Soy Formula & Constipation in Infants

Soy formula contains protein derived from soybeans. The link between soy formula and constipation is a much debated topic among parents and even pediatricians, according to Melvin Heyman, M.D., professor of pediatrics and chief of the division of pediatric gastroenterology at University of California, San Francisco. That’s because soy formula seems to help constipation in some babies and bring on constipation in others. There are several reasons why soy formula may help get things moving – or not.

Constipation in Infants

Constipation in infants refers to lack of a bowel movement. The signs of constipation in infants include: three or more days without a stool, pain or crying during a BM, and inability to pass a stool after straining longer than 10 minutes, according to, the official website of the American Academy of Pediatrics.include:

  • The signs of constipation in infants include: three or more days without a stool
  • pain or crying during a BM,
  • inability to pass a stool after straining longer than 10 minutes
  • according to
  • the official website of the American Academy of Pediatrics

The exception is breast-fed infants older than 1-month-old. Inadequate intake of breast milk often imitates constipation in these babies. Keep in mind that grunting or straining while pushing out a stool is normal in young infants, according to It’s also common for non-constipated infants to become red in the face during straining. However, formula-fed babies who don’t have a BM after five days are probably constipated, according to Heyman.

Soy Formula Benefits

Mother holding feeding baby

Infant Constipation & Vitamins

Learn More

Heyman says that constipation in infants can sometimes be formula-related, so switching to a soy formula may help some babies. indicates that because soy formulas contain soy protein and carbohydrates that are different from milk-based formulas, they are sometimes recommended for babies unable to digest lactose, the main carbohydrate in milk-based formulas. Many babies have brief periods when they can’t digest lactose, particularly after bouts of diarrhea. Some parents believe soy formula may ease colic or fussiness, though states there’s no evidence of that. If you wish to raise your child as a vegetarian, soy formula has the benefit of containing no animal products.

Soy Formula Problems

Soy formula can make stools harder, worsening or causing constipation in some babies, according to Heyman. Another problem with switching to a soy formula: Some babies may be allergic to soy. Giving these babies soy formula could actually cause digestive problems, including constipation. According to Dr., about 20 percent of babies with a cow’s milk allergy will also be allergic to soy. Both these allergies are typically outgrown as infants or toddlers. Some soy formulas are lower in iron than milk-based formulas. Parents may choose soy formula for this reason because taking iron supplements causes constipation in adults, but recommends iron-fortified baby formulas to prevent anemia. There’s no evidence that using a low-iron supplement will help ease constipation.

Additional Considerations

Mother holding feeding baby

The Difference Between Nutramigen & Alimentum

Learn More

For babies allergic to soy or milk-based formulas, hypoallergenic formulas are available. Some formulas are fortified with probiotics, healthy bacteria that may ease constipation and other digestive problems. Other constipation remedies may be worth a try. If your baby seems to be constipated, Heyman suggests giving your little one extra water or offering a bottle of diluted prune juice once or twice a day. Once your baby starts on solid food, typically at 6 months of age, cereal and baby foods with peas, beans and other vegetables will help get things moving because they contain constipation-easing fiber.