Allergic diseases often occur in early childhood. These diseases are the result of a changed response by the infant's immune system to substances such as cows' milk protein, egg protein, pollen or house-dust causing symptoms like wheezing, sneezing or itchy rashes. Signs of this change in the immune response can be seen in laboratory tests on cells from the blood taken at birth. These signs are not clear enough to predict later allergic disease in the child but they allow us to realise that the allergic disease process starts very early, even before the baby is born.

Omega 3 consumption

The increase in numbers of children affected by allergies coincides with a decrease in consumption of oily fish containing omega 3 fatty acids in the general population. 

There are two main dietary theories addressing why we are experiencing this increase in allergies: 

1. Less Ω-3 PUFAs in the diet 

2. Less protective antioxidants in the diet 

These theories may be of particular importance during pregnancy. There is evidence that babies who will later develop allergic symptoms are born with an altered immune system when compared with babies who do not develop allergies. Allergic symptoms are caused by an inappropriate immune response to foods and substances which the immune cells normally ignore. The discovery that differences exist in the immune system at birth suggests that such dietary effects on the baby may occur through the mother in pregnancy. Sensitisation to allergens occurs very early in life, perhaps even in utero. Studies have shown that mothers who eat more fish have babies with fewer allergies than mothers with a low intake of fish. Children who are affected by allergies have lower amounts of Ω-3 fatty acids in their blood and blood cells. This suggests that increasing the supply of Ω-3 fatty acids to babies, even before they are born, may help to “normalise” their levels of Ω-3 fatty acids and lessen their chances of developing allergies. 

Epidemiological studies suggest that fish consumption provides a protective effect towards childhood atopy and allergy during pregnancy or in infancy/early childhood.However, such data only suggest associations and do not show cause and effect.Proof of a causal effect is required from intervention studies.

The aim of the Salmon in Pregnancy Study This was the first intervention study in which oily fish was given to pregnant mothers. The aim for this study was to improve the mothers’ nutrient levels focusing particularly on Ω-3 PUFAs, selenium – an antioxidant known to be important for immune cell function - and vitamin D. Also, it was put forward that the oily fish intervention may improve the babies’ nutrient levels. Finally, it was hoped that the improved availability of Ω-3 PUFAs, selenium and vitamin D might reduce either the number of babies developing allergies or the severity of atopic symptoms.