New Vitamin D Guidelines May Raise Advised Dose

SAN DIEGO — The Institute of Medicine is reviewing its 1997 guidelines for vitamin D intake, and will likely recommend increased supplementation when new guidelines are published in 2010.

There is a growing consensus that currently recommended intakes—200 IU per day for individuals under age 50 and 400 IU for those aged 50-70—are too low, said Connie Weaver, Ph.D., director of the department of food and nutrition, at Purdue University, West Lafayette, Ind.

A recent analysis of data collected by the National Health and Nutrition Examination Survey (NHANES) during 1988-1994 and 2001-2004 even suggests that an epidemic of vitamin D deficiency may have hit the United States. A comparison of serum vitamin D levels from these two periods showed that the prevalence of vitamin D insufficiency, defined as a serum level of less than 10 ng/mL, jumped from 2% in 1988-1994 to 6% in 2001-2004, Dr. Adit A. Ginde from the University of Colorado in Denver and his associates reported (Arch. Intern. Med. 2009;169:626-32).

In addition to vitamin D's well-known effects on bone metabolism, levels in the range of 1,000 IU per day have been associated with good outcomes in recent controlled and epidemiologic trials that examined risks for falls in the elderly and people with type 2 diabetes.

Also, 1,000 IU is well below the 2,000- IU upper limit of vitamin D mentioned in the existing guidelines, Dr. Weaver said at Scripps Health: Natural Supplements: An Evidence-Based Update.

The IOM is not likely to recommend that people spend a lot more time in the sun as a way of increasing vitamin D, advice which would run counter to skin cancer prevention efforts.

Further, “you cannot eat enough vitamin D-containing foods to get anywhere near 1,000 IU of vitamin D per day,” said Dr. Weaver, who served on the IOM committee for the current guidelines.

Any substantive increase in recommended daily vitamin D intake will probably mean a call for supplementation. However, the IOM has been reluctant to make nutrient recommendations that exceed what an individual can reasonably obtain from ordinary food consumption.

“Subsequent research has shown that levels much higher than 2,000 per day showed no evidence of harm. So the upper limits will likely change along with the new intake recommendations,” Dr. Weaver said. “Until the upper limits go up, the ability to fortify foods is hindered. Higher upper limits will engender bolder efforts and greater fortification.”

Osteoporosis prevention is the strongest rationale for increasing vitamin D intake, she added, given the epidemiologic correlations between low vitamin D status and increased risk of fractures in the elderly. Research showed that daily supplementation with 700 IU vitamin D and 500 mg calcium reduced the 3-year rate of first nonvertebral fractures by 5.5%, compared with placebo, in a cohort of 176 men and 213 women aged over 65 (N. Engl. J. Med. 1997;337:670-6).

Dr. Weaver cited a National Health and Nutrition Examination Survey III data analysis showing significant and positive improvements in bone mineral density in a cohort of adults aged 50 years and older as serum vitamin D increased from 20 nmol/L to 40 nmol/L. The improvements continued to be noted at values over 80 nmol/L. Similar patterns were observed for various ethnicities (Am. J. Med. 2004;116:634-9).

The same researchers published a meta-analysis of six large population studies showing that the relative risk of all bone fractures starts to decline when daily vitamin D intake increases to roughly 450 IU per day (J. Steroid Biochem. Mol. Biol. 2007;103:614). “You really need to get up around 700 IU per day to achieve the lowest relative risk of hip fractures in this meta-analysis,” said Dr. Weaver.

Although vitamin D plays a role in bone metabolism, its fracture-reducing impact may also have something to do with its effects on neuromuscular function and overall health status. Observational data from the NHANES III database showed that those with the highest vitamin D serum levels had the shortest times on the sit-to-stand test in a large cohort of people aged 60-90 years (Am. J. Clin. Nutr. 2004;80:752-8).

Further, a study of 122 Swiss women in a geriatric hospital showed a 49% reduction in incidence of falls among the women taking 800 IU vitamin D plus 1,200 mg calcium for 3 months, compared with those taking calcium alone (J. Bone Miner. Res. 2003;18:343-51.)

But bone health is only one aspect of the vitamin D story, said Dr. Weaver. Low vitamin D level is associated with increased risk of cardiovascular disease and, possibly, type 2 diabetes.

A Framingham Offspring study found a hazard ratio of 1.62 for incident cardiovascular events during a 7-year period for subjects with serum vitamin D levels less than 15 nmol/L. The observed effect was largely attributable to the 40% of the total cohort who were hypertensive at baseline. In this subgroup, the hazard ratio was 2.13 for those deficient in vitamin D versus those who were not. The authors noted that vitamin D receptors are plentiful in vascular smooth muscle, endothelium, and cardiomyocytes (Circulation 2008;117:503-11).

According to Dr. Weaver, the emerging story is vitamin D's role in glucose metabolism and its potential for lowering the risk for type 2 diabetes.

A new Framingham Offspring study involving 808 nondiabetic individuals showed a strong inverse correlation between serum vitamin D levels and fasting plasma glucose and fasting insulin, as well as homeostatic model assessment (HOMA) for insulin resistance, after researchers controlled for age, gender, body mass index, waist circumference, and smoking. Compared with those in the lowest vitamin D tertile, those in the highest tertile had a 1.6% lower concentration of fasting glucose and a 9.8% lower concentration of fasting insulin, translating into a 12.7% lower HOMA-IR score.

Vitamin D showed a positive correlation with insulin sensitivity, plasma adiponectin, and HDL cholesterol (J. Nutr. 2009;139:329-34).

This work builds on prior studies at the division of endocrinology, diabetes, and metabolism at Tufts University, Boston, that showed consistent correlations between low vitamin D status and metabolic syndrome, insulin resistance, and frank diabetes.

In an analysis of data on nearly 84,000 women in the Nurses Health Study, the Tufts researchers found a 13% reduced relative risk of type 2 diabetes in the women taking the highest versus lowest amounts of supplemental vitamin D. Supplementation with 1,200 mg calcium or more and 800 IU vitamin D or more was associated with a 33% lower risk of type 2 diabetes, compared with an intake of less than 600 mg calcium and 400 IU vitamin D (Diabetes Care 2006;29:650-6).

“This is a very interesting story, to be watched closely,” Dr. Weaver concluded.

2 posted on 04/30/2009 10:56:47 PM PDT by Smokin' Joe (How often God must weep at humans' folly. Stand fast. God knows what He is doing.)

I don't have the reference handy, but a German doctor who routinely treated his hospital ward with 2,000 IU of vitamin D daily observed that none of them contracted the flu during a hospital wide outbreak. That observation suggested that susceptibility to flu during winter might be a consequence of low vitamin D levels from restricted exposure to sunlight.

Interesting...
I just checked my own regimen and I’ve been taking 800/day.

I remember a similar story from a shrink, IIRC.

Funny. Seems that even though many times there is (yet) no direct causative link between low vitamin D levels and certain maladies, it seems that over and over when they study the vitamin D levels of groups of people afflicted with certain diseases, they end up showing deficiencies.

9 posted on 05/01/2009 12:06:55 AM PDT by pandoraou812 (elected officials should be required to pass drug, alcohol & dementia testing)

10 posted on 05/01/2009 12:08:46 AM PDT by pandoraou812 (elected officials should be required to pass drug, alcohol & dementia testing)

Not a German, American. Dr. J. J. Cannell. Epidemic Influenza And Vitamin D.

He also runs this web site which has fascinating information, particularly his views on Vitamin D and autism:

Vitamin D Council

Article on autism

I read his arguments and immediately went out and bought some Vitamin D. Now taking 5000 IU/day. At first sign of flu, I plan to take the pharmacological dose of 2000 IU/kg body weight/day.

Two years ago I read about a study that indicated a corelation between vitamin d deficiency and colds or flu.

So I started taking calcium and vitamin d supplements, and for the first time, I did not get a cold or flu during the winter. This worked again last winter too.

I was exposed to the flu, and the doctor had me take an antiviral during one of those winters.

12 posted on 05/01/2009 1:15:55 AM PDT by greeneyes (Moderation in defense of your country is NO virtue. Let Freedom Ring.)

The same with ZINC; I have been taking 50 mg. a day for over 12 years and have only been sick once.

I take 800-1200 I.U. Vitamin A a day.

Thanks for the link to a great article!

Maria

15 posted on 05/01/2009 5:58:22 AM PDT by Coldwater Creek ("There is no insanity greater than electing a pathological Narcissist as president.")

I read his arguments and immediately went out and bought some Vitamin D. Now taking 5000 IU/day. At first sign of flu, I plan to take the pharmacological dose of 2000 IU/kg body weight/day.

I'm taking 2000 IU/day. That pharmacological dose sounds excessively high.

I did see Dr. Cannell's name when I searched after my prior post.

The pharma dose is only taken for a day or two at the onset of flu-like symptoms.

That’s great. My multiple vitamin has 2500 iu of vitamin A, and 100% RDV for most other vitamins and minerals including zinc.

I really do believe that eating healthy is the best thing people can do to enable their body to keep itself healthy.

Thanks for the tip.

19 posted on 05/02/2009 5:17:40 PM PDT by greeneyes (Moderation in defense of your country is NO virtue. Let Freedom Ring.)

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