Soy-based formula for babies may affect their reproductive systems

Soy-based formula for babies may affect their reproductive systems

This research shows that soy-based formula for babies can cause faster development, and this was especially true for baby girls. Read on to know more.

Soy-based formula for babies are chosen by parents when their little ones are sensitive or allergic to cow’s milk protein. However, a recent study by the National Institute of Environmental Health Sciences (NIEHS), U.S., has unveiled a startling health effect of soy-based formula for babies.

They discovered that feeding your infants soy-based formula, as opposed to cow-based formula or breast milk, may create differences in their reproductive cells and tissues. 

Let’s find out more about this study and its findings. 

Should you say ‘No’ to soy-based formula for babies? 

Researchers found that soy formula contains a high concentration of plant-based estrogen. This can bring about subtle effects in estrogen-responsive tissues in soy-fed infants, which may or may not have long-term health effects.

Virginia A. Stallings, MD, director, Nutrition Center at Children’s Hospital of Philadelphia (CHOP), who co-wrote the study with NIEHS said, “Because this formula is the sole food source for many babies in the first six months of life, it’s important to understand the effects of exposure to such compounds during a critical period in development.”

Estrogen in itself is also particularly important because infants do have phases of growth where they are sensitive to estrogen. Thus, there’s a higher chance that infants will experience the effects of plant-based estrogen compared to adults.

However, Stallings does note that these differences were subtle and not alarming. But only further investigation can prove the long-term effects of “exposure to estrogen-like compounds found in soy-based formulas.”  

Why plant-based estrogen may not be good for your baby

According to the study, many mothers who are unable to breastfeed or give cow-based formula, instead opt for soy-based formula for babies. This could be due to difficulty with breastfeeding or the baby being lactose intolerant.

But what they do not realise is that soy-based formula may have high amounts of genistein, an estrogen-like compound.

“Like other estrogen-mimicking chemicals found in the environment, genistein can alter the body’s endocrine system and potentially interfere with normal hormonal development,” CHOP stated in its release. That is why soy-based formula for babies may not be a good option. 

Baby girls were more susceptible to faster hormonal development

To further understand the level of hormonal development, the researchers enrolled 410 infant-mother pairs. But only 283 pairs completed the study.

Out of these, 102 infants were exclusively fed soy formula, 111 were given cow-milk formula, and 70 were on breast milk. And, about 50 percent of the infant participants were girls. 

Stallings clarifies, “This was an observational study, not a randomized trial. All of the mothers had decided on their feeding preferences before we enrolled them in the study.” 

The team studied three outcomes:

  1. Maturational index (MI), which was based on epithelial cells taken from the baby’s urogenital tissue
  2. Ultrasound measurements of uterine, ovarian and testicular volume, and breast-buds
  3. Hormone concentrations through blood tests

Stallings noted, “The main differences we found related to different feeding preferences were among the girls.”

soy-based formula for babies

Baby girls studies in this research had higher developmental trajectories. | Image courtesy: stock image

There were three changes that they noted. 

  • As compared to girls who were fed cow-milk formula, those who were given soy-based formula showed higher developmental trajectories
  • Such babies also had higher vaginal cell MI
  • Their uterine volume decreased more slowly (as compared to babies fed cow-based formula)

Incidentally, the study team found similar differences between breastfed and soy-fed girls.

“We don’t know whether the effects we found have long-term consequences for health and development, but the question merits further study,” said Stallings. She also added that while many mothers may prefer soy-based formula, they still recommend breastfeeding. 

“For new and expectant mothers deciding on how to feed their infants, as always, we strongly support breastfeeding, as recommended by the American Academy of Pediatrics (AAP),” she categorically stated.

But what if you are unable to produce enough breast milk? 

How to naturally increase breast milk supply  

As stated in our previous article, milk production works on the demand and supply principle. When your baby demands milk, your body will produce milk to fulfill his need.

However, sometimes your body needs an extra push in order to produce enough milk to sustain your baby’s demand. 

In that case, you can try the following.

  • Milk boosters. You can increase milk supply naturally by including galactagogues (breastmilk boosters) in your diet. These include fenugreek seeds, herbal tea, nuts like almonds and walnuts, and dried figs. Lactation cookies also contain many of these galactagogues.
  • Pumping. You may have to start pumping using an electric breast pump. Ideally, you should pump every three hours and even during the night. So pump for five to six minutes on a low to medium setting on the pump. Then, follow it up with a breast massage. Afterwards, pump for five to six minutes again.
  • Donor breast milk. When none of these natural ways work, you can consider donor breast milk.


Other facts about soy-based formula for babies

When are soy-based formula for babies recommended?

According to the AAP , soy-based formula for babies pose no danger to them and are as nutrient-rich as milk-based formula. In particular, soy-based formula for babies is suitable for full-term infants who aren’t receiving enough nutrients from breast milk, and also for full-term infants:

  • affected by galactosemia. Galactosemia is a condition where a baby is unable to properly burn off lactose, the sole sugar milk contains, or a part of lactose called galactose.
  • who have inherited lactase deficiency (very uncommon case)
  • who have a history of transient lactose deficiency.
  • that are known to have an allergic reaction to cow’s milk but not soy-based proteins.
  • that have parents who want them to eat a vegetarian-based diet .

If you’re baby has lactose intolerance, it may also be a good choice to choose lactose-free soy-based formula for babies. Still, the AAP advises to limit the usage of lactose-free soy-based formula for babies, as only a small number of babies require complete avoidance of lactose. 

Soy-based formula for babies

Soy-based formula for babies doesn’t offer any extra advantage compared to milk-based formula. | Image Source: Stock Photo

When should I not use soy-based formula for babies?

Soy-based formula for babies isn’t suitable for:

  • infants who experienced premature birth and weigh under 1800 g. 

  • averting colic or allergic reactions. The AAP states that soy-based formula for babies do not help to treat or prevent colic, or the wailing and irribitality accompanying it. Sucrose and fibre in soy-based formula for babies can calm a colicky baby, but research illustrates that soy-based formula for babies isn’t as good as formula made from cow’s milk.

  • babies who suffer conditions when exposed to cow’s milk, like enterocolitis or enteropathy.

The AAP advises that drinking soy-based formula for babies an addition to breast milk doesn’t bring any additional benefit compared to milk-based formula. That is, except for infants who have the conditions above.

Other substitutes for soy milk if your baby cannot tolerate cow’s milk or breastfeed

The AAP recommends feeding these infants the following, instead:

  • amino acid formulations. That’s because amino acids make up protein. Amino acid formulations also provide other ingredients which infant formulas have now so that you’re child can receive the best form of nutrition.
  • milk-based formula that is lactose-free cow.
  • hydrolysed protein formula, which contains a few milk-based chemicals. Scientific studies have shown that 10% to 14% of babies who have an allergic response to cow’s milk may also experience the same reaction to soy protein. 

If all fails, consult your baby’s paediatrician for support and guidance.


Sources: Science Daily, Medicalxpress, CHOP, WebMD, NIEHS,

ALSO READ: Contamination of formula milk: Why all parents must know about this

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Written by

Deepshikha Punj

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