(CNN) Ask any mom or dad to name their baby's first food. The likely answer? Rice cereal. What's a common go-to "healthy" snack for toddlers and kiddos? Rice cakes.

Yet a growing amount of scientific evidence is pointing to an alarming connection between inorganic arsenic in brown and white rice and harm to children's immune systems and intellectual development.

Concentrations of arsenic were twice as high in the urine of infants who ate white or brown rice than those who ate no rice, according to research published Monday in JAMA Pediatrics . Arsenic levels were highest in babies who ate rice cereal, often given several times a day to introduce babies to solids.

In April, the FDA proposed a limit of 100 parts per billion of inorganic arsenic in infant rice cereal. That proposal is still in the public comment phase . The European Food Safety Authority has already moved to limit inorganic arsenic in rice products to that level.

"Arsenic is a known carcinogen that can influence risk of cardiovascular, immune and other diseases," said Margaret Karagas , an epidemiologist who studies the effects of toxic metals at Dartmouth College, and the lead researcher on the new study. "There's a growing body of evidence that even relatively low levels of exposure can have an adverse impact on young children."

Prior research has shown that even low levels of arsenic exposure can impact a baby's neurodevelopment. A 2004 study looked at children in Bangladesh who were exposed to arsenic in drinking water, and it found that they scored significantly lower on intellectual tests. A meta-analysis of studies on the topic found that a 50% increase in arsenic levels in urine would be associated with a 0.4-point decrease in the IQ of children between the ages of 5 and 15.

Other studies have looked at how inorganic arsenic exposure in utero could alter a baby's immune system. A 2013 study of levels of arsenic in pregnant women who ate rice products found that even low levels of exposure to inorganic arsenic in utero were related to infant respiratory infections in the first four months of life. Babies exposed to the highest levels were associated with severe infections that needed antibiotics to resolve.

Why rice?

Arsenic is a natural element found in soil, water and air, with the inorganic form being the most toxic. ("Inorganic" is a chemical term and has nothing to do with the method of farming.) Because rice is grown in water, it is especially good at absorbing inorganic arsenic and, according to the Food and Drug Administration, has the highest concentration of any food

Rice plants absorb high levels of arsenic from the water and soil.

If you think it's only imported rice, think twice. "U.S.-grown rice has some of the highest reported arsenic concentrations in the world," Karagas said.

And in this case, brown and wild rice are the worst offenders , because the milling process used to create white rice removes the outer layers, where much of the arsenic concentrates.

But moving your family to white rice might not be enough protection. In a prior study , Karagas and her associates found that brown rice syrup, a frequent sweetener in organic foods, was also a source of significant levels of arsenic. One "organic" milk formula marketed to toddlers had levels of inorganic arsenic that were six times the levels currently considered safe by the U.S. Environmental Protection Agency.

What's a parent to do?

Pediatrician Tanya Altmann , author of "What to Feed Your Baby: A Pediatrician's Guide to the 11 Essential Foods to Guarantee Veggie-Loving, No-Fuss, Healthy-Eating Kids," said she's changed her guidance on first foods. She recommends "tossing white rice cereal, as there is little nutritional benefit and it simply primes young palates for a lifetime of eating white carbs, not to mention the arsenic issue, which this study confirms."

She echoes the advice of the American Academy of Pediatrics , which advises parents to offer a wide variety of foods including grains such as oats, barley, wheat and quinoa.

"Best first foods for infants are avocado, pureed veggies, peanut-butter oatmeal and salmon," Altmann said. "They all provide important nutrients that babies need, help develop their taste buds to prefer healthy food and may decrease food allergies."

She believes meats are a better source of iron and zinc for babies than rice cereal, "so I haven't been recommending rice cereal as a first food for several years."

And if parents insist on rice cereal, Altmann said, "I always recommend brown rice over white rice. I personally prefer whole-grain oatmeal mixed with peanut butter to decrease risk of peanut allergies later in life, and quinoa cereal mixed with vegetables."

What about snack foods?

Join the conversation See the latest news and share your comments with CNN Health on Facebook and Twitter.

"There's no reason that snack food has to be packaged and processed," Altmann said. "I recommend parents offer real, single-ingredient foods as much as possible for both meals and snacks."

Altmann recommends "berries, steamed or cooked veggies, peanut puffs, Greek yogurt, string cheese, a thin layer of nut butter on whole-grain bread, hard-boiled or scrambled egg, whole-grain O-shaped cereal and pieces of lean chicken (or whatever is left over from lunch or dinner)."