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Put a bunch of 4-year-olds in a room and place two childhood favorites in front of them: salted pretzels and M&Ms. Then tell them to help themselves - what they choose may have a lot to do with their weight when they were born.
It also may shed light on the risk factors for hypertension later in life.
Curious about links between low birth weight and future risks for heart disease, and between salt and hypertension, researchers began a study to see whether some children are born liking salt more than other children. They tested about 80 children at 2 months, at 6 months, and at 3 to 4 years.
"Given that we know that there's a large literature that suggests that the intake of sodium is related to the risk of hypertension, we wanted to see if there was any link between birth weight and a liking for salt," says Leslie Stein, a researcher with the Monell Chemical Senses Center, an institute in Philadelphia focused on understanding smell, taste and chemical irritation.
By 2 months, smaller babies, or those 5.5 pounds at birth, liked salt more than their peers born at 8 or 9 pounds. They drank salted water that bigger babies rejected. By age 3 to 4, the children born smaller were choosing pretzels and potato chips while children born larger were picking chocolates and unsalted banana chips, according to Stein's research, published Nov. 23 in an advance online issue of the European Journal of Clinical Nutrition.
"It's a first step in showing there could be a link between birth weight and hypertension later in life," she says.
To understand what health effect, if any, a preference for salty foods might have when the smaller babies grow to be adults means entering science's unresolved salt wars.
Some experts, including those at the National Heart, Lung and Blood Institute, believe that Americans should reduce salt intake. The American Heart Association and the Institute of Medicine recommend no more than a teaspoon each day to reduce the risk of high blood pressure and heart disease - a dose exceeded by 95 percent of American men and 75% of women.
Other experts believe that salt has little bearing on heart disease, and even a drastic reduction in salt does little to bring down high blood pressure. After at least 30 years of medical studies, the question remains unresolved.
What science does know, says Dr. Curtis Morris, professor at the University of California, San Francisco, and member of the Institute of Medicine's panel on Dietary Reference Intakes which made recommendations in 2004 for nutrients including sodium and potassium, is that some people are salt sensitive.
"It turns out that there are people whose blood pressure goes up when they ingest a salt load and goes down when salt is diminished," says Morris. "It's directly related to the dietary salt." There's no way of knowing who those people are until they show up in a doctor's office with hypertension and are tested with high- or low-salt diets.
Further confusing the issue is that some people with normal blood pressure of 120/80 can have the same spike in blood pressure when they eat a lot of salt. Those people, says Morris, are at high risk for future hypertension.
Perhaps the biggest problem with salt restriction is that salt is everywhere - in processed foods, fast foods, breads, soups - not just the shaker.
Another dietary tactic, says Morris, is to increase potassium in the diet by eating six or more servings of fruits and vegetables. That has been shown to lower blood pressure, even in salt-sensitive people.
But many Americans eat only half that amount of fruits and vegetables. Upping the potassium could be as hard as lowering salt for Americans who grow up loving either pretzels or M&Ms.