The role breastfeeding plays in preventing allergies and asthma in children is unclear.
Studies undertaken since the 1980s have provided conflicting information about whether breastfeeding is more likely or less likely to protect infants from developing these conditions.
For instance, a Swedish study found that exclusive breastfeeding during the first four months of life reduces an infant’s likelihood of having asthma. Meanwhile, a New Zealand study found that breastfeeding may double the eventual risk of asthma and allergies for a child. It is possible that breastfeeding may protect a child against allergies and asthma during the early years, but may increase the likelihood of developing these conditions later.
What is beyond dispute is that breastfeeding offers many benefits for children (and mothers) apart from allergy/asthma protection. For this reason, most experts continue to strongly urge new mothers to breastfeed their babies exclusively for at least the first six months of life. Some recommend at least partial breastfeeding for up to one year.
Impact on allergies and asthma
Breastfeeding is highly recommended for many reasons. Breast milk contains nutrients vital to the development and health of a baby, promotes bonding with the mother and has health and emotional benefits for the mother as well. In recent years, many healthcare experts have also praised the virtues of breastfeeding as a means of protecting children from developing allergies (exaggerated reactions of the immune system to certain foreign invaders that it mistakes as a threat to the body) and asthma (chronic inflammation of the airway tissues). However, more research is necessary on the topic.
To date, studies on the effects of breastfeeding on the development of allergies and asthma are inconclusive. While some researchers have found lower incidence of allergies and asthma in breastfed children, other studies indicate this protection may be temporary. Breast milk may pass on the tendency for allergies/asthma later in life.
Among the most frequently cited claims is the notion that exclusive breastfeeding for the first year of life protects infants from developing food allergies (a potentially fatal response by a person’s immune system to a food or food component). A diet made up exclusively of mother’s milk at least temporarily protects infants from exposure to potential food allergens (any food component or additive that, when ingested, is mistakenly perceived as a threat, triggering an exaggerated reaction by the immune system), especially soy and cow’s milk.
According to this theory, keeping allergenic foods from newborn babies is crucial because the baby’s intestines have not yet matured and are more open to potentially allergy-causing proteins. Thus, giving only human milk during the first six months of an infant’s life keeps potentially allergy-causing proteins out of the bloodstream during this crucial time and at the very least delays the onset of allergies. However, this is still only a theory.
Few healthcare experts question the health benefits of breastfeeding, and mothers are urged to exclusively breastfeed for at least the first four to six months of life, with many physicians recommending it for the first six to 10 months. Some experts suggest partial breastfeeding (breastfeeding supplemented with infant formula) up to a year. Whether or not this will protect the child from food allergies remains open to debate.
Some studies have found that breastfeeding mothers who eat foods associated with allergies (including peanuts, milk, eggs and many others) may pass on exposure to these allergens through their milk. These studies have found that some infants thus become sensitized (made sensitive) to the allergen, setting them up for allergic reactions upon future exposures. Conversely, other studies have found evidence that the transmission of food allergens can be beneficial, allowing infants to build up a tolerance to the allergen that is likely to prevent future allergic reactions.
Although there is no conclusive evidence that either of these theories is correct, many physicians discourage nursing mothers with a strong history of allergies from eating certain foods associated with allergies (e.g., tree nuts, sesame, peanuts). Mothers with a personal or family history of food allergies should discuss breastfeeding with an allergist and their child’s pediatrician.
Mothers should also consult a physician when they suspect that their child is reacting to food allergens being passed through their breast milk. The physician may recommend the removal of certain food allergens from the mother’s diet. Signs of food allergies in infants may include diarrhea, vomiting, skin rashes, eczema (a skin condition exacerbated by food allergies) and runny nose. Changes in the mother’s diet often reduce or eliminate the symptoms.
It is important to note that women should not modify their diets without first consulting a physician. Changing one’s diet without the supervision of a physician can lead to an unbalanced diet and a number of resulting health problems.
In some cases, as with peanuts, a food may not be essential because the nutrients are readily obtained elsewhere. However, milk is an important source for calcium and will have to be replaced with alternate foods high in calcium or calcium supplements.
Breast milk itself is very complex, and determining how it can prevent or possibly contribute to allergies is difficult. In addition, many of the studies to date on the impact of breastfeeding on allergies did not include a controlled diet for the mothers. Therefore, it cannot be known whether variables in the mothers’ diets impacted the study results. Even in studies where the mothers’ diets were controlled, evidence of long-term allergy protection is lacking. The methods of conducting research can also vary from study to study, making comparisons difficult.
As with allergies, various studies have reached different conclusions on the impact of breastfeeding and asthma risk. Some cite strong evidence that breastfeeding lowers the risk of asthma and some suggest it has no impact or may offer only temporary protection (followed by an increased likelihood of developing asthma later in life).
The complexity of definitively answering this question is evident in a University of Arizona study, which found that atopic children (children with a genetic tendency to develop allergic diseases) who are breastfed by mothers with asthma are more likely to develop asthma after age 2, but less likely to develop asthma before that time.
However, it is an established fact that breastfeeding reduces an infant’s likelihood of contracting respiratory infections, which are believed to contribute to the development of asthma.
In the face of such confusing research, many experts advise breastfeeding mothers to eat a well-balanced diet to ensure that their babies get the nutrients they need for proper development. A mother should consult a physician before changing her diet to ensure she and her child get adequate nutrition.