Teens, especially those who smoke, may be at an increased risk of respiratory symptoms such as asthma it they forego a healthy and balanced diet.
The finding comes from a study by a group of researchers from Harvard School of Public Health, Health Canada, Brigham and Women's Hospital, and the Environmental Protection Agency (EPA) led by Jane Burns, ScD, Harvard School of Public Health who found that teens whose diet doesn't contain sufficient amounts of fruit, vitamin E and omega-3 fatty acids are at greater risk of having asthma.
"Our study, as well as other research, suggests that higher intakes of antioxidant and anti-inflammatory micronutrients are associated with lower reports of cough, respiratory infections, and less severe asthma-related symptoms," said Jane Burns.
"Teenagers who have low dietary intakes of fruit, vitamin E, and omega-3 fatty acids are at greater risk of having asthma, emphasizing the importance of a balanced diet, composed of whole foods," she added.
As a part of the study the researchers observed 12th-grade students from 12 communities around the US and Canada and examined the associations of low dietary nutrient intake with low pulmonary function and respiratory symptoms.
Over the period of one school year, 2,112 students completed a standardized respiratory questionnaire and a dietary questionnaire. They also answered questions about medication use, smoking habits, and recent exercise, before participating in lung function testing.
Dr. Burns explained that the researchers focused on teens because it is the ideal age at which to test lung capacity and eating habits.
"During late adolescence, physical stature has, on average, been attained and lung growth closely parallels this growth. Therefore we were observing a time when lung function was close to its optimal capacity," she said.
The majority of adolescents in the study were white, one third was overweight, and 72 percent did not consume multivitamins. Also, nearly 25 percent reported smoking on a daily basis.
Researchers also found that at least one third of the students' diets were below the recommended levels of fruit, vegetable, vitamins A and E, beta-carotene, and omega-3 fatty acid intake.
"Vitamin supplements can help teens meet their daily recommended levels and surprisingly, even relatively low levels of omega-3 fatty acids appeared to protect teens from higher reported respiratory symptoms," said Dr. Burns.
Results showed that low dietary intakes of fruit, vitamins C and E, and omega-3 fatty acids were associated with decreased lung function and a greater risk of chronic bronchitic symptoms, wheeze, and asthma.
These risks were further increased among students with the lowest intakes and who also smoked.
"The most important thing to remember is that diet can have a significant impact on teens' respiratory health. I would encourage them to make healthy eating a part of their daily routine, and stress to them that smoking is bad," Dr Burns said.
Researchers emphasized that fresh fruits make for convenient snacks.
The study is published in the July issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians (ACCP).