Worryingly, these allergic reactions have increased to such an extent that up to 40% of young children are now believed to suffer from atopic disease, according to a recent article by Prof G.F. Kirsten of the Tygerberg Department of Paediatrics and Child Health published in Current Allergy & Clinical Immunology.
Prof Kirsten suggests that the exposure to proteins that occur in foods may possibly be implicated in this increase. Consequently, one would expect that babies who are exclusively breastfed will be exposed to fewer food proteins and develop fewer allergic reactions. In fact, nearly 70 years ago researchers found that breastfed infants had a much lower incidence of eczema than bottle-fed infants.
But subsequent research hasn't always supported this finding and some studies even indicate that breastfeeding by allergic mothers may transfer allergies to their infants. There is, therefore, some controversy about what the mothers of allergic babies should, and shouldn't, do.
A link between mother and baby
The human body is a marvellous system, as is demonstrated during pregnancy when microorganisms and antigens from the mother’s intestines are taken up in immunological cells in the mother’s body to stimulate the production of powerful immunological factors called T and B lymphocytes.
These white blood cells, or lymphocytes, then migrate to the mammary glands towards the end of pregnancy, which is called “homing”. In the mammary glands, the lymphocytes produce so-called secretory IgA antibodies, which combat the microbes and antigens that occur in the mother’s intestines. This amazing system is called “the enteromammary link” (Kirsten, 2009).
When a baby is born by normal birth, it comes into contact with the mother’s perineum, which colonises the baby’s gut with the mother’s intestinal bacteria. As soon as the baby receives colostrum and breast milk, it's provided with a bountiful supply of secretory IgA antibodies and other infection-fighting factors. This protects the infant against invasion of microorganisms and allergens through the intestines.
Finally, the so-called "Bifidus factor" in breastmilk colonises the infant’s gut with Lactobacilli and Bifidobacteria (both essential and protective microorganisms) and starts to stimulate the production of T-helper 1 cell responses in the infant, which also protect against allergies (Kirsten, 2009).
The use of friendly microorganisms in the form of probiotics during pregnancy and lactation may well benefit the above-mentioned process of immunity transfer from mother to child and reduce the incidence of atopic disease in infants.
Studies have found that giving pregnant women probiotics for the last four weeks before birth and during milk production reduced the number of infants with atopic dermatitis and increased the levels of protective factors in mother’s milk (Kirsten, 2009).
Although some researchers have found that cows’ milk protein, wheat, egg or peanut allergens appear in breastmilk for up to four days after a mother has eaten these foods, there is no concrete evidence that the presence of these allergens in breastmilk cause allergies in babies receiving such milk.
The use of restrictive diets that exclude the offending foods listed above by mothers breastfeeding their infants, has not proved an efficient method of preventing atopic disease. For example, one study showed that there was no link between the intake of peanuts in mothers’ diets and the development of peanut allergy in their children.
Putting mothers on restrictive diets may even have negative effects on the nutrition of the mother and her infant. The Committee on Nutrition, Allergy and Immunology of the American Association of Pediatrics stated that there's not enough evidence to warrant dietary restrictions during pregnancy in an attempt to reduce allergies in babies (Kirsten, 2009).
How long should a baby be breastfed?
Modern researchers have also found that breastfeeding reduces the risk of asthma and other atopic diseases in infants and that the duration of breastfeeding plays an important role.
The consensus among the leading allergy and nutrition advisory bodies is that babies should be exclusively breastfed for a minimum of four months. If they can be breastfed for six months, this is even better. These organisations also recommend that solid foods shouldn't be introduced before the baby has reached the age of four to six months.
Children exposed to a high risk of allergies (for example, those with a genetic tendency) shouldn't be given fish, eggs and peanut protein until they're considerably older (Kirsten, 2009).
The bottom line
The conclusions we can reach at the present moment are as follows:
- The use of probiotics that contain Lactobacilli and/or Bifidobacteria during the last month of pregnancy and during breastfeeding may be beneficial.
- Mothers don't need to use restrictive diets when breastfeeding potentially atopic infants and such restricted diets can lead to poor nutrition in both the mother and the infant.
- Exclusive breastfeeding up to the age of six months is desirable.
- Introduction of solid foods should be delayed to the age of four to six months, with an even longer delay for foods such as fish, eggs and peanuts in severely atopic children.
(Dr I.V. van Heerden, DietDoc, April 2009)
(Kirsten GF (2009). Does breastfeeding prevent atopic disorders? Current Allergy & Clinical Immunology, Vol 22, No1:24-25.)