Vitamin D Research In Brief

Insufficiency common with osteoporosis: Vitamin D insufficiency is "remarkably common" in pediatric patients with primary and secondary osteopenia or osteoporosis, according to a study in the June Pediatrics journal. Researchers led by Sasigarn A. Bowden, of the endocrinology and nephrology divisions at Columbus (Ohio) Children's Hospital/Ohio State University College of Medicine, monitored serum 25-hydroxyvitamin D, 1,25 dihydroxyvitamin D - the physically active form of the vitamin - parathyroid hormone and other bone markers, as well as bone mineral density, in 85 pediatric patients with primary osteoporosis and secondary osteopenia. They found vitamin D insufficiency - defined as serum 25-OH D at less than 30 nanograms per milliliter - in 80 percent of the patients, while overt vitamin D deficiency - 25-OH D at less than 10 ng/ml - was present in 3.5 percent. The researchers also found an inverse relationship between 25-OH D and parathyroid hormone levels, which suggests a "physiologic impact of insufficient vitamin D levels that may contribute to low bone mass or worsen the primary bone disease." Bowden et al. suggest monitoring and supplementation with vitamin D should be a priority....

Suboptimal levels: A study in the June Archives of Pediatrics and Adolescent Medicine shows vitamin D deficiency in 12.1 percent of the healthy infants and toddlers who participated, while 40 percent had suboptimal levels. Catherine M. Gordon, of the divisions of Adolescent Medicine and Endocrinology at Children's Hospital Boston and her colleagues examined 380 healthy infants and toddlers who came for routine visits. Among the vitamin D-deficient children, one-third had evidence of demineralization. Also, breast-fed infants without supplementation were deficient, according to the researchers. "Unexpectedly, we found that skin pigmentation, sun exposure and sunscreen use were not predictors of 25-OH D concentration or vitamin D deficiency, as was hypothesized," they say. The researchers say the data differ from their previous study of adolescents and infants or young children and other similar research that found dark skin pigmentation was associated with vitamin D deficiency. Even though the APAM study included 233 African-American children, skin pigmentation was not identified as a risk factor for deficiency. The researchers hypothesize this may be because infants often are dressed in more layers of clothing than older children....

Increase risk of prostate cancer?: Vitamin D does not decrease the risk of prostate cancer, and in higher levels may be associated with an increased risk of aggressive disease, according to a study in the April Journal of the National Cancer Institute. Jiyoung Ahn, of the National Cancer Institute's Division of Cancer Epidemiology and Genetics in Bethesda, Md., led the study examining 749 case patients with incident prostate cancer who were diagnosed one to eight years after blood draw and 781 control subjects who were frequency matched by age and year of cohort entry and time since initial screening. The study excluded subjects with prostate cancer diagnosed within the first year of follow-up after their initial screening. Ahn's team found the rates of aggressive prostate cancer for increasing quintiles of serum 25-OH D were 406, 479, 780, 633, and 544 per 100,000 person-years. The researchers found no statistically significant trend in overall prostate cancer risk with increased serum 25-OH D levels, but concentrations greater than the lowest quintile of serum were associated with increased risk of aggressive - clinical stage III or IV - disease. The researchers say the vitamin D "signaling pathway interacts in a complex fashion with other signaling pathways, and their downstream effect on cellular differentiation, proliferation and apoptosis are not entirely understood," warranting further studies on the underlying mechanisms between the vitamin and aggressive prostate cancer....

D3 safe at 2,000 IUs: Vitamin D3 at daily doses equal to 2,000 IU for one year is safe in adolescents and results in desirable vitamin D levels, according to a Journal of Clinical Endocrine Metabolism study published online April 29. According to researchers led by Joyce Maalouf, of the American University of Beirut School of Medicine's Calcium Metabolism and Osteoporosis Program, although symptoms of vitamin D deficiency are "prevalent in children and adolescents worldwide the recommended daily allowance of 200 IU is not sufficient to remedy this universal problem." D3 is the animal form of the vitamin made with cholecalciferol, while D2 is the plant form made with ergocalciferol. To test the safety of vitamin D at higher doses, the researchers had 25 subjects randomly receive either placebo or vitamin D3 doses of 14,000 IU per week for eight weeks to study short-term safety. In addition, 340 subjects randomly received either placebo or vitamin D3 for one year. The researchers found in both the short- and long-term studies, mean serum calcium and 1,25-hydroxyvitamin D levels did not change in any group. Mean 25-OH D concentrations increased from 44 to 54 ng/ml in the treated groups in the short-term study; in the long-term study, the concentrations increased from 15 to 19 ng/ml in subjects receiving 1,400 IU per week and from 15 to 36 ng/ml in the group receiving 14,000 IU per week....