INFANT NUTRITION: Baby’s Best Milk

Infant nutrition has long been viewed as important. Optimal infant nutrition enables infants to grow and develop successfully. It ensures good physiological programming early in life which favours a lower disease risk in later life. Much has been said about the impact of programming on cardiovascular, diabetes and metabolic syndrome.

In contrast, there has been relatively little discussion on how early diets modulate gut function. A healthy, functioning gut is crucial in the defence against external pathogens and in the maturation of the immune system. Infants are vulnerable to infection because their guts are immature and they are in the early stages of building up immunity to common pathogens.

However, breast-fed infants have a generally lower risk for developing diseases because of the presence of prebiotic oligosaccharides in human milk. This opens new perspectives for food and beverage innovators aiming to direct their products towards infant health. Indeed, there is growing evidence that nondigestible oligosaccharides like insulin and oligofructose have a special role to play.

The infant gut
The foetal gut is sterile but birth leads to rapid colonisation by bacteria present in the immediate environment, such as E. coli and Streptococci or by beneficial bacteria like bifidobacteria and lactobacilli. The evolution of the gut flora depends on how infants are fed. In breast-fed infants, pathogenic bacteria are rapidly replaced by Bifidobacterium species.

In formula-fed infants, pathogens proliferate alongside more beneficial species resulting in a more varied and complex flora. Bifidobacteria are normally the most prevalent organism in the infant gut, although breast-fed infants have 10 times higher levels of the beneficial bacteria than formula-fed infants. The ability to ferment inulin and oligofructose is evident from an early age and improves throughout weaning.

The composition of the microflora of the infant gut has a major impact on resistance to infection. Several properties of bifidobacteria and lactobacilli contribute to this effect. Fermentation of prebiotic oligosaccharides such as inulin and oligofructose creates metabolites, such as lactic and acetic acids, which have direct antimicrobial effects. These also lower the pH of the gut lumen, detering external pathogens from taking up residence as they tend to favour less acidic conditions. In addition, there exists a strong cross-talk between the endogenous microbial flora and the immune system (gut associated lymphoid tissue) influencing its development during infancy.

Infant feeding and health
The golden standard for infant feeding is, and always will be, human breast milk. Yet a minority of infants are breast-fed to the recommended age of six months. With that in mind, there is a need to determine the key constituents of breast milk and apply best practices to formula milk and weaning foods.

While it may be impossible to replicate the complex nature of human breast milk, some beneficial components can be mimicked. One important example is oligosaccharides (prebiotics). These nondigestible carbohydrates, which represent the third component of human milk after lactose and lipids, constitute about 12 grams per litre of breast milk.

Several investigations have shown that oligosaccharides are responsible for the well-known bifidogenic effects of human milk. In comparison, cow’s milk (used as the basis for infant formulae) contains very few oligosaccharides (less than one gram per litre) and these have a different structure from those present in human milk.

In this perspective, supplementation of infant formula with oligosaccharides as a food ingredient might offer an interesting approach to supporting gut health in infants, children and also adults. While commercial oligosaccharides are not identical to those found in human milk, research shows that they are very effective at promoting colonies of bifidobacteria and lactobacilli.

The test of a prebiotic is whether it is resistant to digestion and absorption in the upper intestine, can be fermented by colonic bacteria, and if it can selectively stimulate the growth and metabolic activity of beneficial bacteria. To that end, there are few ‘true’ prebiotics and the properties of inulin and oligofructose are most extensively studied and described.

Several studies have shown that the supplementation of infant formulae with inulin, oligofructose, galacto-oligosaccharides or combinations of these selectively promotes colonic bifidobacteria and lactobacilli. A change in faecal consistency towards softer stools and a higher stool frequency is also observed.

Two studies compared the proportion of bifidobacteria in the stool flora of newborn infants fed with a standard formula in one group, with another supplemented with a mixture of inulin and GOS. In the prebiotic group, gut bifidobacteria increased from 31 percent at baseline to 59 percent at six weeks of age, whereas no signifi cant change was observed in the standard group. At six weeks of age, the percentage of bifidobacteria in the prebiotic group was close to the 79-percent levels reported for breast-fed infants.

The gut flora of older infants can also be modulated by prebiotics. In one study, a prebiotic-containing formula (inulin and GOS) was introduced to infants aged four to 12 weeks fed for at least four weeks with a standard infant formula. After six weeks on the prebiotic formula, the numbers and species of gut bifidobacteria were similar to those typically found in breast-fed infants.

Tolerance and safety
Infants are susceptible to infection both from the introduction of new pathogens, such as from improperly washed milk bottles, and the overgrowth of pathogens normally residing in the infant gut, such as harmful clostridia species. Breast-fed infants experience significantly fewer gastrointestinal, respiratory and urinary infections than formula-fed infants. Part of the reason may be the presence of oligosaccharides in human milk.

The impact of prebiotics may go well beyond the gut. Several studies have suggested that the make-up of intestinal flora can influence atopia (susceptibility to allergy) and help optimise immune function. bifidobacteria have been associated with a better balance between Th1 and Th2 cells, which encourages normal immune responses.

Certainly, the guts of atopic infants have been found to contain fewer bifidobacteria and more clostridia than non-atopic infants. In addition, early gut colonisation with beneficial bacteria accelerates the maturation of the secretory IgA response and possibly brings about earlier innate immunity to microbial stimulation.

Prebiotic oligosaccharides are in general considered safe. In none of the trials with children were there any signifi cant signs of gastrointestinal intolerance such as flatulence, abdominal discomfort or increased purge. Studies on the supplementation of a formula for pre-term and term infants with a mixture of inulin and GOS did not fi nd any influence on weight gain or length increment. Studies have shown that prebiotic oligosaccharides appear to be well tolerated by both infants and children.

Prebiotics represent a safe, effective way of increasing the counts of bifidobacteria and lactobacilli in the intestinal flora of infants and children. Increased levels of beneficial bacteria help infants and children resist infection and may aid in the optimal development of their immune system over time.

Few oligosaccharides are true prebiotics and extensive evidence exists for inulin and oligofructose. These can be used as ingredients in a wide variety of food and beverage products and offer manufacturers an innovative means of improving current infant feeding products.

www.orafti.com