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Vitamin D – A Steroid Hormone, Anti-inflammatory


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The Sunshine Vitamin Controversy

What should normal values  be for calcium homeostasis?

My attention was drawn to Vitamin D several years ago when a review appeared in the journal Neurology, published by the Academy of Neurology, that linked low levels of Vitamin D to Multiple Sclerosis.  The article was unusual for its length and the breadth of research cited over several decades.  More recently, a Johns Hopkins article published “the most conclusive evidence to date” that Low Vitamin D Levels Pose Large Threat to Health.

New publications on Vitamin D seem to appear every week with the focus on levels of 25-hydroxyvitamin D, also written as 25(OH)D. Its half life in serum is ~ 10 days to 3 weeks.

The biologically active form 1,25-dihydroxyvitamin D, written as 1,25(OH)D²,  is made in the kidneys and has a much shorter serum half-life of ~ 4-6 hours, thus making it less useful as a serum marker for measuring.

Sources & Metabolism: Vitamin D is a fat soluble vitamin that’s absorbed in the small intestine from  foods such as egg yolks, fatty fish, fish liver oils, fortified milk, margarine, and cereals.  Bile salts are required for absorption.  Sunlight stimulates the skin to synthesize vitamin D, but exposure of hands and face as little as 15 minutes may not be sufficient and it is not as effective for everyone.  It won’t work in winter months, it won’t work for the aged, for those who have pigmented skin, and it won’t work for those who cover their skin.

Vitamin D Metabolism - click to enlarge

Vitamin D Metabolism

The Controversy –  How Do We Determine Normal Values?

Surprisingly, in a well designed multicenter study of healthy young Hawaiians in their 20’s who were exposed to at least 29 hours of sun per week, 51% were found to have vitamin D deficiency using the usual cut off of 30 ng/ml for normal.  This study from 2007 found the mean concentration of 31.6 ng/ml, and the highest of 62 ng/ml.  It raises the question whether

“it seems prudent to use this value [60 ng/ml] as an upper limit when prescribing vitamin D supplementation,”

rather than the generally published normal range of 30 to 80 ng/ml or even 100 ng/ml quoted in some labs.  This study is important in discussing the controversial question of what normal values should be for calcium homeostasis and reviews several possible explanations for inadequate production of D3 including genetic differences.

They note the highest reported values in “Nebraska outdoor workers… were between 81 and 84 ng/ml” but the assay system differed compared to theirs and results in a higher value.   Reviewing this study that was published in the Journal of Clinical Endocrinology & Metabolism has allowed me just now to readjust my own patient practice.

Laboratory Testing:  results can differ from one laboratory to another.  My hospital sends specimens to ARUP for testing, whereas Quest has acknowledged errors in laboratory testing and problems with standardization as reported by the New York Times here.

Function:  It is important for absorption of calcium and phosphorous from the small intestine, for bone health, osteoporosis, risk of falls, certain cancers(colon, breast, prostate), and possibly 6 to 7 years of longevity.  Deficiency of vitamin D is associated with suboptimal health and possibly increased pain; it is linked to infections, gum disease, hypertension, diabetes, coronary disease, neurological diseases such as Multiple Sclerosis, Parkinson’s Disease, dementia and Alzheimer’s Disease though it may not be causal. Its receptor is found all over the body including the brain.

I recommend this review by one of the best web resources at Memorial Sloan Kettering Cancer Center Herbs & Botanicals.

They quote a reference showing it reduces postmenopausal weight gain and “In adults with impaired fasting blood glucose, giving calcium and vitamin D reduced increases in plasma glucose and insulin resistance….”

It is the only vitamin that is a steroid hormone, and my interest increased on learning that it functions as an anti-inflammatory.  But as I tested blood levels for 25(OH) vitamin D and parathyroid hormone (PTH), I discovered more than 90% of my patients had vitamin D deficiency and a few had hyperparathyroidism.  There are four parathyroid glands next to the thyroid, and for some reason doctors have rarely tested their hormone levels.

***Persons with hyperparathyroidism should NOT take calcium or vitamin D.

It may lead to kidney stones and bone pain:  stones, bones and groans.***

Evidence for Optimizing Vitamin D Concentrations

On the other hand, if vitamin D is low, there is some evidence that replacement with vitamin D3 so that blood levels are in the high normal range, may help pain.  That is, it may raise the pain threshold and possibly have other benefits for health and longevity. It is desirable to avoid toxic levels of D as it causes hypercalcemia with depression, drowsiness, weakness, headache, polydipsia,  bone loss, and metastatic calcifications of many organs, soft tissues and blood vessels.  The generally quoted range of normal for 25(OH) vitamin D is 30 to 80, that varies with the lab.

great-western-divide-wp1

Doesn’t that photo of the Great Western Divide make you want to get outside into the sun?

Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes was reviewed by Heike Bischoff-Ferrari et al, in 2006,  though it has been superseded by much additional work since then.

To quote from their article:

This review summarizes the evidence for optimal serum  25(OH)D concentrations. The endpoint selection for this review was based the strongest evidence to date—ie, that from RCTs [randomized controlled trials], consistent evidence from prospective and cross-sectional epidemiologic studies, and strong mechanistic evidence or dose response relations.  BMD [bone mineral density], fracture prevention, lower-extremity function, falls, oral health, and colorectal cancer met these criteria. Weaker evidence exists of a beneficial effect of vitamin D on other diseases, including multiple sclerosis (15), tuberculosis (16), insulin resistance (17, 18), cancers other than colorectal (19 –22), osteoarthritis (23, 24), and hypertension (25–27), but these diseases are not considered here.

They did not review pain studies.  I would add that “weaker” evidence merely means that it must be confirmed by more studies, not that it excludes those conditions.  There is an epidemic of vitamin D deficiency in the country, and the incidence is very high in pain clinics as reported in several studies.

A new multi-center epidemiology study  “Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988-2004”  by Ginde, et al, in 2006,  “demonstrate a marked decrease in serum 25(OH)D levels from the 1988-1994 to the 2001-2004 NHANES data collections.”  And like others before them, they point out:

“Current recommendations for vitamin D supplementation are inadequate to address the growing epidemic of vitamin D insufficiency.”

Summary:

Make sure your doctor checks both your 25(OH)Vitamin D and parathyroid hormone level (PTH) – not thyroid – to determine if you have hyperparathyroidism or if you have normal or low vitamin D.  That will determine if you need replacement or if you should stop using calcium and D as it will cause kidney stones and calcium deposits on your bones leading to pain.

If vitamin D levels are low it may result in increased physical pain and may cause or aggravate many medical conditions.

If PTH levels are high indicating hyperparathyroidism it will cause new painful conditions.

Intake does vary with the patient, the season, the age, but the recommended daily allowance may perhaps be double what it is now.  It is unclear when the federal government will adjust that dosage.   As always, your physician’s recommendation will be based upon blood levels of 25(OH)D and PTH.

Do not make changes in your dosage without careful evaluation.

Could this possibly be one of the most important areas of research this century?

The material on this site is for informational purposes only, and

is not a substitute for medical advice, diagnosis or treatment provided by a qualified health care provider.

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