April 16, 2009

Low Vitamin A, C Levels May Raise Asthma Risk

New British research finds that a low intake of vitamins C and A could raise the risk of asthma. 

Researchers from Nottingham University reviewed 40 studies conducted over the past three decades, and found that those with low intakes of vitamin C had a 12% increased risk of asthma.

Although the increased risk for low intake of vitamin A was less clear, a significant association was nevertheless observed, researchers said.

The Medical Research Council and Asthma UK have both said more research is needed since there has been a lot of confusion over the link. 

"The jury is still out as to how exactly vitamin intake and asthma are related," said Leanne Male of Asthma UK during an interview with BBC News.

Previous studies have varied in their conclusions.

In the current study, researchers analyzed previous research published since 1980 involving both children and adults.  Although they discovered no link for vitamin E, the associations for A and C were significant, the researchers said.

The scientists concluded that low levels of vitamin C, raised the risk of asthma by 12%.  While they were unable to derive a precise figure on vitamin A, commonly found in eggs, cheese and oily fish, they noted that those with severe asthma consumed on average half of the recommended amounts of the vitamin.

"Our findings 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," said Dr. Jo Leonardi-Bee, the study's lead researcher.

It is now important to conduct larger-scale studies to verify the link and to determine if there was a direct causation between low vitamin intake and asthma, he added.

Experts also agree that more research is needed, but caution that other factors may also be at play.

"The data provided is interesting, but inconclusive," Medical Research Council nutritionist Glenys Jones told BBC News.

"There are many factors such as smoking, physical activity and socio-economic status that have not been taken into account."

"Therefore more research is required to investigate a causal relationship."

The study was published in the journal Thorax.


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