In testing older patients' blood vitamin D levels, there's uncertainty about where the dividing line falls between enough and not enough. The threshold amount has become controversial as several scientific societies set different targets.
To help resolve this debate, University of Washington researchers conducted an observational study. They wanted to learn how much vitamin D must be circulating in the blood to lower the risk of a major medical event. This category included heart attack, hip fracture, diagnosis of cancer, or death.
Their findings are reported today, May 1, in the Annals of Internal Medicine. Dr. Ian de Boer, assistant professor of medicine in the Division of Nephrology and a member of the Kidney Research Institute, led the project. He also holds an appointment in the Department of Epidemiology, UW School of Public Health.
Vitamin D is measured in the blood as 25-hydroxy-vitamin D, abbreviated 25(OH)D.
The researchers tested 25(OH)D concentrations from a biorepository of blood samples of 1,621 Caucasian adults. These adults had enrolled in the early 1990s in the Cardiovascular Health Study, originally designed to look at risk factors and progression of heart disease in people age 65 and over. The participants lived in one of four areas in the United States: Forsyth County, North Carolina; Sacramento, County, California; Washington County, Maryland; and Philadelphia, Pennsylvania.
Over about an 11-year follow-up, researchers looked at the association between each individual's 25(OH)D test results and the time that a first defining medical event occurred. Among the participants, 1,018 had such an event. There were 137 hip fractures, 186 heart attacks (myocardial infarctions), 335 incidences of cancer, and 360 deaths.
Through their statistical analysis, the researchers concluded that the risk of these disease events rose when the concentration of 25(OH)D fell below 20 ng/milliliter or 50 nmol/liter.
"Our results," de Boer said, "lend support to the threshold level recently recommended by the Institute of Medicine, a national, independent government advisory group."
He added, "This target level for adults is considerably lower than that set by other expert panels.'
His research team also found that the association of low 25(OH)D blood concentrations with risk of major disease events varied with the season. Because people soak up most of their Vitamin D from the sun, their levels run highest in the summer and lowest in the winter. Levels in autumn are generally above those in spring.
"In evaluating health risk," the researchers concluded, "Season-specific targets for 25(OH)D blood concentration may be more appropriate than a static target when evaluating patients health risk."
Future research in this area, de Boer said, will require clinical trials. Researcher will look, for example, at the health effects of attempts to raise 25(OH)D in patients whose levels fall below the target. Interventions might include supplements, dietary changes and increasing outdoor activity."Sun exposure is tricky," de Boer said, "because people have to protect themselves from skin cancer and other sun damage." Sunscreen blocks the UVB waves responsible for producing Vitamin D. Food sources for Vitamin D are milk, fortified juice and cereal and oily fish like salmon, mackerel, cod and herring.
In addition to de Boer, other UW authors of the research paper, "Serum 25-hydroxy vitamin D concentrations and risk of major clinical disease events in a community-based population" are Gregory Levin and Mary L. Biggs, Biostatistics; Cassianne Robinson-Cohen, Epidemiology; Andy Hoofnagle, Laboratory Medicine; David Siscovick, Cardiovascular Health Unit and Medicine and Epidemiology; and Bryan Kestenbaum, Nephrology, Kidney Research Institute and Epidemiology.
The research was funded by grants from the National Institutes of Health, including the National Heart, Lung and Blood Institute, the National Institute of Neurological Disorders and Stroke, the National Institute on Aging, and the National Institute of Diabetes and Kidney Disease.
Leila Gray | EurekAlert!
Team discovers how bacteria exploit a chink in the body's armor
20.01.2017 | University of Illinois at Urbana-Champaign
Rabies viruses reveal wiring in transparent brains
19.01.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences