Diets Short on Fruits, Fish Can Impair Teens’ Lung Function 

Key Point

Adolescents with low daily intake of fruit, n-3 fatty acids, and vitamins C and E have lower pulmonary functioning than those with at least a moderate intake.

Investigators have identified yet another reason for kids to watch what they eat: High school seniors whose diets were low in fruit, vitamins C and E, and n-3 fatty acids were found to have decreased lung function and were at a greater risk for a number of chronic respiratory diseases. According to lead author Jane S. Burns, ScD, and a team of researchers from the Harvard School of Public Health in Boston, the US Environmental Protection Agency, and Health Canada, smoking further increased the risks. The researchers published their findings in the July Chest.

“Teens who had both a diet low in antioxidant vitamins C and E and smoked were most likely to report symptoms of chronic cough, phlegm, and bronchitis,” Dr. Burns, a research fellow in the Department of Environmental Health at the Harvard School of Public Health, told Pulmonary Reviews.It appears that persons with poor diets may be more susceptible than others to the deleterious effects of smoking, she asserted.

Food frequency questionnaires completed by more than 4,000 twelfth-grade students in the US and Canada focused on dietary intake of antioxidants in the form of fruits and vegetables (and specifically of the micronutrients beta-carotene and vitamins C and E), as well as of nutrients such as retinol and n-3 fatty acids, which have an effect on cell function and inflammatory processes. “Vitamin supplements were included in the total dietary intake,” the authors noted. A total of 2,112 students also submitted to full pulmonary function testing for the dietary analysis. The majority of participants were white (89%), about one-third were overweight (BMI > 25), and 11% took daily multivitamins. Nearly one quarter reported daily smoking, with no significant difference between genders.

POOR EATING HABITS ARE COMMON

“Most of the adolescents in this cohort had dietary intakes of fruit, vegetables, vitamins, and n-3 fatty acids below the recommended levels,” stated the authors. Eighty-six percent of respondents reported consuming less than the recommended five servings per day of fruits and vegetables, and 39% did not meet recommended levels of vitamin A. At the worst, 99.9% of the participants reported less than the recommended intake of n-3 fatty acids; even those in the 80th percentile of n-3 fatty acid consumption had a mean daily intake of only 85 mg/d, compared with the recommended 300 to 500 mg/d.

Vitamin C, intake of which came primarily from consumption of vitamin-C fortified drinks, was the only nutrient that had a greater than 80% adherence rate, with only 18% of respondents not reaching the recommended 65 to 90 mg/d (exact recommendations depend on age and gender). Even participants in the lowest quintile reported an average 75 mg/d; however, those with less than 85 mg/d remained at greater risk for lower pulmonary function, including lower FVC and FEV1, than did those with a larger intake. “This suggests the current dietary reference intake for vitamin C may not be adequate to protect lung function,” asserted Dr. Burns and colleagues. Minimal fruit intake was also associated with reduced FEV1.

Participants with poor dietary habits also had increased odds of reporting chronic bronchitis, asthma, and wheeze, according to the study results. Those who reported intake of less than one-quarter of a serving of fruit per day had an odds ratio (OR) of 1.34 for asthma, and an OR of 1.36 for chronic bronchitis symptoms when compared with participants who ate more fruit. And compared with moderate intake, low intake of vitamin E (< 5.2 mg/d) resulted in increased odds of reported asthma (OR, 1.48), and low n-3 fatty acid intake (< 22 mg/d) resulted in increased odds of reported asthma, chronic bronchitis symptoms, and wheeze (ORs, 1.68, 1.37, and 1.34, respectively).

ROOM FOR IMPROVEMENT

The authors noted that their cross-sectional study “cannot establish the temporal relationship between diet and respiratory outcomes.” Dr. Burns suggested that a critical period for a diet’s effect on the respiratory system may exist during early childhood, and the clinical consequences might not be immediate. “However, if potential maximum pulmonary function is not obtained due to diet lacking in sufficient amounts of these nutrients, and is further impacted by airway remodeling due to chronic bronchitis and wheeze, this may predispose these teens to increased morbidity and earlier mortality later in life,” she said. The researchers suggested vitamin supplements to assist adolescents in reaching their daily intake goals, although promotion of fruit and fish consumption is also needed to ensure adequate intake of antioxidants and n-3 fatty acids, as those are not always included in the supplements. They also highlighted prevention of the onset of smoking as a primary objective of health promotions targeted at adolescents.             

—Jessica Dziedzic

Reference
Burns JS, Dockery DW, Neas LM, et al. Low dietary nutrient intakes and respiratory health in adolescents. Chest. 2007;132(1):238-245.

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