Vitamine D en mensen met taaislijmziekte*
Uit een Amerikaanse studie blijkt dat veel mensen en zeker kinderen met taaislijmziekte een flink tekort hebben aan
vitamine D en dat de bestaande geadviseerde hoeveelheden veel te laag zijn. Hierdoor hebben deze mensen een hoog risico op botontkalking en zelfs rachitis. 83% heeft te lage bloedwaarden vitamine D (< 30 ng/ml) in de winter en 41% tijdens de zomer. De geadviseerde hoeveelheden vitamine D bij deze mensen met lage bloedwaarden is twee maanden lang een wekelijkse dosis van 1.250 mcg. Uit de studie blijkt dat zelfs twee tot drie keer deze dosering nodig kan zijn om goede bloedwaarden te bewerkstelligen. Voor slechts 1/3 van de patiënten bleek de geadviseerde dosis van 1.250 mcg voldoende te zijn. Meer onderzoek is nodig om te kijken welke dosering nu echt effectief is.
Zeker is dat patiënten met taaislijmziekte regelmatig hun bloedwaarden vitamine
D moeten laten controleren.
Children With Cystic Fibrosis Not Well Covered By Guidelines For Vitamin D Needs
Existing recommendations for treating vitamin D deficiency in children with cystic fibrosis (CF) are too low to cover the serious need, leaving most at high risk for bone loss and rickets, according to researchers at Johns Hopkins Children's Center.
In results of their investigation, published in The Journal of Pediatrics, the Johns Hopkins team found that nearly half of the 262 children with CF in the study were vitamin D deficient, and the majority of these remained persistently so, despite getting restorative doses equal to or higher than the recommendations set by the Cystic Fibrosis Foundation.
As a result of the findings, Hopkins already has amended its treatment protocol and now treats both adult and pediatric CF patients who have vitamin D deficiency with 50,000 IU daily for four weeks. Growing children with CF are especially vulnerable to vitamin D deficiency because a hallmark of their condition is poor absorption of nutrients and malnutrition. CF, a genetic disorder, is marked by the body's inability to transport chloride in and out of cells, causing mild to life-threatening complications, including recurrent and severe lung infections and delayed
growth.
The Cystic Fibrosis Foundation defines vitamin D deficiency in patients as levels lower than 30 nanograms per milliliter and recommends that patients who are vitamin D deficient receive a weekly dose of 50,000 IU of ergocalciferol, a form of vitamin D.
"These findings are a big wake-up call not only because they show that many children with CF are lacking vitamin D, but also because the deficiency persists even in those children who are treated with weekly doses twice or three times as high as the current recommendations," says Hopkins Children's lung specialist Deanna Green, M.D., who led the research. "Clearly there is an urgent need to find more effective ways to restore healthy vitamin D
levels."
In the meantime, investigators say, doctors caring for patients with CF should think about increasing the vitamin D intake beyond the current recommendations in those who are vitamin D deficient. They should also check vitamin D levels at least once a year in all CF patients and more frequently in those with abnormally low
levels.
In the current study of CF patients treated at Hopkins Children's between 2003 and 2006, investigators found that 86 percent were vitamin D deficient in 2003, 50 percent were deficient in 2004, 54 percent were deficient in 2005, and 46 percent were deficient in 2006.
Comparing different weekly intakes of ergocalciferol, the Hopkins team found that the currently recommended 50,000 IU per week for eight weeks was effective in only 33 percent of the patients with vitamin D deficiency, while increasing the therapy to twice a week was effective in 26 percent of patients. Delivering the same dose three times a week corrected the deficiency in just 43 percent of children.
Vitamin D levels appeared to follow fluctuations in seasonal sun exposure, dropping sharply in the fall and winter and peaking during spring and summer.
Vitamin D deficiency was worst during the fall, with 83 percent of patients testing deficient, while only 41 percent were vitamin D deficient in the summer. Sun exposure is critical for vitamin D synthesis and production. Some doctors recommend sun exposure twice a week for up to 30 minutes at a time, but the debate is ongoing because sun exposure without protection increases the risk of skin cancer.
"Clearly we haven't established an optimal dose for treating vitamin D deficiency and more research is needed to do so," says senior researcher Peter Mogayzel, M.D. Ph.D., director of Hopkins Children's Cystic Fibrosis Center. "But what we know for sure is that the current recommendations are too low, and doctors should treat their patients with vitamin D deficiencies more
aggressively,"
New therapies and earlier diagnosis have led to more and more CF patients living longer and well into adulthood, which means that vitamin D deficiency will be increasingly important for CF patients as they age.
"It is a testament to the advances we've made in treating CF, but as more and more patients survive and live longer, they will begin to face chronic conditions usually seen in healthy adults," Mogayzel says. "If we do not treat vitamin D deficiency early on, bone disease and osteoporosis will be increasingly a problem in the aging CF
population."
The findings come on the heels of another Hopkins study showing that low levels of vitamin D increased the overall risk of death by 26 percent in the general population.
Other investigators in the study: Kathryn Carson, Sc.M.; Amanda Leonard, M.P.H. R.D., C.D.E.; Erin Davis, R.D.; Beryl Rosenstein, M.D.; and Pamela Zeitlin, M.D. Ph.D., all of Hopkins.
Johns Hopkins Medicine
901 S Bond St., Ste. 550
Baltimore, MD 21231
United States
http://www.hopkinsmedicine.org (December
2008)
