TURKU, FINLAND. An atopic disease is a form of allergy where the hypersensitivity reaction occurs at a location different from the initial contact point between the body and the offending agent (allergen). For example, food taken by mouth may cause an allergic skin reaction - atopic dermatitis. The incidence of atopic diseases such as dermatitis, allergic rhinitis, and asthma is rising in industrialized countries and now affects about 20% of the population.
A team of researchers from the University of Turku and Tufts University in Boston now report that the increase in atopic diseases is closely tied in with an increase in the consumption of omega-6 fatty acids (linoleic acid) which have pushed the ratio of omega-6 to omega-3 (alpha-linolenic [ALA], eicosapentaenoic [EPA], and docosahexaenoic [DHA] acids) fatty acids in the diet to an unfavorably high level (10:1 or higher). An increasing dietary intake of linoleic acid has been linked to a rise in atopic diseases in both Germany and Japan. A recent study of Finnish and Swedish school children found that children with a high ratio of eicosapentaenoic acid (EPA) to linoleic acid had a lower prevalence of atopic diseases while children with allergies tended to have a lower level of docosahexaenoic acid (DHA) in their blood.
The researchers point out that the metabolic products (eicosanoids) of omega-6 fatty acids promote inflammation while the metabolites of omega-3 acids (such as DHA and EPA, which are both found in fish oil) dampens inflammation. They also point to several clinical trials which have shown that supplementation with alpha-linolenic acid or fish oil can reduce the symptoms of atopic dermatitis and asthma. They conclude that an increased intake of omega-3 fatty acids (alpha-linolenic acid and fish oil) may alleviate atopic diseases caused by an excessive intake of omega-6 fatty acids.
Kankaanpaa, Pasi, et al. Dietary fatty acids and allergy. Annals of Medicine, Vol. 31, 1999, pp. 282-87 [61 references]