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Vitamin D supplements?
Posted: 03 August 2009 09:33 AM   [ Ignore ]   [ # 16 ]
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George - 03 August 2009 09:29 AM

Which makes me think: the 1,000-IU pill per day is a recommended dose for whom? For people with white skin?

No, there was nothing in there about skin color. There was some discussion on one of the links I provided that people in northern latitudes are of greater risk of getting too little sun-based vitamin D. But it sounds as though this is quite a general problem—assuming it is a problem at all, of course.

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Posted: 03 August 2009 09:37 AM   [ Ignore ]   [ # 17 ]
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macgyver - 03 August 2009 09:32 AM

I personally believe that they are all jumping the gun. While they are all published by reputable outfits, I think that the pressure to provide leading edge medical advice leads many lay publications to make recommendations before the evidence is all in because they dont want to be “late to the ball”. I personally dont think the evidence is sufficient.

You ask an important question? Is it harmful for an adult to take 1000iu of Vit D every day? If you’re asking about acute dramatic harmful effects the answer is no. This is sort of like asking about the beneficial effects. There is no doubt that Vit D can prevents significant and severe illnesses like rickets and osteomalacia, but when you’re talking about illnesses that may only occur inn a small portion of the population ( as is the case when your talking about an increase in cancer or heart attack death rates for example) then it takes large long term prospective studies to work that out just like it will take those sorts of studies to determine if the current beneficial claims are in fact real. When you’re advising people to do something that may only have a marginal benefit you’re obligated to prove that it does not also have a marginal risk.

Fair enough. For now it would appear that there is no additional marginal risk, although admittedly there is always a possibility that such risk will appear in the data later on, as is the possibility that it will provide additional marginal benefit. As I say, given the credibility of the sources here, from my lay point of view this information has passed the threshold of plausibility, which is why I am taking action based upon it.

However it has only just passed that threshold for me. As I say, I am all ears for disconfirming evidence.

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Posted: 03 August 2009 10:09 AM   [ Ignore ]   [ # 18 ]
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Thats reasonable doug, but keep in mind that no one knew about the ability of VitA to increase lung cancer risk until a controlled trial was done. Again, your hoping for marginal benefits that may or may not be real and no one has really studied the possibility of marginal risks. I honestly don’t think there will be any, but the level of evidence I need as a physician before making a recommendation to someone is obviously different from the level of evidence an individual such as yourself would need before making a decision for themselves. I really think all three of those publications should have required a higher level of evidence since they are making a public recommendation.

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Posted: 03 August 2009 10:31 AM   [ Ignore ]   [ # 19 ]
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macgyver - 03 August 2009 10:09 AM

Thats reasonable doug, but keep in mind that no one knew about the ability of VitA to increase lung cancer risk until a controlled trial was done. Again, your hoping for marginal benefits that may or may not be real and no one has really studied the possibility of marginal risks. I honestly don’t think there will be any, but the level of evidence I need as a physician before making a recommendation to someone is obviously different from the level of evidence an individual such as yourself would need before making a decision for themselves. I really think all three of those publications should have required a higher level of evidence since they are making a public recommendation.

Sure, every physician has to be comfortable with the validity of anything they recommend to their patients.

Do you have a good idea of the strengths and weaknesses of the studies these publications used to make their findings? Have you looked at them? I’d be interested to know.

I do recall going to a talk a couple of years ago sponsored by CFI, of I believe it was Dr. Walter Willett from the Harvard School of Public Health about the dangers of trans-fats. It’s basically his studies that got trans-fats out of the food chain. Now, all his best data were from the Nurses’ Health Study, an epidemiological study, not double blinded. The problem with these sorts of cases is it’s nearly impossible to get a double blinded study done. It would cost too much to fund. So you do eventually have to rely on studies of lower quality, and it’s basically a question of risk versus reward.

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Posted: 03 August 2009 10:49 AM   [ Ignore ]   [ # 20 ]
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I’m sorry I can’t quote you or link you any of the studies right now. I would have to take the time to search for them and I’m kind of busy at the moment. I have read a number of them as they came out over the past couple years and every study I read was a population based retrospective analysis as I recall. Its actually not hard to do these studies ( not to beat a dead horse, but the Vit A study is a good example). It just takes time and money. Unfortunately everyone wants an answer today and some of these studies might take 20 years to do.

There are a number of different claims that have been made for Vit D. When I have some time I’ll try to get the studies for you and post them here, but the Harvard letter itself implies that the studies are very tentative just in its very wording.

“Heart and blood vessels. Low levels of vitamin D have been linked to high blood pressure in several studies, but further research is needed to determine whether consuming additional vitamin D—either in food or pills—lowers blood pressure or heart attack risk.

Cancer. Higher blood levels of vitamin D have been linked to a lower risk of colon, prostate, breast, and lung cancers, along with lower mortality from some of these cancers. A 2007 study in The European Journal of Cancer compared cancer rates in sunny countries with those in less sunny climes. The study, which involved 13 cancer registries with over four million people, showed that vitamin D production in the skin (which occurs with exposure to sunlight) may lower the risk of several forms of cancer, especially stomach, colorectal, liver and gallbladder, pancreas, lung, breast, prostate, bladder, and kidney—but only in people who live in sunny regions.”

The constant use of the word “linked” should be a red flag that further research is needed.

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Posted: 03 August 2009 11:43 AM   [ Ignore ]   [ # 21 ]
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macgyver - 03 August 2009 10:49 AM

The constant use of the word “linked” should be a red flag that further research is needed.

Doubtless further research is needed. The question the editors of these sorts of journals ask themselves is whether there is a preponderance of the evidence such that the risk reward is in favor of publishing, as was in the case of trans-fats, an epidemiological study being of significantly less precision than a carefully controlled, double blinded study.

Then it comes down to the respect with which you hold the journal, and whether there are other similarly respected journals which disagree. On the latter issue, I don’t yet know of any. Perhaps some do?

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Posted: 03 August 2009 01:01 PM   [ Ignore ]   [ # 22 ]
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Perhaps until further studies are available and everyone can agree, a happy medium for those who really want to take a supplement, would be to take a smaller sized one. For example, the ‘400 size’ pill that is available vs. the ‘1000 size’ whopper? Just a thought.

It might be a good idea to keep a daily food journal during an average week, and roughly calculate how much you’re getting per day of key vitamins. Those with a rich or healthy diet may find that they already get the recommended amount of Vitamin D. There are a few online food journals available, and I think there is an iPhone app as well.

And of course, talk to your doctor. What do I know? cheese

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Posted: 03 August 2009 01:12 PM   [ Ignore ]   [ # 23 ]
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Jules - 03 August 2009 01:01 PM

It might be a good idea to keep a daily food journal during an average week, and roughly calculate how much you’re getting per day of key vitamins. Those with a rich or healthy diet may find that they already get the recommended amount of Vitamin D.

Well, it seems that apart from some fish (salmon, mackerel), vitamin D is really not available in many foods in large quantities, and you would have to drink really a LOT of fortified milk to get even 400 IU (four cups a day). Premodern humans got it almost entirely from sun exposure, it would seem.

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Posted: 03 August 2009 01:48 PM   [ Ignore ]   [ # 24 ]
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The Institute of Medicine of the National Academy of Science in 2007 updated the maximum safe level of daily intake oof vitamin D to 10,000 I.U.  In the past they had listed it as 2000 I.U.  So, it would seem that there is a decent amount of information that indicates that 1000 I.U. daily isn’t likely to be dangerous.

I agree with Macgyver that carefully controlled double-blind studies are by far the best, but in the absence of them a fairly large number of separate studies that all appear to agree would seem to indicate some value to increasing one’s vitamin D intake. 

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Posted: 03 August 2009 04:03 PM   [ Ignore ]   [ # 25 ]
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dougsmith - 03 August 2009 01:12 PM
Jules - 03 August 2009 01:01 PM

It might be a good idea to keep a daily food journal during an average week, and roughly calculate how much you’re getting per day of key vitamins. Those with a rich or healthy diet may find that they already get the recommended amount of Vitamin D.

Well, it seems that apart from some fish (salmon, mackerel), vitamin D is really not available in many foods in large quantities, and you would have to drink really a LOT of fortified milk to get even 400 IU (four cups a day). Premodern humans got it almost entirely from sun exposure, it would seem.

Hmmm, I suppose that is a LOT of milk. We’d all be rich in Vitamin D and gas.  LOL

I would like to add, however, that women may be getting a higher intake via diet than men, and perhaps this is where I’m thinking differently from the group here.

Women are frequently encouraged to eat a lot of dairy, a few servings per day, and most all of it is fortified these days. At least in my experience, at both my internist and GYN checkups, it’s hinted that if we don’t eat lots of dairy we’ll become old hunchbacks at menopause - society will shun us and we will start collecting stray cats and precious moments figurines… just kidding.

But it’s been my experience that women are encouraged to have a few servings of dairy per day for calcium, to help ward off osteoporosis. I never paid it much heed, and I hear a little bit less about it these days than in years past. Perhaps its not as encouraged anymore, or perhaps I’m just not hearing it anymore. I happen to like yogurt and cheese, so I’m sure I get enough calcium.

So anyhow, a woman eating all those fortified dairy products out of concern for calcium may also be getting quite a bit of fortified Vitamin D, unintentionally. Perhaps not the entire recommended amount in the newer guidelines, but perhaps enough to prevent a deficiency?

Again - ramblings of a lady with no nutritional expertise, just throwing it out there for conversation.  wink

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Posted: 03 August 2009 04:22 PM   [ Ignore ]   [ # 26 ]
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Occam - 03 August 2009 01:48 PM

The Institute of Medicine of the National Academy of Science in 2007 updated the maximum safe level of daily intake oof vitamin D to 10,000 I.U.  In the past they had listed it as 2000 I.U.  So, it would seem that there is a decent amount of information that indicates that 1000 I.U. daily isn’t likely to be dangerous.

I agree with Macgyver that carefully controlled double-blind studies are by far the best, but in the absence of them a fairly large number of separate studies that all appear to agree would seem to indicate some value to increasing one’s vitamin D intake. 

Occam

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occam those figures are correct but they are only concerned with acute toxicity not long term subtle effects that may incease the risk of cancer, heart disease, or other diseases

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Posted: 04 August 2009 04:21 AM   [ Ignore ]   [ # 27 ]
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Jules - 03 August 2009 04:03 PM

So anyhow, a woman eating all those fortified dairy products out of concern for calcium may also be getting quite a bit of fortified Vitamin D, unintentionally. Perhaps not the entire recommended amount in the newer guidelines, but perhaps enough to prevent a deficiency?

Well, the Harvard page I mentioned earlier (HERE) suggests targeting 2,000 IU/day; so if you take a 1,000 IU pill, that still assumes you get 1,000 IU from other sources during the day. And given the data, I don’t think anyone gets that much unless they really pig out on fortified dairy and mackerel, or get a lot of sun exposure. (3 cups of fortified milk and 7 oz. mackerel gets you to 990 IU. I am sure virtually nobody eats that type of diet every day; I certainly don’t, and wouldn’t).

And it is worth noting that as a result, even the Harvard page, which is at the high end of the recommendations, doesn’t even get us to 2,000 IU/day, which is the upper safe limit of the suggested daily amount of vitamin D even under the old (pre-2007) NAS recommendations. I would expect that they have plenty of longer-term evidence of human consumption at this level, making the possibility of any significant harm unlikely.

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Posted: 04 August 2009 02:55 PM   [ Ignore ]   [ # 28 ]
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OK, I’ve done a little further searching, and THIS editorial in the American Journal of Clinical Nutrition (Vol. 85, No. 3, 649-650, March 2007) appears to be a nexus point for the present issues with vitamin D. It’s titled “The urgent need to recommend an intake of vitamin D that is effective”.

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Posted: 04 August 2009 03:23 PM   [ Ignore ]   [ # 29 ]
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dougsmith - 04 August 2009 04:21 AM

(3 cups of fortified milk and 7 oz. mackerel gets you to 990 IU. I am sure virtually nobody eats that type of diet every day; I certainly don’t, and wouldn’t).

Oh come on now, I know you secretly prepare a jumbo milk and mackerel smoothie in the blender each morning. Breakfast of champions.  LOL 

It does appear at this time that a minor supplement of Vitamin D is unlikely to cause harm and could prove beneficial. However, I must tease that it’s the fault of CFI forums that I’m wary of any supplement! You’ve all made a vitamin skeptic out of me in topics past.  wink

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Posted: 04 August 2009 05:07 PM   [ Ignore ]   [ # 30 ]
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Jules - 04 August 2009 03:23 PM

However, I must tease that it’s the fault of CFI forums that I’m wary of any supplement! You’ve all made a vitamin skeptic out of me in topics past.  wink

Ha! Well, it always pays to be a skeptic. I’ll be interested if others come with further info on this topic ...

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