Vitamin A is a nutrient that helps the body build healthy skin, teeth, bones, and mucus membranes. It is also important for healthy eyes and night vision. Some studies have suggested that a shortage of vitamin A during early development may increase the risk that a child will have asthma. A recent study by scientists at Johns Hopkins University working with scientists in Nepal seems to disprove that belief.
Vitamin A is a fat-soluble vitamin, which means it travels through the body in fat globules. After traveling through the body in the bloodstream, they are stored in body tissues for future use. If vitamin intake is significantly higher than the amount needed, these vitamins can accumulate in the tissues until they reach toxic levels.
Vitamin A is not produced by the body. It must be brought into the body through the foods we eat. Vitamin A can be found in animal sources including eggs, meat, milk, dairy products, cod, and halibut fish oil. It can also be found in plants including bright yellow-orange fruit such as cantaloupe and pink grapefruit, vegetables including carrots, pumpkin, and sweet potatoes, and dark leafy vegetables including broccoli and spinach.
Among other functions, vitamin A helps support the health of the lining of the airways in the lungs and respiratory system. This lining acts as a barrier to keep bacteria and other harmful particles from entering the body and causing infection. Scientists also know that it is important for a pregnant woman to get enough vitamin A to support the development of her baby’s lungs.
This led some researchers to question whether a lack of vitamin A in young children could trigger the development of asthma later in life. The research team from John Hopkins worked with scientists in Nepal to study over 5,000 people living in a rural area in that country where malnutrition was common. They followed up on two earlier trials involving children. In one study, half of the children received vitamin A supplements during their pre-school years while half did not. In a second study, part of a group of pregnant women received vitamin A supplements during and after pregnancy while others in the group did not.
The research team followed up with the children 10 to 15 years later. They used questionnaires and spirometry tests which measure how much air the lungs can take in and release as well as how well the lungs are able to move oxygen into the blood. Their study found no difference in lung function between the children who received vitamin A supplements, either before or after birth, and those who received no supplements. The researchers concluded that although vitamin A deficiency does affect lung development in unborn babies, it does not lead to a higher risk of asthma later in life.
Sources:
Science Daily
National Institutes of Health Office of Dietary Supplements
Medline Plus: Vitamin A
Medicine Net
Medline Plus: Pulmonary Function Tests
Reviewed June 30, 2011
by Michele Blacksberg R.N.
Edited by Alison Stanton