Salmon in Pregnancy Study
Condition: Dermatitis; Allergies; Asthma
MeSH terms: Dermatitis
Study type: Interventional

Summary: 
      The number of infants and children with allergic disease (dermatitis, allergies, asthma) has
      increased over the last several decades. This may be related to changes in diet. It is now
      thought that children become sensitised to allergens very early in life maybe even before
      they are born. Some studies show that a high omega-3 fat intake by mothers decreases risk of
      sensitisation in their babies. There is a biological mechanism to explain this. Omega-3 fats
      are found in oily fish like salmon. In the UK pregnant women are recommended to eat oily fish
      twice per week. However, consumption of oily fish is known to be low in pregnant women in the
      UK. This study sets out to identify the effects of increasing salmon intake in pregnant
      women. The hypothesis being investigated is that : increased consumption of oily fish during
      pregnancy by women at risk of having offspring who will develop atopy will increase their
      omega-3 fat and antioxidant status and that of their developing baby and will ameliorate the
      development of atopic markers and manifestations in the infants.
    

Detailed description: 
      The prevalence of childhood atopic diseases (eczema, rhinitis [hay-fever], asthma, allergies)
      has increased dramatically over the last 30 years or so. This must be due to environmental
      changes. Dietary change is believed to be an important causative factor and three diet
      related hypotheses have been proposed. The first of these ("the PUFA hypothesis") is that the
      increase in intake of n-6 polyunsaturated fatty acids (PUFA) over the last 30 years has
      resulted in an absolute and relative decline in intake of n-3 PUFA, especially long chain n-3
      PUFA. There is a plausible biological mechanism whereby a high n-6 to n-3 PUFA ratio would
      skew the immune system to favour sensitisation to allergens. The second diet hypothesis ("the
      antioxidant hypothesis") is that there is a lower status of antioxidant vitamins and minerals
      than 30 years ago and that the resulting increased oxidant stress skews the immune system to
      favour sensitisation to allergens. The third diet hypothesis ("the gut microflora
      hypothesis") is that the maturing microflora within the intestinal tract of the neonate plays
      a role in development of atopy through interactions with the gut immune system. Factors that
      influence development of neonatal gut microflora include maternal gut microflora and infant
      diet (e.g. breast milk composition). Since maternal diet will affect maternal gut microflora
      and also breast milk composition a link is suggested between modification of the maternal
      diet in pregnancy and development of atopy in the infant through an effect on gut microflora.

      It is now recognised that sensitisation to the allergens that trigger atopic disease occurs
      early in life, and in many cases in utero [4]. Thus, it is most likely maternal diet during
      pregnancy that is important in influencing risk of atopic disease in children. There is much
      evidence that n-3 PUFA status is lower in plasma, erythrocytes, white cells and milk of
      mothers of atopic children and also in umbilical cord plasma and erythrocytes [5]. Likewise,
      the status of some antioxidant minerals (e.g. Se) in cord blood has been reported to be lower
      in children who went on to develop atopic disease than in those who did not. Finally, atopic
      infants have a different gut microflora than non-atopic infants. These studies suggest that
      maternal status of n-3 PUFA and antioxidants, and possible of certain gut microbes, is
      important in determining atopic outcome in children. Not surprisingly therefore, there is
      substantial interest in supplementation studies in pregnant women, particularly those whose
      babies are at risk of atopic disease (e.g. from a family history). Fish, especially oily fish
      like salmon, and fish oil are very good sources of long chain n-3 PUFA. A recent study
      investigating the effect of fish oil supplementation in pregnant women reported an alteration
      in the cytokine profile of umbilical cord plasma that is consistent with protection towards
      atopy. The study went on to demonstrate a reduced severity of atopic dermatitis and a
      decreased likelihood of skin-prick positivity to a variety of common allergens in the
      children at one year of age. Oily fish represent a unique opportunity to reduce atopy risk
      because they are rich sources of both n-3 PUFA and antioxidant minerals (Se). They represent
      a more attractive option than supplementation with fish oil capsules. Pregnant women have a
      low intake of fish. Current UK recommendations are that "women of reproductive age should aim
      to consume within the range of one to two portions of oily fish a week". The upper limit of
      this range is below that for the recommendations made for boys, men and women not of
      reproductive age. This is because of concern about contaminants in some species of oily fish
      (e.g. tuna). Aquaculture producing salmon with low contaminant levels is therefore an ideal
      solution to enable oily fish consumption by pregnant women. Consumption of tailor-made salmon
      by pregnant women could prevent the development of atopic disease in their children. It is
      important that this be assessed through a well-designed and rigorous intervention study
      relating maternal oily fish consumption to atopic disease in the offspring, at the same time
      assessing effects of maternal fish consumption on fetal growth and maternal and fetal body
      composition.

      Hypothesis:

      Increased consumption of oily fish during pregnancy by women at risk of having offspring who
      will develop atopy will increase their n-3 PUFA and antioxidant status and that of their
      developing baby and will ameliorate the development of atopic markers and manifestations in
      the infants.

      Objectives:

        1. To conduct a dietary intervention study in pregnant women using long chain n-3 PUFA-rich
           salmon.

        2. To determine the effects of increased consumption of oily fish during pregnancy on fetal
           growth and adaptations and on maternal and fetal body composition.

        3. To determine the effects of increased consumption of oily fish during pregnancy on
           maternal and fetal (i.e. cord blood) nutrient status

        4. To determine the effects of increased consumption of oily fish during pregnancy on
           maternal and fetal (i.e. cord blood) immune status

        5. To determine the effects of increased consumption of oily fish during pregnancy on
           predictors of atopic disease in cord blood, and on the development of atopic disease in
           infancy.
    

Intervention name(s): Oily fish consumption; Control
Intervention type(s): Dietary Supplement; Other
Intervention description(s): Two portions of salmon per week from week 20 of pregnancy until giving birth; No change to habitual diet from week 20 of pregnancy until giving birth
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Investigator)
Primary purpose: Basic Science
Keywords: Omega-3; Oily fish; Antioxidant; Selenium; Atopic disease; Pregnancy; Nutrient status