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Message to Teens: No Fruit? No Fish? Say Hello to Asthma and Bronchitis

Posted on: Monday, 9 July 2007, 21:19 CDT

By HELEN BRANSWELL

TORONTO (CP) - Teens who turn up their noses to fruit and fish may be undermining their lung health, new research released Monday suggests.

The work, based on the study of 2,112 American and Canadian teenagers, found an association between good lung function and levels of dietary intake of fruit and fish rich in omega 3 fatty acids.

Teens who ate less of these foods had higher rates of asthma, wheezing and symptoms of chronic bronchitis such as cough and phlegm, said the researchers, from the Harvard School of Public Health and Health Canada.

"The walk-away (message) is that . . . if your diet is generally lacking in these types of things your risk of having and continuing to have symptoms associated with chronic bronchitis and asthma are increased," said Mark Raizenne, director of Health Canada's sustainable development division.

"Even in adolescence if you're starting to have poor nutrition and you're starting to have some of these poor habits, you will probably start having the symptoms that are associated with long-term respiratory problems."

"And it starts that early. Don't be surprised in your 20s and 30s if you had those problems earlier on."

Raizenne was formerly in Health Canada's health effects research section; he collaborated on this study while he was in that division.

The research team gathered information on diet, smoking, exercise levels and medications from selected Grade 12 students in 13 U.S. and Canadian communities. The Canadian teens who took part were from Leamington and Egbert, Ont., and Yorktown, Sask.

They also asked the teens whether they had ever been diagnosed with asthma or related conditions and conducted lung function testing on them.

Lead author Jane Burns, with Harvard's School of Public Health, said teenagers who reported eating a quarter or less of a serving of fruit a day were 36 per cent more likely to report having chronic bronchitis, chronic cough and phlegm. A quarter of a serving of fruit a day is the equivalent of about two pieces of fruit a week.

Those who had low intake of omega 3 fatty acid-rich foods were 37 per cent more likely to have increased levels of these chronic bronchitic symptoms.

Health Canada's new Canada Food Guide recommends teenage girls consume seven fruits and vegetables a day and recommends teenage boys consume eight. But the researchers found that 86 per cent of the teenagers reported they did not eat even five servings daily of these important foods.

The study was an observational one, meaning the researchers could only observe what happened to subjects who followed a certain type of behaviour - in this case, a type of diet.

Such studies can only point out what's called an association between a behaviour and an outcome. They cannot prove cause and effect. To do that the researchers would have had to randomly select some teens to eat high fruit diets and others to eat few fruits - a research proposal unlikely to get ethics board approval.

Teresa To, head of child health evaluative sciences at Toronto's Hospital for Sick Children, concurred that this study can't prove fruit consumption boosts lung function. But she said the findings point towards a link.

"It may not be the last thing that we should do but this certainly is a first step for us to look deeper into the role of dietary intake and respiratory health," To said, noting she was concerned about the level of fruit and vegetables the studied teens reported eating.

Burns said the theory that these kinds of foods contribute to good lung health makes sense from a biological point of view. Other studies, in adults, have shown lung function and diet are linked, she said. And still others have shown that increasing intake of vitamin C can raise the levels of vitamin C in the fluid that protects the respiratory tract.

"Mechanistically, there's definitely a solid role that antioxidants play in respiratory health," she said from Boston.

Interestingly, this study didn't find vegetable consumption was protective against asthma and related illnesses. But Burns was quick to suggest other studies have shown that link. She also suggested the effect of antioxidant rich vegetables may have been diluted by the fact that the study included a broad spectrum of vegetables, some of which - like potatoes - are known to contain much lower levels of these important nutrients.

"It's not that I don't think vegetables matter. It's just that the way we looked at them, we didn't see an association in this group of teens," Burns said.

Source: Canadian Press

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