What to Know About Soy Milk Baby Formula

Woman feeding milk to her daughter
ONOKY - Fabrice LEROUGE/Brand X Pictures/Getty Images

The use of soy-protein based baby formula is popular with parents.

Why? Some parents think they will help babies with gas, fussiness, or colic. Unfortunately, switching baby formula usually doesn't help these symptoms. And since soy baby formulas usually cost a few dollars more than cow's milk-based formulas, parents shouldn't be quick to try them unless they are medically indicated.

On the other hand, if your pediatrician thinks that a change to a soy formula is necessary for your baby, you can be reassured that they are just as good as other formulas and are readily available wherever baby formula is sold.

These soy baby formulas include:

  • Enfamil ProSobee
  • Similac Soy Isomil
  • Gerber Good Start Soy
  • Parent's Choice Soy (Wal-Mart brand baby formula)
  • Earth's Best Organic Soy Infant Formula

How popular are these baby formulas?

According to the American Academy of Pediatrics, "Soy protein-based formulas in the United States may account for nearly 20% to 25% of the formula market." While that percentage is probably much less now that so many other baby formulas are marketed to parents, it is still surprising because there are few medical conditions for which a baby should actually need a soy formula. Most newborns and infants who aren't breastfeeding will do just fine on a regular cow's milk-based baby formula, such as Enfamil Infant, Similac Advance, or Parent's Choice Advantage.

When to Switch to Soy Formula

Pediatricians usually recommend soy formula for those babies who need it, including infants with:

  • primary lactase deficiency - a rare condition in which is born without the enzyme to digest the sugar lactose
  • diarrhea and a temporary lactase deficiency (Note: Switching babies to soy formula when they have diarrhea is controversial and usually not recommended)

A soy formula can also be a good choice if a parent wishes to raise their baby as a vegetarian and isn't breastfeeding.

Since there are no completely vegan baby formulas, an organic soy formula may be a good choice for vegan parents wanting to raise their baby as a vegan, too.

When to Avoid Switching to Soy Formula

Soy formula is usually not recommended for infants who have:

  • colic or fussiness, since it will likely not be helpful
  • a cow milk protein allergy, since many of these infants can also be allergic to soy proteins and should drink an extensively hydrolyzed protein formula instead, such as Nutramigen or Alimentum
  • a high risk for food allergies and you are trying to prevent them from getting developing food allergies. If not breastfeeding, these babies should likely drink Nutramigen or Alimentum and not a soy- or cow's milk-based formula.
  • been born premature, since they can lead to decreased bone mineralization, even when the babies are given supplemental calcium.

Unless there is another good reason to start your baby on a soy formula, if you stop breastfeeding before your baby is 12 months old or need to supplement, you can likely just use a cow's milk-based formula instead of a soy formula.

Is Soy Formula Harmful?

Can soy-protein based formula be harmful? It is clear that it can be harmful to premature babies, but the American Academy of Pediatrics states that "There is no conclusive evidence from animal, adult human, or infant populations that dietary soy isoflavones may adversely affect human development, reproduction, or endocrine function."

One of the concerns is that phytoestrogens, especially isoflavones, may have estrogen-like activity. There is also some concern that soy products on a child's immune function and thyroid function, although again, the AAP says that research has been done and has shown any risks or long-term adverse effects of drinking soy baby formula.

One last concern is that soy-protein based formula does have a relatively high level of aluminum as compared to breast milk and cow's milk-based formula. This is not thought to be a problem for term infants, though, but may lead to reduced bone mineralization in preterm babies.though, but may lead to reduced bone mineralization in preterm babies.

Soy Milk Versus Cow's Milk

Like soy baby formula, soy milk is becoming popular with older children, both for children with milk allergies and for parents who are simply trying to avoid cow's milk.

Soy milk can be a good substitute for cow's milk, but keep in mind that soy milk is all reduced fat or low fat and so is not usually a good choice until a child is at least two years old.

Although several other "expert" websites recommend giving "whole" fat soy milk to younger toddlers under two years old, no brands of soy milk have the equivalent amount of fat per serving as whole milk. When looking, keep in mind that whole cow's milk has 8g of fat per serving, while 2% reduced-fat milk has about 5g of fat. Most brands of soy milk only have 4g to 5g of fat per serving or less. In fact, low-fat soy milk only has about 2.5g of fat, which is the equivalent of 1% cow's milk.

Remember that the American Academy of Pediatrics states, "Young children need calories from fat for growth and brain development," and that, "This is especially important in the first 2 years of life." So if you do give your younger toddler reduced-fat milk, be sure to make up for that missed fat in other parts of your child's diet.

What to Know About Soy Formula

Before switching to a soy-based infant formula, parents should keep in mind that there are very few medical reasons that a baby would need to drink soy formula.


American Academy of Pediatrics Clinical Report. Use of Soy Protein-Based Formulas in Infant Feeding. PEDIATRICS Vol. 121 No. 5 May 2008, pp. 1062-1068.

American Academy of Pediatrics. Guide to Your Child's Nutrition.d's Nutrition.

Continue Reading