What to Know About Soy Milk Baby Formula

Woman feeding milk to her daughter
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The use of soy-protein based baby formula is popular with parents because some parents think this food will help babies with gas, fussiness, or colic. However, switching baby formula usually doesn't relieve 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

Soy-based formulas remain popular with parents. According to the American Academy of Pediatrics, "Soy protein-based formulas in the United States may account for nearly 20 percent to 25 percent of the formula market." This rate may be higher than it needs to be because there are few medical conditions for which a baby actually needs 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:

  • Galactosemia
  • Primary lactase deficiency—a rare condition in which is born without the enzyme to digest the sugar lactose
  • Diarrhea and a temporary lactase deficiency (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 parents wish to raise their baby as a vegetarian and the mother isn't breastfeeding. Since there are no completely vegan baby formulas, an organic soy formula may be a good choice for vegan parents who want 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?

Soy formula 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. Some experts question the effect that soy products influence on a child's immune function and thyroid function, although again, the AAP says that research has been done and has not shown any risks or long-term adverse effects from drinking soy baby formula.

One last concern is that soy-protein formula contains a relatively high level of aluminum as compared to breast milk and cow's milk-based formula. This exposure is not thought to be a problem for full-term infants, 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 soy milk is all reduced fat or low fat and so is not usually a good choice until a child is at least 2 years old.

Although some poorly sourced websites recommend giving whole-fat soy milk to toddlers under 2 years old, no brands of soy milk have the equivalent amount of fat per serving as whole milk. Whole cow's milk has 8g of fat per serving, while 2 percent 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 percent cow's milk.

The American Academy of Pediatrics states that "young children need calories from fat for growth and brain development," and that "this is especially important in the first two years of life." So if you do give your toddler reduced-fat milk, make up for that missed fat in other parts of your child's diet.

Sources:

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.

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