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Side effects of soy baby formula

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Babies that find it difficult to tolerate dairy-based formulas occasionally have an easier time with soy based baby formula. Soy baby formulas are a common substitute to dairy based, especially for those with lactose intolerance or strict vegan diets. 

What are side effects of soy baby formula? Unfortunately, research has proven that soy based formulas may have a negative impact on developing babies due to the high estrogen levels, aluminum toxicity and anti-nutrients like phytic acid associated with them. 

This means, soy baby formulas should be consumed in moderation and not be as the main source of nutrition for your baby. 

In this article, we explore the side effects of soy baby formula. Answered below are frequently asked questions about soy baby formula and possible side effects to be aware so that you can give your child the proper nutrition they need to grow and develop.

Be sure to speak with a pediatrician or nutritional specialist when deciding on the type of formula to give your baby. Diet has such a large impact on the early stages of growth and development, so get a professional opinion when making the decision about your child’s diet.

Does soy baby formula have estrogen?

Soy baby formula is highly concentrated with plant-based compounds that are similar to estrogen or thought of as plant estrogen. It is crucial to understand the impacts of increased exposure to these compounds since soy is a very common ingredient in baby formulas, and soy formula might also be one of the few options for babies experiencing allergies or lactose intolerance. 

Soy protein has a a high level of genistein, a soy derived compound similar to estrogen. Genistein can potentially alter normal hormonal development and harm the body’s endocrine system, similar to other estrogen-like compounds. 

Lab studies and research suggest that high genistein levels can lead to all sorts of issues including developmental issues [1, 2].

More research needs to be done on the impact directly to babies, but some experts think the evidence is compelling enough to avoid giving soy to babies. 

Babies who are regularly given soy baby formula risk developmental issues consistent with the effects of estrogen exposure. Estrogen exposure, or large amounts of soy, can negatively impact both boys and girls. 

Limiting the total amount of soy baby formula given to any baby is a possible course of action to consider.

Do babies eat more on soy formula?

No, babies do not eat more on soy formula. Soy milk does not have all the nutrients a baby will need to fully develop, and does require the formula to be fortified to higher levels for wholesome micro and macro nutrition. 

Therefore, soy formula should be created with the right amounts of nutrients needed for babies to grow. Babies should not need to eat more soy formula compared to regular formula or milk, and appropriate serving sizes will be labeled on the packaging.

Soy baby formulas typically have similar calories and vital nutrients as other kinds of baby formulas. Although baby formulas go through rigorous scientific processes before reaching the shelves, not all formulas are the same. 

Many brands also have multiple different formulas that are designed for specific needs. Be sure to check with your pediatrician or nutritional specialist for the specific brand and formula that is best for your baby in their given stage of growth and development. 

Does soy formula make babies poop more?

Every infant is unique, but in general you can expect your baby to poop one or three times per day when they are consuming soy formula. It shouldn’t worry you so long as your infant is thriving well and is not struggling when pooping. 

The consistency and color of the poop are more important compared to the frequency to movements. However, if your baby doesn’t poop for up to 5 days, it can be due to constipation and you should consider contacting a pediatrician.

Potential Effects of Soy Formula

Plant based formulas are commonly thought of as substitutes for dairy-based formulas. Many babies have dairy allergies or are lactose intolerant, and need an adequate substitute for adequate nutrition. 

Some experts have determined that soy based baby formulas should not be your first option, rather can be used to supplement the alternative you find.

If you are concerned about soy baby formula, here are a few possible side effects to be aware of when making your choice:

Shifting Allergies

Switching to soy baby formula may not solve a baby’s allergy problems as research shows at least a 10-15% chance of cross-reactivity in soybeans and dairy proteins [3, 4]. 

The majority of babies who don’t tolerate dairy proteins tend to also be allergic to soy protein. If your baby has a dairy allergy, be cautious when introducing them to soy formula for the first time as you might just be shifting allergies.

The symptoms of soy allergies include skin irritation, stomach pain, colicky behavior, and diarrhea. If you notice a severe reaction, seek expert care immediately, and for moderate side effects you may still want to remove soy from your child’s diet. 

Hormonal Imbalance

Hormonal side effects linked to soy baby formula are the most problematic. 

Soy products have compounds known as phytoestrogen, which have been linked to increased amounts of overall estrogen in a child or baby’s body. These compounds can affect many different natural processes in a developing body and research suggests they can be linked to early puberty or long term diseases. 

They can also lead to stunted growth or other developmental issues in young children. Research is not conclusive, but there seems to be cause for concern in animal studies that have been previously conducted [5, 6, 7].

Gastrointestinal Effects

Soy has been known to cause stomach irritation, bloating, or digestion issues in adults. The same can be said for children and babies, and there is evidence to show that it might have a large effect on younger people [8, 9]. 

We encourage you to speak to a pediatrician or nutritional specialist before introducing soy formula to your baby. 

Can soy formula hurt my baby?

Soy formula may be harmful to babies in both the short and long term. Some experts do not recommend switching completely to soy formula, and that it only be used as a supplement if needed. 

A few reasons why soy based baby formula is always not recommended: 

Trypsin Inhibitors

Soybeans contain many trypsin inhibitors that can hinder the absorption of vital nutrients to your child’s body. 

Trypsin is used in the body to predigest proteins and allows for full absorption of proteins. Trypsin inhibitors can interfere with the digestion process and leave proteins undigested.

Prevent Nutrient Absorption

Soy formula contains phytic acid, which inhibits the absorption of zinc, calcium and other minerals. 

Zinc is used in many neurological processes and brain development. Calcium is imperative for bone structure, and both are vital in early development.

Why is soy formula bad?

There are a few reasons people consider soy formula bad for babies. More research needs to be done, but a few of the reasons include aluminum toxicity, phytoestrogen and phytic acid.

Let’s discuss a bit more about why soy formula may be bad for babies: 

Aluminum Toxicity

Soy-based formula may contain a high amount of aluminum due to heavy metals present in industrialized farming. The content of aluminum in breastmilk is significantly lower than that of soy-based formula. 

The high toxicity of aluminum is linked with a high disposition in bones and the central nervous system, and it can also lower renal functioning in babies with renal failure and preterm infants.


Drinking a lot of soy baby formula increases the amount of estrogen-imitating compounds. 

When you expose your child to estrogen-like chemicals, either in the womb or during early development, there is the possibility of adverse effects during adulthood. For infants, soy formula may significantly increase the amount of estrogen levels. 

Phytic Acid

Soybeans contain a high amount of phytic acid, which hinders the absorption of essential minerals, including iron, calcium, zinc, and magnesium. 

These minerals are vital for functionality and development of the nervous system and brain. Too much soy formula can lead to nutrient deficiencies resulting in poor growth for your baby. 

Soy baby formula side effects

Soy Baby Formula Side Effects: Conclusion

If you are a pregnant mother thinking about different ways to feed your infant, we strongly recommended you consider breastfeeding. However, if you are a mother who opts for baby formula, then using a dairy based formula or other non-soy alternative may be best. 

In general, there seems to be concern about the overconsumption of soy products. There are a number of reasons why, but namely due to phytoestrogen, potential allergy crossover and gastrointestinal aggravation

Soy formula has been shown to have lasting affects on babies and can disrupt early development. While it may be alright in moderation, some experts suggest soy formula not be the first alternative to breastmilk or other formulas. 

Consult with a pediatrician or nutritional specialist for help selecting the best formula and diet plan for your baby. A babies overall growth and development is highly impacted by their diet, and choosing the right foods are important.

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