Last week, a team of researchers from Dartmouth University released a widely publicized study with the somewhat provocative title “Arsenic, Organic Foods and Brown Rice Syrup.”
The study was yet another general reminder that words like “organic” or “natural” are not synonymous with the word “safe.” But more specifically it detailed unexpected amounts of poisonous arsenic compounds in everything from infant formula to snack bars, especially compounds containing rice or sweetened with brown organic rice syrup as a healthier alternative to high fructose corn syrup.
I’ll return to the question of exact amounts later; let us just note for now that all findings were in part per billions, numbers that may raise concerns about long-term exposure but do not suggest that anyone will be dropping dead after snacking on a cereal bar.
The more interesting immediate question anyway, at least to me, was: why were Dartmouth chemist Brian Jackson and his colleagues looking for arsenic in these supposedly healthy products at all? I rapidly discovered though that I just hadn’t been paying attention. They were simply following up on an issue well known in health science, a body of work establishing a troubling connection between rice and arsenic in the food supply.
In fact, my use of the word “unexpected” probably is more accurate in describing dismayed public reaction to the results. The authors of the new study emphasized that their working hypothesis, from the start, was that brown rice syrup would introduce arsenic into these foods.
So why rice in particular?
As it turns out, the rice plant is uniquely engineered to pick up arsenic from the environment. This begins with the fact that the plant is designed to easily absorb the mineral silicon which helps give rice grains their elegantly smooth structure. The crystalline structure of arsenic is just close enough that rice plants readily uptake arsenic as well. In fact, a toxic metal study, also from Dartmouth, described rice as “a natural arsenic accumulator.”
The efficiency of this system also means that the arsenic tends to be absorbed directly in its more toxic inorganic from rather than being converted to an organic form of arsenic. Here I mean organic not in the USDA-approved farming sense but in the chemistry sense in which organic refers to carbon-based compounds. And this is important because we metabolize organic arsenic compounds pretty neatly, reducing their toxic potential. It’s inorganic arsenic that’s most dangerous – it tends to bond tightly into living cells where it destroys them by disrupting their metabolism. And rice, experts say, may be the largest source of inorganic arsenic in our diets.
How does rice find the arsenic? Well, as I said, arsenic is a naturally occurring
element, sprinkled through soil and rock across the planet. I’ve put a basic arsenic map of the world here to the left to show you the general distribution and hotspots. This is geologic map, of course, and there can also be human introduction of arsenic into a region. A 2007 report, titled “U.S. Rice Serves Up Arsenic” noted that rice-growing regions in the Southeast appeared also show signs of contamination from early 20th century use of arsenic-based insecticides to control for pests like the cotton boll weevil. That study found higher levels of inorganic arsenic in Louisiana rice, for instance, than that from California’s Central Valley, which has a far greater natural distribution of arsenic.
But that map should also remind us that although rice seems to have an affinity for arsenic, we’re surrounded by and exposed to that poison on a daily basis in many different ways. A very thorough Consumer Reports write up of this latest research points out that last fall similar concerns were raised about arsenic contamination of fruit juices.
The Dartmouth study, in fact, did not turn up an arsenic free food product. The researchers looked at 29 brands of cereal bars, 22 contained a rice product and seven did not. All the cereal bars contained some trace of arsenic. Those without rice ranged from 7 to 28 parts per billion. As you might now expect, the readings from the rice products were higher, ranging from 23 ppb to a high reading of 128 ppb. Infant formula sweetened with rice syrup hovered close to 60 ppb.
And what does all that really mean? As the authors note, the U.S. Food and Drug Administration (FDA) does not set a safe arsenic standard for food. (And we’re not along in that. A Canadian Broadcasting Corporation story on the Dartmouth findings also noted a lack of public health standards for arsenic food exposure in that country.) But the U.S. Environmental Protection Agency (EPA) has established a 10 part-per-billion level for drinking water.
In an interview with NPR, Jackson said the EPA standard should probably be considered in assessing risk for something like infant formula – also a liquid consumed on a daily basis. It works less well for cereal bars and occasional consumption only and by a generally much larger, less vulnerable human being. And it’s almost important to note than the 10 ppb standard signifies EPA’s effort to set standards far, far below an actual toxic effect.
In other words, these are pay attention numbers rather than immediate alarm numbers. They should remind us that, as always, a varied diet is healthier than relying too much on any single source of food. But as Jackson also pointed out the growing body of work on arsenic contamination of food in general, should also serve as prompt to our government agencies to take some of these unexpected hazard issues out of our food supply, start working out those much needed official safety standards for arsenic in our diet, and provide us with some kind of realistic assessment that will allows to make our own decisions about such risks.
I couldn’t agree more.