According to a new study teenagers who have an unhealthy and unbalanced diet may be more prone to respiratory problems such as asthma.
The study suggests that a low dietary intake of certain nutrients increases the likelihood of respiratory symptoms such as asthma, and this is especially so in teenagers who smoke.
The researchers also say a lack of such nutrients may also affect lower lung function.
Lead study author Dr. Jane Burns of Harvard School of Public Health, says this study along with other research, suggests that higher intakes of antioxidant and anti-inflammatory micronutrients are linked to fewer reports of cough, respiratory infections, and less severe asthma-related symptoms.
Dr. Burns says teenagers who have low dietary intakes of fruit, vitamin E, and omega-3 fatty acids are at greater risk of having asthma; she says the study highlights the importance of a balanced diet, composed of whole foods.
For the study Dr. Burns and her colleagues from Health Canada, Brigham and Women's Hospital, and the Environmental Protection Agency (EPA) looked at 12th-grade students from 12 communities around the U.S. and Canada.
In order to examine the associations of low dietary nutrient intake with low pulmonary function and respiratory symptoms over the duration 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 says the teenage years were chosen as the focus because it is the ideal time at which to test lung capacity and compare eating habits as most have reached their adult physical stature and lung growth closely parallels this growth.
Burns says although the diet survey targeted eating habits only during the past year, it did give an indication of the teenagers' past diet and it is suspected that current respiratory health may also be a reflection of diet during childhood.
In the study most of the teenagers were white, one third were overweight, and 72% did not consume multivitamins, while almost 25% reported smoking on a daily basis.
The study revealed 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.
The results showed that low dietary intakes of fruit, vitamins C and E, and omega-3 fatty acids were linked to 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.
Dr. Burns says it is important to remember that diet can have a significant impact on teenagers’ respiratory health and they need to be encouraged to make healthy eating a part of their daily routine, and understand that smoking is bad for the health.
The researchers emphasise that fresh fruits make convenient healthy snacks and advocate the preparation of a simple, daily family meal, as a method to promote both communication and good nutrition.
The American College of Chest Physicians supports that view and says parents and doctors must work together to monitor and maintain healthy diets and lifestyles for children of all ages.
According to Dr. Burns vitamin supplements can help teens meet their daily recommended levels and even relatively low levels of omega-3 fatty acids appeared to protect teens from respiratory symptoms.
But she believes there are benefits not yet fully understood from eating whole foods such as fruits, vegetables and fish, and omega-3s are also found in walnuts and flaxseed oil as well as some green vegetables.
The study is published in the July issue of CHEST, the journal of the American College of Chest Physicians (ACCP).