Originally Published: 11 AUG 22 07:33 ET

Updated: 11 AUG 22 10:49 ET

By Sandee LaMotte, CNN

(CNN) -- Making baby food at home with store-bought produce isn't going to reduce the amount of toxic heavy metals in the food your baby eats, according to a new report released exclusively to CNN.

"We found no evidence to suggest that homemade baby foods made from store-bought produce are better than store-bought baby foods when it comes to heavy metal contamination," said the paper's coauthor Jane Houlihan, research director for Healthy Babies, Bright Futures. An alliance of nonprofits, scientists and donors, HBBF, which produced the report, has a stated mission of reducing babies' exposures to neurotoxic chemicals.

Researchers tested 288 foods bought at stores and farmers markets across the United States -- including grains, fruits, vegetables, snacks, teething foods, and family items that babies eat, such as cereals and rice cakes -- for lead, arsenic, mercury and cadmium. Those heavy metals are among the World Health Organization's top 10 chemicals of concern for infants and children.

"Toxic metal exposure can be harmful to the developing brain. It's been linked with problems with learning, cognition, and behavior," according to the American Academy of Pediatrics.

Researchers also pored over data from 7,000 additional food tests reported in published studies and by the US Food and Drug Administration.

Results showed 94% of manufactured baby foods, family foods and homemade purees made from purchased raw foods contained detectable amounts of one or more heavy metals.

Lead was found in 90% of manufactured baby food bought by shoppers for the report and 80% of store-bought family food and homemade purees. There is no safe level of lead, according to the AAP.

Arsenic was found in 68% store-bought baby food and 72% of family food either purchased or prepared at home. Cadmium was found in 65% of purchased baby food and 60% of family foods, and mercury was in 7% of store-bought baby food and 10% of family foods. (The highest levels of mercury are found in seafood, which was not tested in this analysis.)

READ MORE: 95% of tested baby foods in the US contain toxic metals, report says

The new report is a follow-up to a November 2019 report in which Healthy Babies, Bright Futures tested 168 foods purchased from major baby food manufacturers. That analysis found 95% of store-bought baby food contained lead, 73% contained arsenic, 75% contained cadmium and 32% contained mercury. One-fourth of the foods tested that year contained all four heavy metals.

"After that report we saw so many people saying you can get around this problem by making your own baby food at home, so we decided to check," Houlihan said. "We suspected we'd find heavy metals in all kinds of food because they're ubiquitous contaminants in the environment.

"And that is exactly what we found -- heavy metals were in foods from every section of the store," Houlihan said. "What this says is that as the FDA is setting standards for heavy metals in baby food, they need to go beyond the baby food aisle."

What's a parent or caregiver to do? Feed baby with as many different types of foods as possible, said pediatrician Dr. Mark Corkins, chair of the Committee on Nutrition of the American Academy of Pediatrics. He was not involved in the study.

"If you spread foods out, and offer a wide variety of options, you'll have less toxicity," Corkins said. "And nutritionally that's always been the right thing to do to get the most micronutrients from the food you eat."

Does buying organic help?

The report found buying organic didn't lower heavy metal levels either, which was "not shocking or surprising," said Corkins, a professor of pediatrics at the University of Tennessee Health Science Center and Le Bonheur Children's Hospital in Memphis, Tennessee.

"It's the soil and water that's contaminated with arsenic and other heavy metals, so it doesn't matter if it's organic or traditional farming methods," Corkins said. That would apply to locally grown crops or even backyard gardens, if the soil had not been verified to be metal-free.

However, buying organic can help avoid other toxins the new report did not consider, such as herbicides and pesticides, said Dr. Leonardo Trasande, director of environmental pediatrics at NYU Langone Health. He was not involved in the study.

"There are other benefits to eating organic food, including a reduction in synthetic pesticides that are known to be as bad for babies, if not even more problematic," Trasande said.

"We've seen multiple studies show significant effects of synthetic pesticides on cognitive function in children as a result of prenatal exposure. We've seen images of the brain where certain parts are smaller that are crucial for higher order functioning after exposure," he added. "A simple step would simply be to say eat organic because regardless of anything we're talking about in this report, it's good for you."

Experts agree that battling toxins in baby foods is a job for government organizations who will need to work with growers, suppliers and manufacturers to institute regulations and safeguards. In the meantime, parents can make a difference.

"Making even one simple choice every day to lower a child's exposure will make a difference, whether that's staying away from rice-based snacks and serving a diced apple instead or choosing not to serve carrots and sweet potatoes every day," Houlihan said.

"With heavy metals and other toxins the risks add up over a lifetime," she added. "So even if some of these foods had been served to a child up to their second birthday, starting from there to lower exposure to toxins is going to add up. Every choice matters."

Least contaminated foods

Tested foods with low metal content contain one-eighth as much heavy metal contamination as foods with the highest levels, Houlihan said. These are foods that can be "eaten freely," the report suggested.

Fresh bananas, with heavy metal levels of 1.8 parts per billion, were the least contaminated of foods tested for the report. That's an "82-fold difference in average level of total heavy metals" from the most contaminated food, rice cakes, which tested at 147 parts per billion, according to the investigation.

After bananas, the least contaminated foods were grits, manufactured baby food meats, butternut squash, lamb, apples, pork, eggs, oranges and watermelon, in that order. Other foods with lower levels of contamination included green beans, peas, cucumbers, and soft or pureed home-cooked meats, the report found.

Infant formula made with lead-free tap water was recommended. Tap water that has been tested and is free of lead is always a good choice. Milk is also a good choice, but only for babies 12 months and older.

Some healthy lower-metal foods, such as yogurt, unsweetened applesauce, beans, cheese, hard-boiled eggs and grapes that have been cut lengthwise, were good choices for snacks for babies, according to the report.

Fresh and frozen fruit -- including those used in homemade purees -- were options as well. But don't use canned fruits if you can avoid it: "Tests find lead 30 times more often in canned fruit than in fresh and frozen fruit," the report stated.

Parents and caregivers can also lower their baby's exposure to heavy metals by making some smart substitutions, the report said.

Using a frozen banana for a teething baby instead of a rice-based teething biscuit or rice rusk could lower total intake of heavy metals by 95%, according to the report. Another suggested teething aid: peeled and chilled cucumber spears.

Avoid or limit these foods

The most heavily contaminated foods eaten by babies were all rice-based: "Rice cakes, rice puffs, crisped rice cereals and brown rice with no cooking water removed are heavily contaminated with inorganic arsenic, which is the more toxic form of arsenic," Houlihan said.

Arsenic is a natural element found in soil, water and air, and because rice is grown in water, it is especially good at absorbing inorganic arsenic. ("Inorganic" is a chemical term and has nothing to do with the method of farming.) Brown and wild rice are the worst offenders, as the bran contains the highest arsenic concentrations.

READ MORE: New FDA limits on arsenic levels in infant rice cereals don't adequately protect children, critics say

Prior research has shown that even low levels of inorganic arsenic exposure can impact a baby's neurodevelopment. A meta-analysis of studies on the topic found 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.

Testing by HBBF found rice cakes were the most contaminated with inorganic arsenic, followed by crisped rice cereal, rice-based puffs and brown rice. The report recommended those foods be avoided entirely, unless the brown rice is cooked with extra water that is poured off before consumption (much like pasta). It's best to do that with all rice, including white and wild rice, the report said, as it can reduce arsenic levels by up to 60%.

Rice-based teething biscuits or rusks and white rice came next on the most contaminated list, the report said. White rice is milled to remove the outer layers, but experts say arsenic levels remain high enough to be concerning, especially if rice is a daily staple.

"Inorganic arsenic averaged 100 parts per billion in brown rice infant cereal and 74 parts per billion in white rice infant cereal in our tests," Houlihan said. "Baby food companies have taken brown rice cereal off the market because of its high arsenic levels."

Parents and caregivers can help by staying away from high-arsenic varieties of white rice grown in Arkansas, Louisiana, Texas, or simply "US" and instead choosing lower-arsenic basmati rice from California, India and Pakistan, as well as sushi rice from the US, the report said.

Serve these foods rarely

After rice-based foods, the analysis found the highest levels of heavy metals in raisins, non-rice teething crackers, granola bars with raisins and oat-ring cereals. But those were not the only foods of concern: Dried fruit, grape juice, arrowroot teething crackers and sunflower seed butter all contained high amounts of at least one toxic metal, according to the report.

"Many foods have a kind of unique, heavy metal profile," Houlihan explained. "For example, we saw very high levels of cadmium in things like spinach, leaf lettuce and peanut butter."

However, the human body doesn't absorb cadmium as easily as other heavy metals, and for that reason "it doesn't have as high a level of concern," Houlihan added.

"There's also not as much evidence that cadmium is neurotoxic to babies, or at least the body of evidence isn't there at the same levels as lead and arsenic," she said. "Lead and arsenic damage isn't reversible -- these are permanent impacts on IQ, learning ability and behavior, so it's a big deal."

Root and tuber vegetables may have higher levels of heavy metals like lead and arsenic because they grow underground. In fact, the investigation found that nutritious baby favorites like carrots, sweet potatoes, squash and many types of potatoes did have concerning levels of heavy metals.

Even the same food could have varying levels of toxic metals, according to the report. For example, a shopper in Raleigh, North Carolina, bought a sweet potato with 60.7 parts per billion of lead -- 10 times more than the store-bought sweet potato puree she purchased. A Chicago shopper purchased a fresh carrot with eight times more arsenic than the premade carrot baby food she took home, the investigation found.

Yet shoppers in Tennessee and California found the opposite -- their fresh produce had minimal levels of heavy metals compared with the manufactured baby food brands they bought.

"As a parent, you don't know what you're picking up out of the produce bin," Houlihan said. "Is it elevated because of the cultivar -- the particular type of sweet potato or carrot? Or is it elevated because it's grown in an area where the soil has naturally high levels of lead?

Answering these questions will be the responsibility of government regulators and industry, Houlihan said. The FDA has a Closer to Zero campaign, for example, which could take on the issue.

CNN has reached out to the FDA for comment but hasn't yet received a response.

"And remember, if you're protecting the basic ingredients that parents are using to make food at home, you're not only protecting babies and toddlers, you're protecting pregnant women as well. Babies in utero are particularly vulnerable to toxins while the brain is growing at such a rapid pace."

With no way of knowing levels of toxic metals in the soil where produce is grown, parents and caregivers need to add one more step to their efforts to avoid these substances, Houlihan suggested. In addition to mixing up the variety of foods and not serving the same options each day, parents can "choose different brands or varieties of foods or shop in different stores from week to week to avoid choosing a high-metal source regularly."