Enhancing Infant Immunity by Alessandro Ferretti Dip ION

Becoming a father for the first time brings with it many challenges. Perhaps the greatest of all being the knowledge that the choices you make as a parent will have a profound impact on your infant’s health, well-being and development. As the proud father of Milo, just turned 1 year old, I am of course hugely interested in the whole field of infant nutrition, and none more so than the area of immunity and allergies. In this article I would like to share with you some of the fascinating connections and latest research relating to the development of infant immunity.

We often talk about ‘boosting’ immunity as if somehow our immune systems are consistently under-performing. Do we really want our immune cells to be on hyper-drive? What about if our immune cells are so ‘fired up’ that they start to attack our own cells, or food, or environmental substances? Isn’t this exactly what we are seeing more of in 21st Century life?

There is no denying the upward spiral of allergic and auto-immune conditions in Western industrialised countries. In Sweden, one third of all children under 11 have atopic disease. In the UK the number of children with asthma has doubled in the past decade. For allergies to be increasing at such a rate, it would suggest the underlying cause to be environmental rather than genetic.

Look across the globe and a surprising picture emerges, less developed countries have significantly lower allergy rates. Initially scientists explained away this global disparity by focusing on rising levels of pollution and house dust mites in Industrialised countries. Swedish scientist, Bjorksten, investigated this theory and found higher house dust mite levels in Estonian homes where the prevalence of allergies is low, compared to homes in Sweden where we have already seen that allergies are a growing problem. In the first year of life, Estonian children develop the type of immune response to mites that could lead to allergies, but very few develop allergic symptoms. Why the contradiction?

Bjorksten (1994) and Holt (1995) suggested a possible connection between the rise in Western allergies and a reduction in microbial pressure. A German study in 1979 reported a decrease in faecal Bifidobacteria in infants during the time period 1958 to 1978. A time when major changes in diet, lifestyle and healthcare were starting to take root in the Western world - industrially processed food, microwave ovens, freezers, antibiotics, the contraceptive pill, the rise of the supermarkets and loss of food seasonality.

Holt postulated that the bacteria within our intestines exerted a regulatory effect on the maturation of the immune system. Could it be true that the bacteria residing in our children’s intestines hold the key to the development and maturation of their immune system?

When a baby is born it is effectively sterile, i.e. not yet colonised by bacteria. Colonisation occurs as the infant makes contact with the outside world and microogranisms are rapidly acquired from the infant’s surroundings, namely Mum! The gastric content of a naturally delivered infant reflect the cervical flora within just 5-10 minutes of birth (Zetterstrom et al, 1994). Hygienic measure such as the use of antiseptic ointment or antibiotics, may postpone the transmission of bacteria from mother to infant (Murono et al, 1993). Whilst a number of other research studies have also highlighted a difference in the microflora of babies born in hospitals as opposed to a ‘less sterile’ home environment, it seems to be the infants food source that is the primary influencing factor in the development of microflora. Breast fed infants harbour more Bifidobacterium dominant colonies than their formula-fed counterparts.

Breast milk contains a number of different substances that influence immunity in a way that formula feed simply cannot match. On the first day of feeding, almost 4g of secretory IgA will be passed from mother to infant via breast milk. SIgA is an antibody, which binds to bacteria and potentially allergenic material to prevent infections of damage. Amazingly, this SIgA produced by the mother’s mammary glands and appearing in her milk, are a reflection of her own enteric and respiratory antigens. In other words, these are antibodies that relate specifically to the bacteria and antigenic substances to which the mother has recently been exposed!

This passage of immune factors is absolutely crucial in helping to protect the vulnerable newborn baby, but it does have its limitations. Immune protection is generally short-lived as the infant is not producing its own antibodies. In other words the immunity conferred is passive - Stop breast feeding and the protection stops.

Longer lasting active immunity develops as the infant’s immune system matures and ‘learns’ about the outside world. The latest thinking is that the microflora plays a crucial role in this immune maturation and development of oral tolerance. Think about what happens when we eat a meal, our immune system is presented with the considerable challenge of filtering out the nutritious bits whilst simultaneously deactivating infectious agents, allergens, carcinogens and toxins – no mean feat! But how do our cells know what is good and what is bad? This is what we mean by ‘oral tolerance’ and it a skill that our immune system has to ‘learn’.

The gut microflora seem to play a crucial role in the development of tolerance. A number of scientific studies have shown that sterile animals are defective in oral-tolerance – i.e their immune systems react strongly to foods and often fail to respond to infectious agents. Hamilton (1999) showed that mice delivered by caesarian section and raised in germ-free incubators were far more susceptible to infection. A dose of just 100 pathogenic bacteria caused the same degree of illness that would take a million times more bacteria in normal mice.

Hanson (1997) suggests that active stimulation and direction of the infant’s immune system takes pace through the development of the microflora. This in itself being directly influenced by the prebiotic oligosaccharides, lactoferrin and growth factors found in breast milk.

Weaning can also have an impact on an infant’s microflora. Researchers in New Zealand carried out an observational study on a group of 1210 children. Those exposed to 4 or more types of solid food at four months of age, had a 2.35 times greater risk of developing eczema than children still being exclusively milk fed at this age. Wilson et al (1998) concluded that to reduce the risk of developing allergies, breast-feeding should continue up to 15 weeks and no solid foods should be introduced prior to 15 weeks of age.

So in summary, there are many studies that show a strong link between ‘healthy’ gut flora and a ‘strong’ immune system. Much of the explanation behind this correlation remains speculative but it does appear that microorganisms provide a continuous low-level challenge to the immune system, allowing an infant to develop ‘normal’ responses to ‘normal’ things. I strongly believe that we are just starting to uncover this fascinating subject, and as we learn more about our symbiotic relationship with microorganisms, pre and probiotics will truly come into their own as a therapeutic treatment to optimise the maturation of the infant immune system and lessen the allergy epidemic. In the mean time, my advice is as follows:

  • Providing there are no complications, consider a home birth or ‘natural’ birth in a small rural hospital
  • Ensure close maternal contact especially in the very early stages of life, to ensure passage of beneficial bacteria.
  • Try to avoid antibiotics but if essential, replenish gut flora with a specialist infant probiotic such as BioCare’s Bifidobacterium infantis which can be given from birth.
  • Whilst it is important to protect your infant from infectious disease, try not to be over zealous about hygiene & use of sterilising cleaning fluids. Your new baby needs to learn about the world.
  • Despite improvements in formula feeds, breast feeding clearly remains the best option. Where not possible, fortify formula with a probiotic (BioCare Bifidobacterium infantis) which also includes prebiotic growth factors.
  • Introduce solid foods very gradually and preferably not before 5-6 months of age.


Bjorksten B (1994) Risk factors in early childhood for the development of atopic diseases. Allergy 49;400-7

Bjorksten B (1999) Environment and infant immunity. Proceedings of the Nutrition Society 58; 729-732

Hamilton G (1999) New Scientist 26th June

Hanson LA & Yolken RH (1999) Nestle Nutrition Workshop series, Vol 42, Nestec Ltd. ‘Probiotics, other nutritional factors, and intestinal microflora.’ Philedelphia. Raven Publishers

Holt PG (1995) Environmental factors and primary T-cell sensitisation to inhalant allergens in infancy: reappraisal of the role of infections and air pollution. Pediatr Allergy Immunology 6;1-10

Murono K, Fujita K, Yoshikawa M, Saijo M, Inyaku F, Kakehashi H, Tsukamoto T (1993) Acquisition of non-maternal enterobacteriaceae by infants delivered in hospitals. Journal of Paediatrics 122;120-5

Wilson AC, Forsyth SC, Greene SA, Irvine L, Hagau C, Howie PW (1998) Relation of infant diet to childhood health; seven year follow up of children in Dundee infant feeding study. British Medical Journal 316;21-25

Zetterstrom R, Bennett & Nord KE (1994) Early infant feeding and micro-ecology of the gut. Acta Paediatrica Japonica 36;562-571