Most people in the research the IOM assessed had what the group considered sufficient levels of 25-hydroxyvitamin D (50 nanomoles per liter as measured in the U.S. and 20 nanograms per mole as measured in Canada) despite not meeting daily intake recommendations. This incongruity suggests that despite increased caution about sun exposure to avoid skin cancer, people are still getting a substantial amount of vitamin D from natural synthesis. To be safe, however, the committee made their intake suggestions based "on the assumption of minimum sun exposure," Ross said.
Hanley worked with researchers from Osteoporosis Canada who published recommendations this summer in the Canadian Medical Association Journal, and they recommended 400 to 1,000 IU per day for optimum bone health in those 50 and younger. But the two recommendations fall within a comfortable range of one another. "We're not talking about major differences here," Hanley says. "These recommendations would be an improvement on what we have now," he notes. "Where the argument might come in is: What's optimal for bone?" His group's recommendations are likely higher because they were focused on bone health—as well as a population that generally receives less sunlight in winter months.
Deficient evidence
Despite having assessed 1,000 studies and reports and "listened to testimony from scientists and stakeholders" the IOM committee found that most published health benefits (aside from bone strength) provided "mixed and inconclusive results and could not be considered reliable," according to the report, which was commissioned by the U.S. and Canadian governments.
Evidence that vitamin D plays a role in fending off some cancers or preventing cardiovascular disease has emerged "largely through association, identified through population studies and not through controlled trials," Hanley says. "So it's not high-level evidence." Nevertheless, he notes, "it's probably true that vitamin D is important in many body systems" Hanley points out that some studies have uncovered a link between very high levels of 25-hydroxyvitamin D and pancreatic cancers, whereas other studies have found very low levels of the vitamin associated with the cancer. "None of the findings in relationship to cancer—both benefit and harm—are consistent," he says.
It may well be a matter of research catching up to biology. To really home in on the ideal levels of vitamin D, Hanley recommends studies that follow people deficient in vitamin D who are randomly assigned to a supplement or placebo group. "What were missing were studies of cause and effect," Ross explained.
Too much of a good thing
The IOM conclusions at least may stop those who may be getting excessive vitamin D and calcium via supplements. Too much vitamin D hurts the heart and kidneys, and too much calcium can lead to kidney stones. Other side effects include increased risk of death from any cause as well as increased risk of fractures, falls and possibly some cancers, the authors of the report noted in a summary.
So one of the committee's changes was trying to figure out "how much is too much" of these crucial nutrients, Ross explained. Previous evidence has shown definitive increase in harm for those taking more than 10,000 IU of vitamin D a day, but "we took a cautious approach" in assigning new upper limits, Ross said.
Nevertheless, the upper limit of 4,000 IU/day of vitamin D should not be a goal, Jones noted. "We don't recognize any benefit from taking a dose" between the recommended daily allowance and the top levels considered safe, he said.
Ross noted that the new recommendations will "have a shelf life of many years" in terms of setting health recommendations—influencing everything from nutritional labeling to school lunch composition.
In the meantime, there is "an urgent need" to standardize blood tests, Ross said. Currently, one person might be declared vitamin D deficient or sufficient depending on which test they are given. And for now, some experts recommend scaling back on the amount of screening for vitamin D deficiency. Such tests "probably should not be part of routine care," Steven Clinton, a professor of hematology and oncology at the Ohio State University and review committee member, said at the briefing. In the next decade, as tests become more consistent and more studies are done, he said, doctors will likely be able to provide patients personalized recommendations for vitamin D and calcium intake based on their family history and genetic profile.
But many more tests and trials remain to be done, not only to zero in on optimum doses of the nutrients, but also to explore their role in the human body. "As a basic scientist, I am still very excited about this molecule, which regulates hundreds—maybe thousands—of genes in the body," Jones said.
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7 Comments
Add CommentWhy should we always follow these so-called experts' suggestion? So many illiterate people don't know anything about the suggestions, but still live healthy. Therefore a healthy lifestyle can promote our definite health, exercise regularly, not picky to food and so on.
Reply | Report Abuse | Link to thisMilligrams, international units, ounces ... why not include barleycorns and drachms. Mixing units in an article is deliberate obfuscation.
Reply | Report Abuse | Link to thisKeeping the population low in vitamin D lowers the average IQ and increases votes for the republicans.
Am I missing something here, or is this again a case where somebody is mixing together multipliers milli (10e-3) and micro (10e-6)? As far as I have educated myself, there is equivalence between 400 IU and 10 micrograms of vitamin D. This article is using units of mg ie milligrams. Typical shorthands are mg for milligram and ug for microgram (actually greek letter myy = micro). Sometimes people use mcg also for micrograms. But writing about milligrams with vitamin D, I find that very dangerous. That is how people who don't know better could get overdosed. I think this is because some people think that microgram is shorthanded as mg, which it is not as above noted.
Reply | Report Abuse | Link to thisWell, I'm glad they've at least taken the time to demonstrate that all of this vitamin D hysteria is bunk. Nobody ever seems to notice that many of the ailments attributed to vitamin D deficiency also cause people to reduce their exposure to sunshine, thereby lowering vitamin D intake. All the epidemiological studies and multivariate analyses in the world won't get you out of this confound.
Reply | Report Abuse | Link to thisThe opening paragraph pretty clearly associates the abbreviation mg with milligrams:
Reply | Report Abuse | Link to this"The new assessment recommends a daily vitamin D dietary allowance of 600 milligrams for most healthy people 9 years and older (with an estimated average requirement of 400 International Units per day—and no more than 4,000 IU of vitamin D per day). People 71 years and older should take 800 mg of the vitamin per day, according to the report. (Children aged 4 to 8 years should not have more than 3,000 IU/day and those aged 1 to 3 years should not have more than 2,500 IU/day.)"
I know little of these things, but the switching between mg and IU in this article is sloppy and confusing. I find IU (International Units) to be confusing anyway, since the relationship between IU and any standard unit (i.e., mg) varies by solution. I have no idea, but was the relationship of IUs and micrograms based on some other substance?
This switch back and forth from IUs and standard units seems to be pretty common and is dangerous for regular folks. If this practice is to be continued some method of conversion is required.
As for all the changes, this seems to me to be much to-do about not much of anything. I think that if this article had included a simple chart of age groups / old and new it would have been pretty short and sweet.
To ztansfi. It always make me so happy to find people who just plain know it all. Unfortunately, if such sceptics always were allowed to dominate the developments in medicine or other knowledge, nothing new would ever come out. Be a bit humble. There just may be something here, considering the large amounts of vitamin D produced by sunshine, clothes off, and the dietary recommendations for people who live mainly indoors in cold climates most of the year. We are just at the beginning of this research, so never kill a child. It may grow up to be a good person.
Reply | Report Abuse | Link to thisAnd if I can't get enough of sunshine daily, can I just entrust myself to a vitamin D supplement? Is that okay? Also, I stumbled upon this site: <a href="http://www.mercola.com/Downloads/bonus/vitamin-d/report.aspx">http://www.mercola.com/Downloads/bonus/vitamin-d/report.aspx</a> and found out that sunscreens are not safe to be used. So, don't mind using one.
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