Low vitamin D status associated with cognitive decline: Study

Inadequate dietary intake of vitamin D is associated with higher levels of cognitive impairment; however it remains unclear if the link is causal, according to a new study.

The study, published in Neurology, suggests that a weekly intake of less than 35 micrograms of vitamin D is associated with a greater incidence of cognitive impairment. However the researchers noted that the association could be causal in either direction, stating it is possible that low vitamin D is a result of, rather than the cause of cognitive impairment.

“The main finding of this population based study …was that the weekly dietary intake of vitamin D was significantly associated with the global cognitive performance in both linear and logistic regression models, even while considering the effects of all potential confounders,” said the researchers, led by Dr Cédric Annweiler from Angers University Hospital, France.

D and cognitive decline

Cognitive performance declines naturally as we age, but it has been suggested that vitamin D status could impact on cognitive function among older adults.

It is suggested that vitamin D binds to neuronal receptors in the brain, and develops an anti-neurodegenerative action through, anti-inflammatory and antioxidative. Many people have therefore recommended that maintaining an adequate vitamin D status is essential to avoid vitamin D deficiency– induced cognitive decline.

Data from David Llewellyn and colleagues at the University of Exeter, England, indicated that insufficient levels of vitamin D may accelerate cognitive decline . The scientists analyzed vitamin D levels from blood samples of 858 adults and found that severe vitamin D deficiency was associated with a 60 percent increase in the risk of substantial cognitive decline.

Annweiler and colleagues said the benefits of vitamin D intake in treating or preventing cognitive impairment remain unknown, adding that, to date no randomized controlled trials have explored the benefits of vitamin D supplementation to treat or prevent cognitive impairment.

But, before conducting such a trial, they said it would be of benefit to determine whether dietary, non-supplemented, intake of vitamin D could be associated with cognitive performance in older adults.

“We had the opportunity to examine the association between dietary intakes of vitamin D and global cognitive performance in a large representative community survey of older women,” said the researchers.

Study details

A total of 5,596 women, not taking vitamin D supplements were divided into 2 groups according to their baseline weekly staus: either inadequate (less than 35 micrograms per week) or recommended (more than 35 micrograms per week).

Compared to women with recommended weekly vitamin D dietary intakes, women with inadequate intakes were reported to have lower scores on the SPMSQ mental state questionnaire.

The researchers observed that inadequate intakes were more often associated with cognitive impairment, as defined by an SPMSQ score of less than 8.

“We found an association between weekly vitamin D dietary intake and SPMSQ score. Inadequate weekly vitamin D dietary intakes were also associated with cognitive impairment,” wrote the researchers.

Causation

Exactly how low dietary intakes of vitamin D and decreased cognitive performance are associated remains unclear. Annweiler and co workers noted that it is yet to be clarified whether the of association is causal, and if so, in what direction the causation may be.

They stated that it remains a possibility that low vitamin D status may be a result of poor diet, due to cognitive decline. But, emphasized that vitamin D insufficiency has been suggested as a contributing factor to hypertension, which itself is a major risk factor in the development of cerebrovascular diseases and cognitive decline.

Annweiler and colleagues added that nutrients are not consumed in isolation, “but rather as components of an overall diet, which is precisely considered as a modifiable risk factor for cognitive decline.”

Moreover, they said that as a component of diet, low vitamin D intake may be a surrogate measure for other nutritional abnormalities, which in turn may lead to cognitive decline.



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U.S. panel expresses caution on Vitamin D

Government scientists on Tuesday tripled the recommended intake of Vitamin D for most Americans. At the same time, the federal panel cautioned that most people already get enough - and should be skeptical of myriad reports that far higher amounts offer benefits for diseases ranging from cancer to diabetes.

The impact of the advice - coming after a decade of highly publicized research that has led to gradual changes in mainstream medical practice and dramatic increases in over-the-counter supplement sales - was unclear.

"Vitamin D has become a really hot topic," said Catharine Ross, a Penn State University nutrition professor, who chaired the panel. "We hope that the report will provide some reassurance to the American and Canadian public" - federal agencies in both countries were the sponsors - "that their Vitamin D status is not nearly as poor as they have been led to think . . . and is consistent with good bone health."

The conclusion that most people now get enough of the "sunshine vitamin" was perhaps the most controversial finding. Although there is no national standard for adequate levels of Vitamin D in the blood, hundreds of recent studies have found associations between low levels and the risk of various disorders.

Few of those studies were able to prove cause-and-effect, however, and the findings often conflicted. As a result, the panel set aside all claims of benefit for Vitamin D except for skeletal health, which has been known for more than a century. Most Americans, they said, get enough for their bones.

"Basically, what is going to happen here is nothing," said a disgusted-sounding Bruce W. Hollis, professor of pediatrics at the Medical University of South Carolina. Hollis, who gave expert testimony to the committee, has found significant benefits to infants whose breast-feeding mothers take 6,000 IU of Vitamin D daily - 10 times the new guideline.

Although the new recommendations of 600 IU per day for most children and adults are triple the old guideline, Hollis and other experts said that was too small to matter.

The panel also made recommendations for calcium, which works with Vitamin D to build bone. Most calcium guidelines stayed the same.

The most significant change from the past, scientists said, is in how the report defines the Vitamin D upper limit, the maximum amount that is likely to pose no risk of adverse effects to almost anyone. The limit previously was another hurdle for scientists who wanted to study supplementation in the higher amounts that they believed would make a difference.

This time, the committee not only set the limit higher, but also made clear that it was not intended to constrain research on subjects who were carefully monitored.

Michael F. Holick, a Boston University medical school professor, predicted that intense interest by the media and the public might influence makers of supplements and fortified foods to take their cues not from the new Recommended Dietary Allowance, but from the upper limit.

"I think they were, you know, being very, very conservative," said Holick, whose book, The Vitamin D Solution, describes benefits for heart disease, rheumatoid arthritis, depression, psoriasis, and several types of cancer.

"The good news is that they at least appreciated that everyone needs more Vitamin D."

Holick, who served on the panel that came up with the old recommendations, in 1997, said the committee was required to follow strict guidelines that would preclude consideration of many studies that he considers valid.

Indeed, the new report describes the difficulty of formulating the first scientifically based guidelines for a nutrient that occurs naturally in a few foods (mainly fatty fish), as a fortified element of many others (milk, orange juice, baby formula), as a common pill, and - in its most natural form - as a product of the skin triggered by sunlight.

It is largely the sunlight part that has caused widespread recent concern about deficiency, as people spend more time indoors or slathered with sunscreen, and as dark-skinned people move from latitudes with more sun to areas with less sun.

The report by the outside panel of the Institute of Medicine, part of the Academy of Sciences, does not need to be confirmed by any other body. On the other hand, for the findings to appear on labels and in federal policy, various agencies must translate its findings.

All of that is voluntary.

Ross, the panel chair, said she hoped the report would encourage doctors to "not just jump on the bandwagon" of Vitamin D deficiency.

Kara M. Nakisbendi, a gynecologist with an integrative medicine practice in Ardmore, said that the report might compel her to "not be as aggressive" in raising her patients' Vitamin D levels, but that she would still aim for essentially double what the report considered enough.

Wendy Warner, a holistic physician in Langhorne, said she, too, had seen enough research - and improvements in patients - that she intended to continue recommending amounts of Vitamin D far greater than the committee's guideline.

The panel spent considerable effort trying to determine levels of Vitamin D that would be safe over a lifetime and cautioned against taking supplements in amounts that it could not prove were OK.

Ross recalled past cases, such as hormone replacement therapy, that for years had shown promise and minimal harm, but were eventually found to be problematic.

Some nutrition researchers argue that such comparisons may be valid for pharmaceuticals, but not for nutrients, which are "essential to health," said Robert P. Heaney, a professor of medicine at Creighton University in Omaha, Neb.

He also suggested that the public had already made up its mind. Domestic sales were $425 million in 2009, 10 times those of 2001, the Nutrition Business Journal found.

And Wal-Mart, Heaney noted, recently introduced Vitamin D capsules with 5,000 IU apiece - nearly 10 times the new guideline for most Americans.

"Once Wal-Mart goes there," he said, "so goes the nation."


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New Guidelines for Vitamin D and Calcium

If you've been confused about the flip-flopping reports on the benefits and risks of vitamin D recently, you're not alone. Health officials were just as baffled about the potential benefits that supplements of vitamin D and calcium could have, as well as how much of the nutrients would be sufficient to improve health.

That's why the Institute of Medicine (IOM), an advisory group established by Congress, was charged by the U.S. and Canadian governments to gather the existing evidence on the health benefits of vitamin D and calcium, and come up with revised guidelines to help the public and the medical community determine the recommend dietary allowance, or RDA, of each nutrient. And according to the committee's analysis, North Americans are not nearly as deficient in vitamin D as we have been led to believe.

The 14-member IOM committee, made up of nutrition and other experts, issued its report on Tuesday, advising that the average adult needs about 600 IU of vitamin D daily, and about 1,000 mg of calcium each day to maintain bone health. Those 71 years or older, however, may need more vitamin D, up to 800 IU a day, to combat deteriorating bone. Because of the lack of sufficient data to date, advice on vitamin D up to this point was not considered as a recommended dietary allowance, which is based on stronger scientific evidence, but rather an adequate intake suggestion, and stood at anywhere from 200 IU to 400 IU for adults. The new recommendations are based on data from more than 1,000 studies, most of which included trials in which volunteers were randomly assigned to receive either vitamin or calcium supplements or a placebo, after which their health outcomes were compared to one another.

In addition, the report states that contrary to previous claims, most Americans are not lacking in vitamin D, and that the majority of adults are in fact well-supplied with the bone-building vitamin. The discrepancy can be traced to the lack of standardization among labs that test for blood levels of the vitamin. Different facilities establish varying thresholds for what they consider to be sufficient levels of vitamin D and that can lead to a misleading perception that more people are deficient.

After studying data on which levels of vitamin D are linked to the most benefit for preventing fractures and maintaining bone health, the IOM committee determined that a blood level of 20 nanogm/mL was sufficient for the average adult. The mistaken belief that Americans are deficient in vitamin D has led some experts to suggest that adults spend more time in the sun, since UV exposure can trigger vitamin D synthesis in the skin. But the committee cautions against that practice, since UV exposure can increase the risk of skin cancer and that risk outweighs the need to boost vitamin D production in the body.

The committee's advice also applies only to nutritional requirements to maintain skeletal health, and should not, says committee member Dr. JoAnn Manson, be interpreted to suggest benefit for any other health condition. In recent years, studies have suggested a link between vitamin D supplementation and a lower risk of heart disease, as well as prevention of cancer, Alzheimer's, diabetes and autoimmune conditions. But after a thorough review of the existing evidence for those diseases, the committee determined that the data on such supplementation and non-bone conditions was “inconsistent, inconclusive as to the cause and effect, and insufficient to inform nutritional requirements,” says Manson. Most of the data drawing these correlations did not come from rigorous clinical trials that randomly assigned subjects to a vitamin or placebo group.

That's not to say that vitamin D will not at some point prove effective in preventing or alleviating conditions other than bone-related fractures; Manson is currently recruiting for a multicenter study, the Vitamin D and Omega-3 Trial, or VITAL, that aims to do just that. VITAL will involve more than 20,000 healthy subjects who will be taking either vitamin D or a placebo and then followed over a number of years for their risk of developing cancer, stroke and heart disease.

VITAL will be the first such large-scale randomized study to analyze vitamin D supplementation in this scientifically validated way, so until those results are released, in another five years or so, the IOM committee declined to make any recommendations about vitamin D's role in anything other than promoting bone health.

The committee also established upper limits of intake per day, since some studies suggest that megadoses of the vitamin D may not provide any additional benefit, and may actually cause harm. Even when it comes to bone health, for example, a recent trial showed that high doses of vitamin D supplementation did not lower the rate of fractures and other studies showed high levels of D increased the risk of kidney stones and other renal conditions. “This perception that more is better and that everyone should jump on the bandwagon of high doses of vitamin D is of concern until we have evidence from randomized clinical trails that the benefits of such dosing outweighs the risks,” says Manson.

The advice is not likely to be the last word on vitamin D and calcium supplementation, and as new data emerges on the role that these nutrients may play in warding off disease, the guidelines may change. But in the meantime, the evidence is strong enough to support supplementing the diet with vitamin D in order to keep bones healthy. Having an RDA for vitamin D, say experts, should help to clear up some of the confusion over D.



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The vitamin D controversy

The group said most people have adequate amounts of vitamin D in their blood supplied by their diets and natural sources like sunshine, the committee says in a report that is to be released on Tuesday.

“For most people, taking extra calcium and vitamin D supplements is not indicated,” said Dr. Clifford J. Rosen, a member of the panel and an osteoporosis expert at the Maine Medical Center Research Institute.

Dr. J. Christopher Gallagher, director of the bone metabolism unit at the Creighton University School of Medicine in Omaha, Neb., agreed, adding, “The onus is on the people who propose extra calcium and vitamin D to show it is safe before they push it on people.”

Over the past few years, the idea that nearly everyone needs extra calcium and vitamin D — especially vitamin D — has swept the nation.

With calcium, adolescent girls may be the only group that is getting too little, the panel found. Older women, on the other hand, may take too much, putting themselves at risk for kidney stones. And there is evidence that excess calcium can increase the risk of heart disease, the group wrote.

As for vitamin D, some prominent doctors have said that most people need supplements or they will be at increased risk for a wide variety of illnesses, including heart disease, cancer and autoimmune diseases.

And these days more and more people know their vitamin D levels because they are being tested for it as part of routine physical exams.

“The number of vitamin D tests has exploded,” said Dennis Black, a reviewer of the report who is a professor of epidemiology and biostatistics at the University of California, San Francisco.

At the same time, vitamin D sales have soared, growing faster than those of any supplement, according to The Nutrition Business Journal. Sales rose 82 percent from 2008 to 2009, reaching $430 million. “Everyone was hoping vitamin D would be kind of a panacea,” Dr. Black said. The report, he added, might quell the craze.

“I think this will have an impact on a lot of primary care providers,” he said.

The 14-member expert committee was convened by the Institute of Medicine, an independent nonprofit scientific body, at the request of the United States and Canadian governments. It was asked to examine the available data — nearly 1,000 publications — to determine how much vitamin D and calcium people were getting, how much was needed for optimal health and how much was too much.

The two nutrients work together for bone health.

Bone health, though, is only one of the benefits that have been attributed to vitamin D, and there is not enough good evidence to support most other claims, the committee said.

Some labs have started reporting levels of less than 30 nanograms of vitamin D per milliliter of blood as a deficiency. With that as a standard, 80 percent of the population would be deemed deficient of vitamin D, Dr. Rosen said. Most people need to take supplements to reach levels above 30 nanograms per milliliter, he added.

But, the committee concluded, a level of 20 to 30 nanograms is all that is needed for bone health, and nearly everyone is in that range.

Vitamin D is being added to more and more foods, said Paul R. Thomas of the Office of Dietary Supplements at the National Institutes of Health. Not only is it in orange juice and milk, but more is being added to breakfast cereals, and it now can be found in very high doses in supplement pills. Most vitamin D pills, he said, used to contain no more than 1,000 international units of it. Now it is easy to find pills, even in places like Wal-Mart, with 5,000 international units. The committee, though, said people need only 600 international units a day.

To assess the amounts of vitamin D and calcium people are getting, the panel looked at national data on diets. Most people, they concluded, get enough calcium from the foods they eat, about 1,000 milligrams a day for most adults (1,200 for women ages 51 to 70).

Vitamin D is more complicated, the group said. In general, most people are not getting enough vitamin D from their diets, but they have enough of the vitamin in their blood, probably because they are also making it naturally after being out in the sun and storing it in their bodies.

The American Society for Bone and Mineral Research and other groups applauded the report. It is “a very balanced set of recommendations,” said Dr. Sundeep Khosla, a Mayo Clinic endocrinologist and the society’s president.

But Andrew Shao, an executive vice president at the Council for Responsible Nutrition, a trade group, said the panel was being overly cautious, especially in its recommendations about vitamin D. He said there was no convincing evidence that people were being harmed by taking supplements, and he said higher levels of vitamin D, in particular, could be beneficial.

Such claims “are not supported by the available evidence,” the committee wrote. They were based on studies that observed populations and concluded that people with lower levels of the vitamin had more of various diseases. Such studies have been misleading and most scientists agree that they cannot determine cause and effect.

It is not clear how or why the claims for high vitamin D levels started, medical experts say. First there were two studies, which turned out to be incorrect, that said people needed 30 nanograms of vitamin D per milliliter of blood, the upper end of what the committee says is a normal range. They were followed by articles and claims and books saying much higher levels — 40 to 50 nanograms or even higher — were needed.

After reviewing the data, the committee concluded that the evidence for the benefits of high levels of vitamin D was “inconsistent and/or conflicting and did not demonstrate causality.”

Evidence also suggests that high levels of vitamin D can increase the risks for fractures and the overall death rate and can raise the risk for other diseases. While those studies are not conclusive, any risk looms large when there is no demonstrable benefit. Those hints of risk are “challenging the concept that ‘more is better,’ ” the committee wrote.

That is what surprised Dr. Black. “We thought that probably higher is better,” he said.

He has changed his mind, and expects others will too: “I think this report will make people more cautious.” (NY Times)



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Vitamin D Deficiency More Prevalent In Winter.... Experts Say Get Tested.

Vitamin D is much more than a vitamin; technically it’s a hormone. Vitamin D is manufactured through exposure to direct sunlight. Once it is metabolized and absorbed, it has profound benefits in nearly every aspect of immunity.

Vitamin D deficiency increases risk for acute sickness as well as susceptibility to chronic diseases, including cancer.

It’s no coincidence that the number of coughs and colds increase in the winter when sunlight is at seasonal low in most climates. The American Journal of Public Health sites over 60 studies that implicate a protective relationship that vitamin D has over cancer. The European Journal of Clinical Nutrition reported that children with low vitamin D levels were 11 times more susceptible to respiratory infections.

The best way to know if you are vitamin D deficient is through a simple blood test. Seek a qualified practitioner who can order a serum 25-hydroxyvitamin D [25 (OH) D] test. The baseline minimum should be 30 ng/mL, although evidence is mounting to establish higher levels for optimal health and cancer prevention. The Vitamin D Council recommends enough sunlight, supplementation and/or artificial light to maintain levels between 80-100 ng/mL year round. Supplementation to increase levels of vitamin D can also be surprisingly inexpensive, especially when one looks at the cost of sick care.

Older adults require higher amounts of vitamin D due to an inability to absorb it efficiently. Research has shown that blacks may require as much as two times the sun exposure to accumulate the same amounts of vitamin D.

The American Journal of Clinical Nutrition performed a study on vitamin D supplementation that showed a decreased incidence of cancer by over 75% compared to those in the placebo group who were given a sugar pill. The best food sources of vitamin D are fatty fish, eggs, meat and mushrooms. Although most people think of vitamin D for osteoporosis prevention it also assists in reducing inflammation and improving neuromuscular function. The Vitamin D Council recommends 2000 IU per day in the summer and 5000 IU in the winter. The Canadian Cancer Society has now officially recommended vitamin D supplements to help reduce risk of cancer.



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