Infant formulas these days boast intimidating new ingredients such as nucleotides, AA, DHA, Choline and Taurine, each claiming health and developmental benefits.

'They are trying to mimic mother's milk, but as we know, mother's milk is best and it has complex nutrients,' said Sister Kang Phaik Gaik, a lactation consultant at Mount Alvernia Hospital.

Sister Kang is a strong advocate of the World Health Organisation's recommendation that babies be exclusively breastfed for the first six months.

For some mothers like Sharmaine Poh, 32, who delivered twin girls a month ago, infant formula is a necessity. 'I don't have enough breast milk for two babies, so I am alternating the twins on breast and formula,' she said.

Ms Poh said she was initially confused by the number of nutrients on offer, wondering how to choose the right one. 'In the end, I went for a reliable brand that my mother said I had liked as a baby. My girls seem comfortable with it, so it's good,' she said.

According to leading paediatricians in Singapore, most infants who are not breastfeeding exclusively should be given a cow's milk-based iron-fortified formula.

Most formulas in the market today have cow's milk as their main ingredient. The protein in the milk is significantly altered to make it easier to digest.

Other types of formula milk include soy-based formulas for babies allergic to cow's milk and lactose-free formulas for babies who are allergic to milk.

Ms Bibi Chia, dietitian and director of Eat Wise, said the important things to consider when buying formula are pricing, nutrients and whether the baby develops any allergies, diarrhoea or constipation after taking a particular formula.

Many parents find that they need to try one or two brands before they find one that suits their baby.

According to Ms Chia, formula milk should be as close as possible to breast milk. So, anything extra is not needed.

'There are optional ingredients, such as Taurine, Nucleotides, Phospholipids, LU-PUFA (DHA) and prebiotics, that are known to have some benefits,' Ms Chia added.

The ingredients are explained below:

Taurine: This is an amino acid present in breast milk and is supposed to increase energy.

DHA and AA: These are the main fatty acids found in breast milk. They are reported to be key in brain and retinal development. More studies are needed to confirm its safety and benefits. For the time being, infant formulas should not have DHA exceeding 0.5 per cent of total fat content and must have similar amounts of AA.

Nucleotides: These are the building blocks of DNA and RNA. They may improve the absorption of iron, improve gut bacteria and enhance baby's immune system. However, the benefits and safety of these need more long-term study. Infant formulas should not contain more than 5mg/100kcal of total nucleotides.

Probiotics: These are beneficial bacteria that are usually present in a healthy digestive tract.

Prebiotics: These are non-digestible components of carbohydrates that help feed specific good bacteria. For instance, a sugar-like substance present in bananas, called fructo-oligo-saccharide, can help support the growth of good bacteria.

This article was first published in Mind Your Body, The Straits Times on Apr 16, 2008.