Antioxidants and allergic disease: a case of too little or too much?

Abstract

Speculation persists as to the possible role, if any, of dietary antioxidants in allergic disease. While it has been hypothesized that the recent increase in allergic disease is a consequence of declining dietary antioxidant intake, an alternative hypothesis proposes that the increase in allergic disease is due to increasing antioxidant intake. Dietary trends are conflicting; the intake of some antioxidants has declined, for others intakes are likely to have increased. Animal model studies demonstrate that antioxidant supplementation at the time of primary and subsequent allergen exposure attenuates allergic inflammatory responses. The data from human studies are less clear. Observational epidemiological studies of humans are beset by several methodological limitations associated with the assessment of diet and predominantly focus on asthma. Most observational studies report potentially beneficial associations between dietary antioxidants and allergic outcomes, but a small minority report potentially adverse associations. Human intervention studies suggest that single antioxidant supplements confer minimal, if any clinical benefit in adults with asthma, however, there is still scope for studies in children, atopic dermatitis, allergic rhinitis (AR) and of antioxidant combinations. More recently, it has been suggested that dietary antioxidants in the developmental context of fetal and infant development influence the development childhood asthma and atopic sensitization possibly by affecting the first interactions between the neonatal immune system and allergens. While a small number of birth cohort studies have reported potentially beneficial associations between maternal intake of some antioxidants during pregnancy and childhood asthma, there is very limited data suggesting associations between maternal antioxidant intake and childhood atopic dermatitis and AR. The available epidemiological, animal, molecular and immunological data suggest that there are associations between antioxidants and asthma and to a much lesser extent, atopic dermatitis and AR. However, the exact nature of the relationships and the potential for therapeutic intervention remain unclear.

Does maternal diet during pregnancy and lactation affect outcomes in offspring? A systematic review of food-based approaches

“…The first is that dietary antioxidants are protective against oxidant damage and inflammation of airways. Decreased dietary antioxidants have been suggested as one cause of the increased prevalence of atopy in the Western world [69,85]. The opposing theory suggests that increased or excessive antioxidant intake suppresses T helper cell type 1 differentiation and because of immune regulatory mechanisms, promotes the development of a T helper cell type 2 profile (towards atopy) [85].…”

Fatty Acids as Biocompounds: Their Role in Human Metabolism, Health and Disease - A Review. Part 2: Fatty Acid Physiological Roles and Applications in Human Health and Disease

“…Moreover, exposure to specific nutrients and factors via breast milk is critical for development 62 . With regards to this, many factors have been characterised to be crucial in development such as exposure to pollutants, intake of folic acid, vitamin D, antioxidants such as selenium [63][64][65] , and most importantly FA (ref. 66,67 ).…”

The Potential of Maternal Dietary Modification for Prevention of Food Allergy

“…The available epidemiological, animal, molecular and immunological data suggest potentially beneficial associations between maternal intake of some antioxidants during pregnancy and childhood asthma and to a much lesser extent, atopic dermatitis and allergic rhinitis (reviewed in [59]). To date, no such data are available for food allergy.…”