Firstly some definitions:

• Infant formula refers to products intended for use from birth to six months of age.
• Follow-on formulae are intended from six months to twelve months of age.

The labelling and advertising of these products is regulated by the legislation cited above. After the age of twelve months there is a range of products described as growing-up milks.

Modern infant and follow-on formulae have been developed to replicate the characteristics of breastmilk as closely as possible, and other than maternal antibodies and digestive enzymes this has been achieved with some considerable success. It must be made clear that there is no ideal substitute for breastmilk and whilst formulae may be improved they will never replace all of the benefits of breast milk and breastfeeding.

As well as the usual nutrients, vitamins and minerals you would expect to find in a nutritionally complete milk, there are a number of special constituents found in formulae such as the Aptamil and Cow & Gate ranges of infant milks and follow-on milks.

Recent advances include:

Prebiotic oligosaccharides

Galacto-oligosaccharides (GOS) are found in breastmilk and are now being included in some formula milks together with the plant-derived fructo-oligosaccharides (FOS). They act as substrates for and encourage the growth of intestinal microflora such as bifidobacteria and lactobacilli. This has been shown to inhibit the growth of pathogens and stimulate the immune system, for example improving vaccine response and reducing allergic disease.²

Long-chain fatty acids

There is some evidence that long-chain polyunsaturated fatty acids (LC-PUFAs), also known as omega-3 and -6 fatty acids, such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) are beneficial for visual acuity and, to some extent, brain development.³ They are obtained from the maternal diet in the last few weeks of gestation (shown by a deficiency in pre-term infants), are found in breast milk and are deposited in large amounts in the developing brain. A number of studies have shown that infants fed on DHA-supplemented formula perform better in certain cognitive tests than infants who have not been supplemented. Because of this, advisory groups such as the World Association of Perinatal Medicine recommend the use of infant formulae that contain DHA and ARA.⁴

Nucleotides

Dietary nucleotides, for example adenosine and guanosine monophosphates, are non-protein sources of nitrogen that are important for growth and development of the GI tract and may have beneficial effects on the immune system.⁵ They have been included in some infant formulae for many years and have been shown to reduce the incidence of infant diarrhoea by promoting the growth of the intestinal microflora and thereby inhibiting pathogen growth. There is evidence to suggest that a healthy gut microflora has long-term benefits for the immune system and the prevention of allergic disease.⁶

Whey: Casein ratio

One of the many benefits of breastfeeding is that the quantity and energy content of breastmilk varies according to the demands of the infant. Other than by increasing volume it is difficult to match this versatility by the use of formulae. One possible option is the use of products designed for 'hungry babies' where the ratio of whey protein to casein is adjusted. In breastmilk the ratio of whey protein to casein is 60:40 and this is observed in most infant formulae. Whey forms softer curds and is more easily digested whereas casein takes longer to digest and promotes slower gastric emptying. Products such as Aptamil Hungry Milk and 'Cow & Gate for hungrier babies' have a higher proportion of casein, with a 20:80 ratio. This provides a feeling of fullness for longer and so may satisfy hungrier babies. Note that there is no change in the energy content of these milks.

In addition to these standard formulae there is also a wide range of specialist milks designed for specific medical conditions and feeding problems. The remainder of this module will focus on those conditions and the formulae that can be used to manage them.

² Fanaro S et al. Galacto-oligosaccharides and long-chain fructo-oligosaccharides as prebiotics in infant formulas: A review. Acta Pædiatrica. 2005; 94 (Suppl 449): 22-26.
³ Cheatham C, Colombo J, Carlson S. N-3 Fatty acids and cognitive and visual acuity development: methodologic and conceptual considerations. Am J Clin Nutr. June 2006; 83(6): S1458-1466S.
⁴ Kaletzko B, Lien E et al. The roles of long-chain polyunsaturated fatty acids in pregnancy, lactation and infancy: review of current knowledge and consensus recommendations. J Perinat Med. 2008; 36(1): 5-14.
⁵ Singhal A, Macfarlane G et al. Dietary nucleotides and fecal microbiota in formula-fed infants: a randomized controlled trial. Am J Clin Nutr. June 2008; 87(6): 1785-1792.
⁶ Bourlioux P, Koletzko B et al. The intestine and its microflora are partners for the protection of the host: report on the Danone Symposium 'The Intelligent Intestine', held in Paris, June 14, 2002. Am J Clin Nutr. October 2003; 78(4): 675-83.