Low Vitamin A and C Levels May Boost Risk of Asthma
Lee Swanson Research Update
A review of 40 studies and 30 years of research suggests that low dietary intake of vitamins A and C may increase the risk of developing asthma. Low blood levels of vitamin C and lower dietary intake of vitamin C-containing foods were associated with a 12% heightened risk of asthma.
"Our findings from [the current] systematic review and meta-analysis indicate that low levels of vitamin C intake, and to a lesser extent vitamin A, are consistently associated with asthma risk to a degree that, if causal, would be sufficient to be clinically relevant," wrote the researchers, led by Jo Leonardi-Bee from the University of Nottingham in the U.K.
According to the American Lung Association, almost 20 million Americans suffer from asthma. The condition is reported to be responsible for over 14 million lost school days in children, while the annual economic cost of asthma is said to be over $16.1 billion.
Leonardi-Bee and co-workers note that the new findings are plausible since vitamins A and C have well-known anti-inflammatory and antioxidant actions.
The Nottingham researchers searched the literature for peer reviewed research and abstracts of conference proceedings on asthma and wheezing and vitamin intakes. A total of 40 studies were identified.
The pooled results showed that vitamin A dietary intakes were significantly lower among asthmatics than in those who had not been diagnosed with the disease. The average intake of 182 mcg of the vitamin was equivalent to between 25% and 33% of the RDI. The researchers noted that people with severe asthma had significantly lower vitamin A intakes than people with mild asthma.
When Leonardi-Bee and co-workers considered vitamin C they found low blood levels of the vitamin and low dietary intakes of vitamin C foods were associated with a 12% increase in the risk of asthma.
Thorax Published online ahead of print.
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