, when tested, do indeed have very low blood levels. Sun exposure is limited in much of the U.S. during much of the year. And while definitive evidence to support high dose vitamin D supplementation is lacking, there are hints of benefits in many studies with dosing above the IOM recommendation of 400 IU daily.
My advice about vitamin D, therefore, remains much as it was: Get outdoor activity whenever possible, and let sunlight work its magic. If you can't get a good 20 minutes a day of sun exposure, dietary vitamin D is essential. It can come from fortified food, but a supplement is a very reasonable insurance policy. A supplement of 400 IU daily ensures you will get the recommended dose, at least. Higher doses may be warranted, but should be discussed with your physician. You are unlikely to suffer any harm from doses up to 2,000 IU per day, but I hasten to add that we don't have long term intervention trials to prove harmlessness any more than we do to prove benefit.
Calcium and vitamin D are important nutrients. As with all nutrients, enough is good -- too little or too much is bad. The IOM invokes the precautionary principle to offer recommendations that are reasonable, and willfully conservative. But a relative absence of evidence means that guidance is as much about judgment as science.
My judgment, and familiarity with the literature, leaves me quite comfortable with the IOM conclusion about calcium, but with a bit more doubt regarding their conclusions for vitamin D.
In the absence of decisive evidence, your own decisions must also depend in the end on the evidence presented to you, and your own good judgment. Apply at will.
Dr. David L. Katz; www.davidkatzmd.com
www.turnthetidefoundation.org
Follow David Katz, M.D. on Twitter: www.twitter.com/DrDavidKatz
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And don't take calcium unless you are also taking magnesium!!! Please, extra calcium is not good by itself.
I wish to point out that the THYROID and the PARATHYROID are not the same organ. What I wrote earlier about hypercalcemia refers to the PARATHYROID not the thyroid. Do not mix them up.
Hyper-parathyroidism has two main types Primary and Secondary, with Secondary taking vitamin d will make you better in Primary it will make you worse. It is better to identify these illnesses early so they are not a reason to avoid vitamin d supplements/ avoid sun exposure.
Vitamin D3 is the stuff made in the skin (or in D3 tablets). It stores as 25(OH)D in the blood (this is what you are trying to get to the correct level). Calcium levels are controlled by 1,25(OH)D. Raising your 25(OH)D levels to the correct level actually lowers your 1,25(OH)D level thus reducing the risk of calcification not raising it.
Vitamin d is used as a rat poison because it kills them efficiently but it is very difficult to kill people by accident (unlike warfarin).
It is not true that melanin blocks the wavelengths which synthesize vitamin D . The value of melanin as a sunscreen (2010).
“epidermal melanin is not a neutral density filter providing no or minimal protection for the induction of erythema at 295 and 315 nm and some protection at 305 and 365 nm”
. Blood vitamin D levels in relation to genetic estimation of African ancestry “found novel evidence that the level of African ancestry [rather than skin pigmentation] may play a role in clinical vitamin D status”.
There is a negative feedback system; evolution has has got vitamin D levels just right
Klotho protein deficiency and aging.
“α-Klotho protein is shown to function in the negative feedback regulation of vitamin D3 synthesis These observations indicated that abnormal vitamin D3 metabolism is the main cause of aging phenotypes.″
Klotho was named after one of the Moirae or fates, supplementing vitamin D is indeed a fateful step.
People of tropical ancestry have a optimum homeostasis of vitamin D which is below the new IoM level. Attaining them will require supplements
If white skin evolved for vitamin d production you would have to look specifically at what happens in spring and autumn. It is likely to do with how long the vitamin d winter is, not the ability to produce vitamin d in the summer. So you would have to look at what happens with lower energy UVB and efficiency at lower intensities.
in its headline to the report Dr Katz referred to. Patently false.
"...based on the prime directive of biomedicine -- "first do no harm," and its cousin, the precautionary principle. The precautionary principle basically says to take the path of least risk when in doubt, and that is what the IOM committee appears, quite reasonably, to have done..."
While the IOM seems to respect this ideal more than say, the FDA, or any pharmaceutical company, it is still a long way from being their guiding principle.
Oh, and vitamin D toxicity? Merck lays out the generally accepted facts:
"...Vitamin D 1000 μg (40,000 IU)/day produces toxicity within 1 to 4 mo in infants. In adults, taking 1250 μg (50,000 IU)/day for several months can produce toxicity..."
http://www.merckmanuals.com/professional/sec01/ch004/ch004k.html
Reasonable people need not fear a vitamin D overdose.
Thank you Dr. Katz...well said!
My wife and I have been discussing calc and vitamin D for the last few weeks and this write-up really helps to clear up the fog created by the IOM.
All they did was make things more confusing and created more questions...which, I guess in a sense is a good thing as it lead us here to read your words.
I am 32 and my wife is 33, we have a 3 year old daughter and we just moved from San Diego to Michigan. Big difference in many ways...especially the cloudy factor.
We've been upping our vitamin D intake and monitoring our daughter very closely for any changes to her behavior, overall energy level and fine motor skills.
She's doing fine and we feel great.
Looking forward to more articles!
Peace.
She came to live with me and her physician put her on a multi-vitamin (in addition to the calcium supplements). The vitamin also had calcium. She then became very ill (nearly died). And after running tests, it was determined that she was overdosing on the calcium. She stopped taking the vitamin and the supplements and her appetite returned.
She was seen by various doctors throughout her nursing home stay and not single one gave thought that the calcium might be suppressing her appetite. In fact, her new physician when she came to live w/me, added to it!
Personally, I think she initially lost weight as a result of the hip surgery which made the 2 bills too much. Why didn't the doctors address this? Is that not common?
I still struggle to understand why none of the doctors were able to identify the calcium dosage as a possible cause of the loss of appetite and also why the home physician did not take the dosage into account before prescribing the additional multi-vitamin.
So, Dr. Katz where exactly are you getting your research data from? Show us some of your studies and respected published medical journals to back up this nonsense.
I wouldn't trust as you as my doctor and you should be ashamed of yourself for giving out false information...
http://drumlib.com