Un nou concept în prevenirea alergiilor: antrenarea sistemului imunitar

Introduction

It is by now recognized that the earliest nutritional influence on atopic disease in infants is the nutritional diet of the pregnant woman. However, not all studies have supported the protective effect of a maternal exclusion diet (including the exclusion of cow milk and eggs) on the development of atopic disease in infants, as summarized in a 2006 Cochrane review(3,4,5). 
Although data is still conflicting, there is no demonstrated significant benefit for children whose mothers had a restrictive diet during breastfeeding(6,7,8). There was found a possible reduction of the incidence of atopic dermatitis in children in their first two years of life in some studies, but no difference after two years(9).
Short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides (GOS/FOS) supplementation of the partially hydrolysed cow’s milk formula influences the immune system by lowering IgE, that is directly involved in the allergic mechanism, and also by lowering the IgG1, IgG2 and IgG3, whereas no effect on IgG4 was observed. The IgG1 value of the cow’s milk protein decreases significantly when prebiotics are added to the fomula(10).
The use of prebiotics is one of the tree strategies used in manipulating the intestinal microbiota. Prebiotics are undigestible food ingredients that stimulate selectively the proliferation or/and the activity of the already existing bacterial population. This strategy offers more advantages than the use of antibiotics or probiotics (Table 1). 
 

Recent studies have brought more and more evidence that suggests that early colonization of the intestinal tract by an appropriate intestinal microbiota is very important for the healthy maturation of the immune system(11). Although it is well known that the only food that satisfies the nutritional needs of a newborn is human milk, there are cases when breastfeeding is interrupted and babies are fed with infant formula, or cases of mothers who don’t produce enough milk in order to fulfill the nutritional needs of the baby and they add infant formula. There are several studies which reported that the oligosaccharides found in human milk acted as prebiotics(12,13). 
Particularly, studies have shown that by adding prebiotics (galactooligosaccharides and fructooligosaccharides) mixtures to the infant formula, the growth of bacilli and Bifidobacteria is being stimulated(14), which lead to a change in the chain of fatty acids, making their biological profile closer to the one observed in infants who were breastfed, and also reduces the incidence of infections and allergic events during the first two years of life(15). 
The positive effects of using probiotics have stimulated an intense interest in determining if the same results can be achieved by using prebiotics. Some animal feeding studies have demonstrated that prebiotics can induce the immune response of Th1, re-balance Th2 biased responses, and also suppress allergenic synthesis of IgE. Currently, there have been reports from different randomized controlled studies which concluded that prebiotics may be able to replicate the exact benefits that have been seen for probiotics in the prevention of allergies(16).
Prebiotics added to infant formula rarely produce any side effects. Among the minor effects that can appear, we can mention flatulence or abdominal bloating, but only for doses greater than 20 g per day, and diarrhea and abdominal cramps for doses greater than 50 g per day(17).
Although World Allergy Organization (WAO) recommends the use of prebiotic supplements in not exclusively breastfed infants and not using the prebiotic supplement in exclusively breastfed infants, a recent study, made by Boyle et al.(18), concluded that the use of pHF-prebiotic formula showed a persistent immune-modulatory effect and, possibly, also reduced the occurrence of allergic manifestations in infants to whom solids were introduced in the diet according to guidelines (>18 weeks).

Conclusions

Despite some studies that showed an increased risk of allergic disease with exclusive breast-feeding, the overall benefits of breastfeeding on the general health of the child are likely to outweigh the potential drawbacks, regardless of the allergic status of the mother or child.
The prevention of allergy symptoms is very important in order to reduce the risk of chronic disease in the adult life. Although the current guidelines do not recommend the use of prebiotics, more targeted studies have shown beneficial effects, mostly in reducing the occurrence of allergic manifestations in infants to whom solids were introduced in the diet according to guidelines.