Vitamine D tegen griep en astma*
Uit twee studies blijkt dat voldoende vitamine D belangrijk is ter voorkoming van
griep en astma-aanvallen. Uit de eerste, kleine Amerikaanse studie onder kinderen blijkt dat 86% van de kinderen met astma duidelijk te lage bloedwaarden vitamine D hebben dit in tegenstelling tot gezonde kinderen waarvan slechts 19% een tekort heeft. Uit de tweede, een kleine Japanse studie onder kinderen blijkt dat goede bloedwaarden vitamine D belangrijk in het voorkomen van griep en de kans op een astma-aanval. De kinderen in deze studie kregen dagelijks of 30 mcg vitamine D3 of een placebo. In de vier (winter)maanden bleek dat kinderen in de
vitamine D-groep 58% minder kans hadden op het krijgen van griep. Zes keer meer kinderen in de placebogroep dan in de vitamine D-groep kregen in die periode een astma-aanval. Het idee van deze studie was ontstaan als gevolg van een eerder onderzoek naar vitamine D en osteoporose waaruit o.m. gebleken was dat zij die regelmatig vitamine D innamen wel drie keer minder kans hadden op het krijgen van een
verkoudheid of griep.
Vitamin D helps fend off flu, asthma attacks: study
In a study of Japanese schoolchildren, vitamin D supplements taken during the winter and early spring helped prevent seasonal flu and asthma attacks.
The idea for the study, study chief Dr. Mitsuyoshi Urashima, told Reuters Health, came from an earlier study looking at whether vitamin D could help prevent the bone-thinning disease osteoporosis. The researchers in that study noticed that people taking vitamin D were three times less likely to report cold and flu symptoms.
This led Urashima, of Jikei University School of Medicine, Tokyo, and colleagues to randomly assign a group of 6- to 15-year-old children to take vitamin D3 supplements (1,200 international units daily) or inactive placebo during a cold and flu season.
Vitamin D3, or cholecalciferol, is more readily absorbed by the body and more potent than vitamin D2, or ergocalciferol, the form often found in multivitamins.
During the study, conducted between December 2008 and March 2009, 31 of 167 children taking placebo caught influenza A, the most common form of the virus, compared with only 18 of 167 taking vitamin D.
The vitamin D group was 58 percent less likely to catch influenza A, the researchers report in the American Journal of Clinical Nutrition.
Vitamin D also appeared to suppress asthma attacks in children with a history of asthma. Two children taking vitamin D had asthma attacks during the study, compared to 12 children taking placebo. Urashima admitted to being a bit surprised by this finding and hopes to confirm it in a randomized trial targeting children with asthma.
Dr. Adit Ginde, of University of Colorado Denver School of Medicine, who was not involved in the study, told Reuters Health: "This is the first time a study has been done that rigorously shows that vitamin D supplementation can reduce a type of influenza in a dedicated clinical trial." Ginde and colleagues published a study a year ago showing that asthmatics with lower vitamin D levels were at five times the risk for colds and flu.
In the Japanese study, vitamin D supplementation did not prevent influenza type B, which tends to appear later in the flu season than the "A" flu variety.
Ginde said there is no solid explanation for why vitamin D prevented influenza A and not influenza B. "The immune system fights different viruses in different ways. This finding needs to be explored in more detail," Ginde said.
Based on the current study, giving kids vitamin D supplements during the winter may help reduce cases of influenza A, the researchers conclude. Urashima suggests that children could take 1,200 IU per day starting in September to prevent flu and asthma attacks during the flu season, but best for parents to check with their pediatrician first.
SOURCE: American Journal of Clinical Nutrition
Link Between Low Levels Of Vitamin D And Higher Rates Of Asthma In African American Children
Researchers at Children's National Medical Center have discovered that African American children with asthma in metropolitan Washington, DC, are significantly more likely to have low levels of vitamin D than healthy African American children. This study supports recent research that suggests vitamin D plays a greater role in the body than just keeping bones healthy. Vitamin D deficiency has been recently linked to a variety of non-bone related diseases including depression, autoimmune disorders, and now asthma.
"It's been well-documented that as a group, African Americans are more likely than other racial groups to have low levels of vitamin D," said Robert Freishtat, MD, MPH, an emergency medicine physician and lead author on the study. "But we were shocked to see that almost all of the African American children with asthma that we tested had low vitamin D levels. After adjusting for differences in age, weight, and the time of year of the testing, the odds of these kids with asthma being vitamin D deficient were nearly twenty times those of healthy
kids."
The study took a one-time measurement of vitamin D in the blood of 85 African American children with asthma, who were between 6 and 20 years old. Additionally, the researchers measured the vitamin D levels of 21 healthy African American children between the ages of 6 and 9 years of age. The research team found that 86 percent of the children in the study with asthma had insufficient levels of vitamin D, while only 19 percent of non-asthmatics had these low
levels.
These findings may mean that low vitamin D levels have more serious effects on a child's lung health than previously believed. Though more research is needed to establish definitively how vitamin D deficiency can contribute to asthma, parents can ensure that their children receive healthier amounts of vitamin D by following the current USDA guidelines for milk consumption and seeking a doctor's advice about
multivitamins.
"The District of Columbia has among the highest rates of pediatric asthma in the United States, and we're working to find out why," says Stephen Teach, MD, MPH, senior author of the study. "For African American kids with asthma, vitamin D testing and ensuring adequate vitamin D intake may need to become necessary steps in their primary care."
Source:
Jennifer Leischer
Children's National Medical Center (Mei 2010)
