Feeding babies cereal, bread and crackers, which are high in sodium, may trigger a yearning for salt that lasts a lifetime, according to a new study that examined when and why people start hankering for the taste of salt.
The research is important because health authorities around the globe have been calling for people to reduce their sodium intake, which has increased over the last 50 years. But despite the public-health pronouncements, persuading people to shun salt hasn’t been successful. “We are built to like salt,” says Leslie Stein, a senior research associate at Monell Chemical Sciences Center, a nonprofit research institute in Philadelphia that studies the mechanisms and functions of taste and smell.
In fact, humans need salt to survive — just not as much as we’re eating. The average American consumes 3,436 mg of sodium a day, more than double the government’s recommended daily maximum. Sodium helps maintain blood pressure, send nerve messages and plays a role in muscle contraction. But too much has been linked to high blood pressure, a risk factor for heart disease and stroke.
Most of the salt we consume is in processed foods — bread has lots of salt, as do cereal and cakes, cheese and meat, and, of course, snack foods. Researchers know people like salt, but they don’t know why. Scientists understand the mechanism of sweet and bitter taste receptors, but they don’t have a good grasp of how salt taste receptors work. And while babies come out of the womb with a built-in preference for sweet and a strong aversion to bitter, it appears that they are indifferent to salty for the first few months of life.
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To try to puzzle it out, Monell researchers studied 61 infants from the Philadelphia area at 2 months, then again at 6 months of age. At both points, they gave the babies three bottles, each containing water; a 1% salt solution, which mimics the saltiness of chicken noodle soup; or a 2% salt solution, which is the equivalent of doubling that bowl of chicken noodle soup’s saltiness.
The babies were given two minutes to drink out of each bottle. To assess each infant’s affinity for salt, researchers compared how much salt solution they drank compared to plain water. If they drank more of the salty bottles, they were categorized as preferring the salt solution; if they drank less, they were classified as rejecting it. Babies who drank the same amount of water or salty liquid were described as indifferent.
At 2 months of age, researchers found that babies were indifferent to the 1% solution and flat-out rejected the 2% mixture. But by 6 months, some appeared to have developed a taste for salt. Babies who had already begun eating starchy, sodium-packed morsels like Cheerios and bread in the interim showed a preference for both salty solutions, while babies who had stuck to baby food and low-salt foods like fruits and vegetables did not, according to the research, which was published this week in the American Journal of Clinical Nutrition. “Dietary experience can influence babies’ preference for salty taste,” says Stein, the study’s lead author.
The results don’t prove that early introduction of starchy table foods causes a later preference for salt; they show only an association between the two. But, if they hold up, the findings suggest that parents may have an easy way to reduce kids’ risk of becoming salt fiends later on.
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To back up their findings in the infants, Stein circled back with 26 babies once they became preschoolers. Within that group, 12 had been introduced to starchy table foods before they were 6 months old, and 14 had not.
Mothers were asked about “salt-directed behaviors”: did their kids put salt on unusual foods like oranges? Were they likely to lick salt off foods such as pretzels before eating them? Moms with children who’d started on starchy foods before they were 6 months old were more likely than the other group to report that their kids liked to consume plain salt by licking it off, for example.
The small study is far from the last word on children’s sodium intake. But it does offer some food for thought: perhaps the public-health campaign to reduce salt intake may need to start in childhood and even infancy. “It might be a guide for parents about how to introduce their children to healthy foods,” says Stein.
Bonnie Rochman is a reporter at TIME. Find her on Twitter at @brochman. You can also continue the discussion on TIME‘s Facebook page and on Twitter at @TIME.