Giving a baby their first bite of real food – it’s an indelible memory. That breathless moment as you wait to see whether it will be swallowed or unceremoniously rejected, the look of astonishment on their little face. For many of us, that first bite was rice cereal – gentle on the stomach, easy to mix with breast milk or formula, safe, trusted, traditional. Well it turns out we’ve been poisoning our children all along.  Well, at least that’s what a paper appearing in JAMA Pediatrics would have you believe.

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The relevant background here is that arsenic, in sufficient quantities, kills you. And rice, in part because it is often grown in flooded paddys, concentrates arsenic. And between rice cereal, rice-based formula, and those little puffy rice treats, infants eat a fair amount of rice.

In this study, researchers from Dartmouth examined 759 infants enrolled in the New Hampshire Birth Cohort study. Rice consumption was pretty common – when surveyed at 12 months of age, the majority of babies had consumed some rice product within the past 2 days.

In a subgroup of 129 infants, the researchers examined total urinary arsenic levels and correlated them with food diaries taken at several points over their first year of life. Sure enough, the kids who had eaten more rice products had higher levels of urinary arsenic. Kids who had no rice consumption had an average urinary arsenic concentration of around 3 parts per billion, compared to around 6 parts per billion among those who had been eating white or brown rice. Breaking it down farther, the highest arsenic levels were seen in kids eating baby rice cereal – around 9 parts per billion.

But… does it matter? The CDC lists arsenic as a known carcinogen, but it is often hard to find precise toxic dose numbers.  Here’s what I’ve dug up.  It looks like the lethal dose is around 2mg/kg. To get that dose, a 5 kilogram infant would need to ingest, in a short period of time, roughly 50 kilograms of strawberry flavored puffed-grain snacks.  That was the food with the highest arsenic levels in this study.

But chronic, sub-lethal exposure to arsenic may also be harmful. As I mentioned above, arsenic is a known carcinogen. There is also some mixed data that suggests that high arsenic exposure can lead to lower intelligence scores in children, though the levels measured in those studies are about ten times what we see here.

The bottom line is, we don’t know if this is a big problem. My impression is that arsenic contamination of drinking water is more problematic than the arsenic content of foods.  So yeah, avoiding rice-containing products may get the arsenic levels in infants from very low to very very very low, but what shall we give them instead? Arsenic is just one potential toxin in one group of foods. In this modern world, you may have to pick your poison.