Soy Formula: A Healthy Or Unhealthy Alternative For Babies?

Soy Formula: A Healthy Or Unhealthy Alternative For Babies?

Leading health organisations from around the world recommend exclusive breastfeeding for the first 6 months and then for breastfeeding to continue alongside suitable solid foods for at least one year.

But for babies who are mixed fed, or formula fed, what formula should a parent choose?

With so many different formulas for parents to choose from, it’s hard to know which one to buy.

According to Australia’s National Health and Medical Research Council (NHMRC), if a baby is not breastfed, “cow’s milk-based formula is suitable for the first 12 months of life unless the infant cannot take cow’s milk-based products for specific medical, cultural or religious reasons, in which case special formulas may be used under medical supervision.”

Cow’s milk-based formulas are the most common formulas on the market. Soy formula is another readily available option.

Is Soy Formula A Good Alternative For Babies?

Here are 3 points to help you make a fully informed decision about using soy formula:

#1: Many Babies With A Sensitivity To Cow’s Milk Protein Are Also Sensitive To Soy Protein

If your baby is sensitive to cow’s milk protein (CMP), one of the following formulas may be suggested by a medical professional:

  • Soy formula
  • Extensively hydrolysed formula
  • Amino acid based (or elemental) formula

However, it’s common for babies who are sensitive to CMP to be sensitive to soy protein too. Therefore, soy formula might not be a suitable substitute for a baby who is sensitive to CMP.

Research has also concluded that soy formula should not be recommended as a method of trying to prevent allergy development in high risk children.

#2: Lack Of Lactose Could Be Detrimental

Soy formula doesn’t contain lactose. This might be beneficial under certain circumstances. For example, there are certain rare metabolic diseases (e.g. galactosemia) that warrant the use of a lactose free formula. The most common formulas used for babies with galactosemia are those made with soy protein isolate.

However, unless there is a medical reason, such as galactosemia, not providing a baby with lactose should be considered carefully. Here are some reasons why.

There are many ways in which breastfeeding helps support brain development. One way is most likely connected with lactose. Lactose readily breaks down into simple sugars, including glucose, which a baby’s developing brain can readily use. In this way, lactose could be important for healthy brain development.

Research has found that electrical brain activity differs between breastfed babies, compared with babies fed either cow’s milk or soy formula. The authors of the study concluded: ‘These variations reflect differences in the organization of basic functional neural networks…. This has the effect of placing these infants on different neurodevelopmental trajectories and indicates a pivotal role of early infant nutrition in setting the general course along which cognitive and brain function development will proceed’.

Soy formula might be suggested if a breastfed baby has a secondary lactose intolerance. However, the solution is not to stop breastfeeding, or to go onto a soy or lactose free formula. These formulas should be recommended only if the baby is already fed formula, or if there are concerns about her growth. You can read more here about lactose intolerance.

#3: Soy Formula Could Carry A Reproductive Health Risk

Many paediatricians do not recommend soy formula for babies under 6 months, due to its phyto-oestrogen content. This is because high levels of phytoestrogen could have negative effects on babies (such as posing a long-term reproductive health risk).

For example, research has found reproductive development deviations, at 4 months of age, amongst babies fed with cow’s milk and soy formula, when compared with partially breastfed babies. It was found that, even at this early stage of development, when compared with partially breastfed babies:

  • cow’s milk formula fed female babies have larger ovaries
  • cow’s milk and soy milk formula fed male babies have smaller testicles.

More research is needed to see how these changes might affect health (including reproductive health) over a lifespan.

When it comes to choosing which formula to use for your formula fed or mixed fed baby, it’s important to be guided by your medical advisor.

Last Updated: April 29, 2016


Renee Kam is mother to Jessica and Lara, an International Board Certified Lactation Consultant (IBCLC), a physiotherapist, author of 'The Newborn Baby Manual' and an Australian Breastfeeding Association Counsellor. In her spare time, Renee enjoys spending time with family and friends, horse riding, running and reading.

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