According to a new study from Johns Hopkins University in the United States, vitamin D is able to protect overweight children against asthma caused by urban air pollution. Sunshine during the summer period is the main source of vitamin D, but due to our modern lifestyles, many people, including children, fail to get enough of the nutrient. This may have widespread consequences, as lack of vitamin D also increases the risk of overweight.
The number of overweight children is growing and childhood asthma is also on the rise. This is an unfortunate cocktail. According to the American Centers for Disease Control and Prevention, one in 12 children in the US has asthma. Moreover, asthma tends to affect children living in cities and minorities such as black children. The increased air pollution from sources such as cigarette smoke, cooking, candles, and incense burning is generally associated with respiratory challenges, including asthma symptoms and a higher number of visits to the hospital. According to Dr. Sonali Bose, who is the lead investigator behind the new study, asthma is a result of a deranged immune system. Earlier studies have demonstrated that vitamin D is able to protect against asthma by regulating the immune system or by functioning as an antioxidant.
Vitamin D deficiency is especially bad for overweight asthma patients
When the scientists from Johns Hopkins University initiated their study, they already knew that Afro-Americans and other minorities of color were more likely than others to lack vitamin D. This is because dark skin synthesizes less vitamin D than light skin. On the other hand, it protects against sunburns. The scientists also observed that asthma was more common among children, who were overweight and lived in cities. It seemed as if there was a link between low levels of vitamin D and asthma in these groups.
The new study included 120 schoolchildren from the Baltimore region. All children had asthma. A third of the children were overweight. The scientists studied the following three factors:
- Air pollution levels in their homes
- Blood levels of vitamin D
- Asthma symptoms
The children were evaluated at baseline and three times in the course of the following nine months. Overall, the scientists observed that low levels of vitamin D in the blood caused the overweight children to have more asthma symptoms due to indoor air pollution. On the other hand, having higher blood levels of vitamin D was associated with fewer asthma symptoms in overweight children from the most polluted homes.
What surprised the scientists the most was that vitamin D had the greatest effect on overweight children. This addresses a third factor, and that is the growing obesity epidemic. It is therefore necessary to take this into account when planning ways to prevent and treat asthma.
Their study is published in The Journal of Allergy and Clinical Immunology: In Practice.
How do children get more vitamin D?
According to Bose, we should focus more on making sure that exposed children get more vitamin D, because with increased levels of the nutrient in their blood they are more resistant towards various environmental challenges. One way to get more vitamin D is by getting more sun exposure. However, during the winter period, the sun sits too low in the sky to enable vitamin D synthesis in the skin. Another problem with urban living is that there is more shade because of the tall buildings and, as mentioned before, people with dark skin do not synthesize as much vitamin D in their skin in the first place.
Many children would benefit from spending more time in the sun during the summer period, as long as they avoid sunburns. Spending as little as half an hour in the sun raises vitamin D levels substantially more than taking a regular vitamin pill. There is also vitamin D in foods such as oily fish and eggs, but the amounts are very limited. It is advisable to take a vitamin D supplement during the winter period and/or as compensation for spending too much time indoors.
New views on asthma and treatment
The scientists behind the study way that we must focus a lot more on pollution, overweight, and lack of vitamin D as possible explanations to the increasing rate of asthma. Their research shows that there are many factors that should be taken into account when finding ways to prevent and treat the disease.
Intake level and the actual need for vitamin D
There is a lot of disagreement about the actual need for vitamin D, which depends on a number of factors and is even influenced by body weight and skin color. With regard to supplementation, EFSA has set the upper safe daily intake level at 25 micrograms for infants, 50 micrograms for children aged 1-10 years, and 100 micrograms for older children and adults (including pregnant and breastfeeding women). Vitamin D is a lipid-soluble vitamin, which we humans utilize the best when it is dispensed in some form of oil in soft gelatin capsules.
Vitamin D supplements can reduce serious asthma attacks
According to an earlier study that is published in the Cochrane Library, supplements of vitamin D taken in combination with regular asthma medicine can reduce by 50 percent the risk of serious asthma attacks and improve quality of life. Professor Adrian R. Martineau, who headed this study, views vitamin D as a designer drug because it strengthens the immune defense at the same time as suppressing undesirable inflammation.
Vitamin D deficiency increases the risk of overweight and asthma
As seen, vitamin D deficiencies are more common among overweight people, but science does still not fully understand why. A study from Baylor College of Medicine in Houston, Texas, suggests that the explanation can be found in the brain, from where vitamin D contributes to controlling body weight and blood sugar levels. A vitamin D deficiency is a problem, as it increases the risk of overweight and asthma at the same time.
Threshold levels in the blood
When measuring vitamin D levels in the blood, the official threshold level is 50 nmol per liter of blood, but many scientists find that this is too little and suggest as much as 75-100 nmol per liter for optimal disease prevention.
Bose S et al. Vitamin D status modifies the response to indoor particulate matter in obese urban children with asthma. The Journal of Allergy and Clinical Immunology: In Practice. February 2019
Adrian R Martineau et al. Vitamin D for the management of asthma. Cochrane Library 2016
Sisley SR et al. Hypothalamic Vitamin D Improves Glucose Homeostasis and Reduces Weight. Diabetes 2016
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