Low vitamin intake tied to asthma risk

May 17, 2006 - 3:11PM

People with symptomatic asthma eat less fruit and consume less vitamin C and manganese than people who don't have the disease, a new study shows.

The findings suggest that "diet may be a potentially modifiable risk factor for the development of asthma," Dr N.J. Wareham of the Medical Research Council in Cambridge, UK and colleagues write in the medical journal Thorax.

Several antioxidant nutrients have been linked to reduced asthma risk, Wareham and his team note, but it is not clear whether each of these nutrients plays a role in reducing risk or if they instead represent an overall healthier lifestyle.

To investigate, they compared the diets of 515 adults who had been diagnosed with asthma and 515 "controls" - similar adults without the disease. All reported their food intake over a one-week period. One-third of the asthma patients reported having had no symptoms in the past 12 months.

Asthma patients ate an average of 132.1 grams of fruit daily, compared to 149.1 grams for healthy controls. Those who ate at least 46.3 grams of citrus daily had about half the risk of having asthma with symptoms compared to those who ate no citrus fruit at all. Lower intake of both vitamin C and manganese were tied to an increased risk of symptomatic asthma, while symptomatic asthma patients had significantly lower levels of plasma vitamin C than healthy controls.

The findings don't support the idea that overall healthy lifestyle plays a role in asthma risk, the researchers note, because both asthma patients and healthy controls consumed the same amounts of calories and fat and showed similar levels of physical activity, education, and likelihood of having smoked in the past.

While it appears clear that lower vitamin C levels among asthma patients are due to lower fruit intake, it isn't clear what dietary factors contribute to reduced manganese consumption, they add. Controls did not eat more cereals and grains - both of which are rich in manganese - than asthma patients, although they did drink more tea, which is another key source of the antioxidant nutrient.

The researchers conclude: "These findings may be of public health importance in understanding the apparent increase in the prevalence of asthma."

- Reuters

SOURCE: Thorax, May 2006.
