Soy baby formulas has become an increasingly popular alternative for traditional dairy based formulas. There are many reasons soy and other plant based foods and beverages have soared in approval, especially amongst vegan households.
What are the pros vs cons of soy baby formula? The nutritional profile and lower environmental impact of soy formula is a leading claim for support. However, as much as plant based foods are praised, expert don’t always recommend soy formula as a suitable alternative for babies or infants.
This article seeks to explore the pros and cons of soy baby formula. Answered below are frequently asked questions about the positives and negatives of soy formula, and what concerns to be aware of when feeding soy products to a baby.
Consult with a pediatrician or physician to see if soy baby formula is right for your child. A professional will be able to analyze your specific case and better determine what is right for your child’s diet.
Should I switch my baby to soy formula?
No, experts don’t always recommend switching a baby to soy formula unless there is a good reason to make the switch. A few examples might be your baby has a dairy allergy or lactose sensitivity, you are unable to provide breastmilk, or your family and household are strictly vegan.
There are, of course, many other great reasons, but we don’t think the decision to switch to soy formula should be taken lightly.
Switching to soy formula may cause hormone imbalances, and itself is a common allergen. Experts typically recommend breastmilk or dairy based formulas for a baby.
Consult a pediatrician or nutritional specialist to help create a plant-based or milk alternative diet that is specific for your baby.
Why is soy formula not recommended for babies?
Soy formula is not recommended for babies because it high in isoflavones. This is a plant component possessing the same structure as the estrogen hormone.
Estrogen is a vital hormone in human development, for both males and females, but is typically produced in proper amounts in the body. Adding excess estrogen, or any hormone for that matter, can cause developmental issues and have longer term impacts on your baby’s health.
There have been many scientific studies that track the impact of excess or imbalanced hormones on babies and most offer caution. Current thinking is that soy based formula may have a detrimental long term effect if used as the primary source of calories for a baby [1, 2, 3].
Consult with your pediatrician or nutritional specialist if you have concerns about the overconsumption of soy products, or if soy based formulas are the only option. Soy based formulas can be a good supplement to a baby’s diet, but you will need to carefully watch how much they eat [4, 5].
Is soy formula hard to digest?
No, soy formula is relatively easy to digest, especially compared to proteins derives from animals.
Many babies, and also adults, are lactose intolerant, which would make dairy hard for the body to handle. Even if you are lactose tolerant, you might find soy easier to digest, and the same should be true for babies.
Why is my baby constipated on soy formula?
Constipation is often an issue in babies of all ages, whether or not they are on soy formula.
Constipation is having less frequent bowel movements than normal, larger or hard bowel movements, frequently accompanied with pain or difficulty to pass.
Normal bowel movements in babies largely relies on their age and diet, but ~3 normal/soft bowel movements is normal for young babies.
Introducing any new type of food can alter the amount, and introducing dairy and/or plant based milk like soy formula might decrease the amount of movements compared to breast milk. You might expect 2-3 movements per day, but this also depends on the type of formula consumed.
Do babies gain weight on soy formula?
No, babies fed soy formula do not gain more weight than babies fed on breast milk or dairy based formula.
Soy contains phytic acid, which can prevent the absorption of certain minerals, and may lead to weight loss amongst other deficiencies. However, if you are giving your child soy formula in addition to other foods, it may be a nice complimentary source of certain nutrients.
Baby weight gain can be tricky and is often worrisome. Soy formula is ok if it is your only choice, but there are other options to consider to counteract some of the worrisome side effects of consuming too much soy.
Soy formula side effects
Although there are benefits to introducing soy formula to a baby’s diet, soy formula also has negative side effects. Among the side effects to be aware of include;
- Anti-nutrients: Soy formula contains certain inhibitors like phytic acid which are perceived to effect digestion and absorption. These compounds may impede growth and health development in your baby [6].
- Lectins and saponins: Lectins and saponins usually can be found in soy. These compounds can cause leaky gut and gastrointestinal issues and may negatively impact the immune system [7].
- Colic and Oligosaccharides: The presence of oligosaccharides in soy formula may lead to increased production of gas and causes colic in babies [8].
- Nutritional deficiencies: Research has shown that soy formula can lead to vitamin deficiencies in babies if it is the sole source of nutrition. The reason is because soy is less caloric than milk based formula, so your baby might consume less and certain components of soy may block absorption of key minerals and vitamins [9].
- Phytoestrogens: Although there is no definitive evidence that phytoestrogens have toxic effects on infants fed a diet of soy based formula, concern has been raised from the results of specific animal studies [10].
Benefits of soy formula
Soy formula is not all bad! We actually think it could be a great supplement to your baby’s diet if used judiciously. Some of the benefits your baby will enjoy from soy formula can be
- A nutritious substitute: Soy formula is cholesterol-free and low in saturated fat.
- Great source of protein: Soy formulas usually incorporates complete proteins. It actually possesses all the vital amino acids required for growth, making it a wholesome protein source. For this reason, it is regularly enjoyed by vegetarians and kids who cannot consume dairy milk.
- Lactose-free: Unlike cow milk and other plant-based milk, soy formula does not contain lactose. Lactose intolerance normally leads to symptoms like gas, vomiting, constipation, irritability, abdominal pains, diarrhea, and breathing issues.
- Additional and Added nutrients: Soy formula contains soy protein isolates and amino acid L-methionine. It is often fortified with all the crucial nutrients to support child development and growth that they might not be getting from other foods. Soy formula often has added nutrients include DHA, lutein, calcium, AA, and prebiotics.

Pros vs Cons Soy Baby Formula: Conclusion
Soy formula is undeniably safe for many healthy kids when used in moderation. It can be a great option if you baby has dietary restrictions like allergies or lactose intolerance.
However, the soy component may cause detrimental effects to your child’s health. Experts don’t always recommend switching to soy formula as the sole source of nutrition for children, especially under 5 years of age when diet is such an important factor for growth and development.
The reason experts don’t recommend soy based formulas is because there have been many studies suggesting soy products can have a long term detrimental impact on overall health. Soy contains isoflavones that are linked to increased levels of estrogen in people who consume large quantities of soy.
Estrogen is a vital hormone to our health, but our bodies are usually able to produce the right levels of estrogen to function properly. Excess estrogen, influenced by large amounts of soy, soy milk, or soy formula, can cause imbalances with negative effects.
There are pros and cons to consuming soy baby formula. There appears to be research supporting both sides of the fence, so this is something that you and your pediatrician should take into account when developing a diet plan for your child.