Healthnotes Newswire (January 11, 2001)—Supplementation with fish oil capsules improves the symptoms of asthma in children, according to a new trial published in the European Respiratory Journal.¹ While several previous trials of fish oil for asthma have come up empty-handed, the current trial renews hope that fish oil supplements may benefit children with this common and often debilitating condition.

The double-blind trial compared the effects of fish oil supplementation (300 mg per day for 10 months) vs. placebo among children with bronchial asthma, a lung disorder in which spasms and inflammation of the bronchi (tubes that carry air in and out of the lungs) restrict normal breathing. After six months of supplementation, researchers observed significantly fewer asthma symptoms among the children who were taking the fish oil, an effect that continued to improve until the end of the trial. The placebo group, in contrast, experienced only transient improvements, which were not evident by the end of the trial.

An unusual feature that distinguishes this study from previous trials of fish oil for asthma is that participants were in residence at the clinic approximately 85% of the time, including the time they attended school. Because the environment was so strictly controlled, exposure to food allergens and environmental allergens, common triggers of asthma attacks, was minimized in both the fish oil and placebo groups.

An asthma attack usually begins with sudden fits of wheezing, coughing, or shortness of breath. However, it may also begin insidiously, with slowly increasing manifestations of respiratory distress. A sensation of tightness in the chest is also common.

Who is Affected?

The number of asthma sufferers has more than doubled from 6.7 million in 1980 to 17.3 million in 1998. An estimated 4.8 million are children. Asthma is the leading serious chronic illness among children. Only about a quarter of the children with asthma become symptom-free as adults; the condition persists beyond childhood in 85 percent of women and 72 percent of men.² Asthma accounts for nearly 500,000 hospitalizations each year, and asthma deaths have tripled over the past two decades. Despite improvements in clinical treatment, visits to emergency rooms and hospitalizations due to asthma are increasing. It is estimated that in the year 2000, asthma-related costs exceeded $14.5 billion.³ There is no known cure for asthma.

An Inflammatory Disease

Asthma is an inflammatory disease. Fish and fish oil are rich in omega-3 fatty acids (EPA and DHA), which help fight inflammation.^{4 5} There is evidence that children who eat oily fish may have a much lower risk of getting asthma.⁶ However, dietary supplementation with fish oil has not always demonstrated a significant effect on asthma symptoms in clinical trials. One double-blind trial showed that fish oil partially reduced reactions to allergens that can trigger attacks in some asthmatics.⁷ Other researchers have reported small but significant improvements when asthmatics supplement fish oil.^{8 9} But reviews of clinical trials on fish oil for asthma found that most studies came up empty-handed.^{10 11}

It is possible that the failure of previous trials was due to inadequate study length in which to demonstrate an effect. For example, previous trials of fish oil supplementation for asthma lasted only 10 weeks,⁷ 6–14 weeks,¹² and 6 months,^{13 14} compared with the current study’s 10 months. However, in all likelihood, the success can be attributed to participants being in residence for the study, which strictly controlled exposure to common asthma triggers. Further studies are needed to confirm these results. Parents wishing to use fish oil for their children with asthma should consult a healthcare practitioner. Other natural therapies have also been reported to reduce asthma symptoms, including vitamin B6,¹⁵ vitamin C,¹⁶ magnesium,¹⁷ and ivy leaf (Hedera helix) extract.¹⁸ But for each of these therapies, fish oil included, evidence exists that challenges the positive outcomes.

Why is Asthma Becoming More Widespread?

The cause of asthma remains mysterious to researchers. Thus, it is difficult to explain the skyrocketing incidence of asthma over the past 20 years. However, several theories have been proposed.

A so-called Western lifestyle has been the factor most commonly cited to explain the troublesome increase in asthma prevalence. This lifestyle implies a way of life where children are exposed from early infancy to a wide range of foods, indoor and outdoor allergens and irritants, and to the effects of motor vehicle pollution.¹⁹

Increased air pollution, including ozone, particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead, have been blamed for the increased prevalence of asthma.²⁰ All of these agents interfere with normal oxygen delivery in the body, and may therefore be of special concern to persons with asthma.

Changes in house construction and living conditions combined with increased time spent indoors have increased exposure to relevant allergens.²¹ For example, increased exposure to dust mites has been proposed as a possible explanation of the rising incidence of asthma,^{22 23} though some researchers do not agree that reducing environmental exposure to dust mites controls asthma episodes.²⁴ Added to these concerns is a reported increased use of allergenic building materials in homes, schools, and public buildings. This may partially account for the high incidence of asthma triggers reported in schools²⁵ and in other locations.

The burden of low socioeconomic status may play a role in the increased incidence of asthma. Racial and ethnic minorities of low socioeconomic status residing in urban environments appear to be disproportionately at high risk for asthma-related symptoms and death. Population studies suggest that key risk factors contributing to asthma within the inner city include social demography, the physical environment (indoor and outdoor), and healthcare access and quality.²⁶

A decline in physical activity of children, particularly those living in poverty in the United States, could have contributed to the rise in asthma.²⁷ This theory is supported by the findings of a study published in the same issue of the European Respiratory Journal as the current fish oil trial for asthma. In that study, low physical fitness in childhood was associated with the development of asthma, whereas high physical fitness appeared protective against the disease.²⁸