Soy Formula

Breastfeeding provides babies with the best nutrition and is preferred whenever possible. The World Health Organization recommends that infants start breastfeeding within one hour of life, are exclusively breastfed for six months, with timely introduction of adequate, safe and properly fed complementary foods while continuing breastfeeding for up to two years of age or beyond. If you are unable to or have decided not to breastfeed you will need to use a suitable infant formula and follow guidelines for preparation.

Soy formula differs from cow’s milk based infant formulas because:

  • Soy formula has no cow’s milk proteins
  • Soy formula has no lactose (milk sugar).

What should I know about soy formula?

  • There are no nutritional benefits of using soy formula that your baby can’t get from cow’s milk formula.
  • Colicky babies do not show any improvement when fed soy formula.
  • Up to 40% of babies who are intolerant of cow’s milk also develop an intolerance of the soy protein.
  • Soy products contain phyto-oestrogens, which are chemicals that act like hormones. While it’s unlikely that they would have any ill effects on children, at this stage it’s not known for sure.
  • The Ministry of Health has taken a precautionary approach and recommends that soy-based infant formula may affect the function of the thyroid gland.
  • The New Zealand Ministry of Health does not recommend soy-based formula for general use in infant feeding.
  • The only medical indication for soy-based formula is for managing galactosaemia.

If your baby can’t have cow’s milk formula due to an allergy or intolerance, it may be suggested that you try soy formula – although if she’s lactose intolerant you may want to try a lactose free formula first.

  • Using a soy formula will not prevent your baby from developing allergies. If your baby is at high risk of allergies, you should try a HA (hypo-allergenic) cows’ milk formula.
  • Because soy beans are higher in aluminium than cow’s milk, your soy formula fed baby will consume higher quantities of the metal. This is not considered dangerous for healthy babies.
  • There have been concerns about hormones in soy formulas and milks. It’s believed that the levels of these hormones are too low to cause problems.
  • The long-term effects of phytoestrogens in soy-based formula as an infant’s main food source are not known. However, there is ongoing international research under way in this area.
  • If your baby must be on formula, it’s best to leave him/her on cow’s milk formula unless there is a compelling reason to change as it appears that soy formula fed babies have a lower immunity.
  • It is not recommended that premature babies be placed on soy formula until after their due date, as they have more problems with soy formula than on-time babies.

Kidspot is dedicated to the promotion of breastfeeding as the best possible start in life for babies as well as being good for the health and wellbeing of mothers.


Breastfeeding provides babies with the best nutrition and is preferred whenever possible. Good maternal nutrition is ideal for breastfeeding. You should be aware that reversing a decision not to breastfeed may prove difficult. Partially introducing formula could negatively affect your milk supply. Social and financial implications should be considered when selecting a method of feeding. Professional advice should be followed before using an infant formula. Proper use of an infant formula is important to the health of the infant and should only be used as directed.

If you’re worried about breastfeeding, your Well Child nurse or PlunketLine can help.



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