You are working in a correctional setting and start a new assignment in administrative segregation (jail within a prison). Many inmate-patients serve months to years in this setting and receive 1 hour of yard time per day. Many simply hole up and never go outside. You wonder if these inmates' vitamin D levels are adequate.
What is an adequate serum vitamin D level, and what are the health sequelae, both medical and psychiatric, to low levels of vitamin D?
We first searched the Cochrane Database of Systematic Reviews (www.cochrane.org) and found no reviews on this topic. We then searched Medline, combining "vitamin D" and "deficiency or psych$." We also located a comprehensive Web site: www.vitamindcouncil.com.
To find out what constitutes adequate vitamin D levels and what the medical consequences of low levels are, we turned to a recent review article by Dr. Michael F. Holick (N. Engl. J. Med. 2007;357:266-81). To answer the psychiatric part of the question, we reviewed original articles obtained from the sources cited above.
Vitamin D from the skin and diet is hepatically converted to 25-hydroxyvitamin D (25-OH D), which is used to determine an individual's vitamin D status. The 25-OH D is converted in the kidneys by 25-OH D-1-hydroxylase to the active form 1,25-dihydroxyvitamin D (1,25-OH D). Renal production of 1,25-OH D is regulated by parathyroid hormone (PTH), calcium, and phosphorus levels. With the discovery that most cells in the body have vitamin D receptors, the varied functions of this vitamin have become better understood.
Levels of 25-OH D are inversely proportional to PTH until 25-OH D levels reach 30-40 ng/mL. (Currently, most laboratories define deficiency as a 25-OH D level less than 20 ng/mL.) Researchers have shown intestinal calcium absorption to increase by 45%-65% in women when 25-OH D levels went from 20 to 32 ng/mL. Others have shown that more than 50% of postmenopausal women with osteoporosis had 25-OH D levels of less than 30 ng/mL. One study showed maximum bone density in men and women when the 25-OH D level was 40 ng/mL or greater. At levels less than 30 ng/mL, there was an increase in PTH (which stimulates the production of osteoclasts).
Another study showed that 93% of 150 patients who presented with muscle aches and bone pain and had diagnoses such as fibromyalgia or chronic fatigue had 25-OH D levels less than 20 ng/mL. Pooled data from multiple studies have shown that giving elderly men and women vitamin [D.sub.3] (700-800 IU) and calcium (500-1000 mg per day, or sufficient to maintain 25-OH D levels above 40 ng/mL) significantly reduces the risk of hip and nonvertebral fractures.
Skeletal muscle has vitamin D receptors. Performance speed and proximal muscle strength (with a subsequent decrease in falls) has been shown to increase as 25-OH D levels rise to greater than 40 ng/mL. Brain, prostate, breast, colon, and immune tissue also have vitamin D receptors. Epidemiological studies have shown that 25-OH D levels of less than 20 ng/mL are associated with a 30%-50% increased risk of colon, prostate, and breast cancer.
A large cohort study (32,826 participants) showed an inverse association between 25-OH D and the odds ratio for colorectal cancer: The odds ratio was 1.0 at 16.2 ng/mL and 0.53 at 39.9 ng/mL. Data for 980 women showed that the highest level of vitamin D intake, compared with the lowest, was associated with a 50% lower risk of breast cancer. Other studies have shown a 41% lower risk of multiple sclerosis for the higher level when comparing 25-OH D levels of 44 ng/mL and 24 ng/mL. …