Lactose-reduced Infant Formula Is Associated With Increased Obesity Risk

A new study finds that babies who use this kind of formula have a greater risk of obesity at age two, but some formula-fed babies don’t need this type at all. Here’s what you should know.

Preparing bottle with formula
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Lactose-reduced infant formulas are popular choices for parents, but new research published in the American Journal of Clinical Nutrition suggests these formulas may be associated with a higher risk for obesity in early childhood.

In the study of more than 15,000 formula-fed children, those who were given lactose-reduced formulas made with corn syrup solids in the first year had a 10% higher obesity risk at age 2 than those who had standard formula. Rapid weight gain in the first two years of life ups the risk of obesity later on and kids with obesity are more likely to have obesity as adults.

These are important findings since many caregivers seem to be choosing lactose-reduced formulas. One study from University of Rochester found that 55% of all powdered infant formula purchased between 2017-2019 was lactose-reduced.

This increase could be because labels of lactose-reduced formulas often include words like "sensitive," "gentle," and "soothe"—terms that aren't regulated but may be especially appealing to parents grappling with fussiness.

It's also important to note that there are just three main carbohydrates used in most infant formula: lactose, glucose-rich carbs like corn syrup, and to a lesser extent, sucrose. So if a caregiver wants a formula without lactose, there aren't a lot of alternatives.

Do Babies Need Lactose-Free Formula?

A lot of the babies who use this type of formula may not actually need it. Babies are born with a supply of lactase, the enzyme needed to digest lactose, the carbohydrate in cow's milk (human milk is naturally rich in lactose too). So lactose intolerance isn't typically an issue yet.

Some exceptions: Babies who are born premature are at higher risk for something called developmental lactase deficiency and can't digest lactose for a short period of time, according to the American Academy of Pediatrics. Rates of premature births are highest for Black infants. There's also a rare condition called congenital lactase deficiency, where babies are born with lactose intolerance.

A small percentage of babies will have an allergy to cow's milk and need a hypoallergenic formula with partially or fully broken-down proteins. These formulas are also lactose-free.

"Few babies need lactose-reduced formula," says Shannon Whaley, Ph.D., co-author of the study and director of research and evaluation at Public Health Foundation Enterprises WIC, a program of Heluna Health in California. "If a baby is fussy, it's unlikely because of lactose." Lactose intolerance typically shows up in children ages 3 to 5 who were born full-term.

These research findings suggest a need to look at the marketing around formula, especially those terms like "sensitive," says Dr. Whaley. It makes sense to find out how often (and why) pediatricians are recommending lactose-reduced formulas, too.

The Link Between Lactose-Reduced Formula and Obesity

There are a few reasons why lactose-reduced formula may be associated with a higher risk for obesity. First, the glucose-based carbs used in them (including corn syrup) may negatively impact the gut microbiome, the trillions of bacteria found in the gut involved with many aspects of health, possibly including weight.

These infant formulas are also higher on the Glycemic Index (GI) than standard formulas. That's a measure of how much a food or drink impacts blood sugar. A higher GI formula may cause more rapid weight gain early on, a risk for obesity later in childhood.

The children in the study were all enrolled in the WIC program (the Special Supplemental Nutrition Program for Women, Infants, and Children), a federal nutrition assistance program that serves half of all children born in the United States.

All of the babies in the study lived in Southern California and most were Hispanic. More research is needed to see if the same results are found in other places and among other populations.

The USDA recently extended infant formula waivers to WIC families in order to be sure families have access to the food their babies need. The waivers were set to expire at the end of September 2022, but will now be available until December 31, 2022 or 60 days after the expiration of individual state's COVID-19 disaster announcement.

An Expert Weighs In

Bridget Young, Ph.D., an assistant professor of pediatrics at the University of Rochester, shares advice for caregivers who are shopping for formula:

Always talk to your pediatrician about what kind of formula is right for your baby. Avoid self-diagnosing your baby with lactose intolerance or lactose sensitivity or assuming that a "sensitive" formula will tame fussiness. If your baby is fussy, talk to your pediatrician about possible causes and ways to ease it.

Already using a lactose-reduced formula with success? "If your baby is thriving, you are doing a phenomenal job, so put this out of your mind," says Dr. Young. Some babies do need a lactose-reduced or lactose-free formula. "There's no room for any added stress or guilt," she says.

If you're starting from scratch and your baby is healthy with no underlying medical conditions, begin with a standard formula with lactose.

Keep in mind that terms like "sensitive" and "gentle" aren't regulated, and likely signal that the formula is lactose-reduced. Read the fine print and check the ingredient list for terms like "corn syrup solids."

Dr. Young also adds that obesity is incredibly complex and not the result of one formula choice—or even the decision to use formula.

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