Study participants who reported eating more fruit and soy fiber as adults seemed to be protected against some of the negative health effects often associated with early tobacco exposure.

Individuals 18 or younger, living with one or more smokers, were more than twice as likely to suffer from chronic dry cough as adults, according to a new study published by researchers at the National Institute of Environmental Health Sciences (NIEHS), the University of Minnesota, and the National University of Singapore. This paper, which appears online in Thorax, is the largest study to date on the effects of childhood exposure to environmental tobacco smoke (ETS) on later respiratory disease, and the first to include data on dietary intake.

"This research adds to a growing body of evidence that exposure to second-hand smoke early in life has health consequences that can last a lifetime," said Dr. David Schwartz, Director of the NIEHS. "In addition to finding ways to reduce the exposure of children to tobacco smoke and other environmental pollutants, we also need to look for ways to reduce the disease burden."

The data for this study were collected from the Singapore Chinese Health Study, a population of men and women of Chinese ethnicity ranging in ages from 45 to 74 at enrollment, who live in Singapore. The 35,000 non-smokers provided information regarding ETS before and after age 18, a medical history including information on respiratory symptoms of chronic cough, phlegm production and asthma diagnosis, as well as information on dietary intake.

Chronic cough was defined as occurring on most days for at least three months of the year and lasting more than two years in a row. More than 45 percent of the study participants reported having fathers who smoked, and 19 percent reported having mothers who smoked. The researchers found that more smokers in the home during childhood, was linked to a greater incidence of chronic cough, and chronic phlegm.

"Because we had previously found in this Singaporean population data suggesting that a diet high in fruit and soy fiber may reduce the incidence of chronic respiratory symptoms, we decided to study the impact of fiber on problems associated with early tobacco exposure," said NIEHS researcher Stephanie London, M.D. "We actually found that people who ate even a small amount of fruit fiber had less chronic cough related to environmental tobacco smoke."

Study participants who ate more than 7.5 grams of fiber each day had fewer health effects associated with ETS. This is equivalent to eating about two apples a day. Dr. London pointed out that the average weight of the Singapore study participants was 127 lbs. She also added that most Singaporeans get their fiber from fruits, vegetables and soy.

"Fiber may have beneficial effects on the lung," said Dr. London. "It seems to have the ability to reduce blood glucose concentrations, reduce inflammation, and enhance antioxidant processes. All of these may help to protect the lung against environmental insults, such as ETS in childhood. However, the possible benefits of fiber should not lessen the importance of reducing exposure to environmental tobacco smoke."

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