Smithsonian.com

I’m not remotely Irish, but I always loved St. Patrick’s Day as a kid. My mother has a great sense of fun, especially when it comes to holidays. So on the morning of every March 17th, as my brother and I stumbled groggily downstairs for breakfast, we would be greeted with green: Green placemats; green napkins; green candles; a shiny green banner of letters strung across the dining room wall spelling out “Happy St. Patrick’s Day!”

Green food coloring in milk, courtesy Flickr user mr_orange

And best of all was our requisite daily glass of milk: On those mornings, the milk was miraculously green, with a giant marshmallow floating in it. The marshmallow was topped with a decorative plastic toothpick, shaped like a shamrock with a happy little leprechaun skipping across it.

I think this particular tradition was my mother’s unique invention (at least the marshmallow part), but I have other friends whose parents celebrated by cooking up green pancakes or “green eggs and ham,” Dr. Seuss-style, or baking batches of green-frosted cookies and cupcakes to share. And then there’s the green beer served up by many bars this time of year. It’s all made me wonder: What exactly is in green food coloring? Is it made from bugs, like red food coloring? Is it safe to consume in large quantities?

According to an article in Chemical and Engineering News, the color known as Green No. 3, or “Fast Green,” is a “petroleum-derived triphenylmethane.” Green food coloring can also be made by combining blue and yellow dyes, but either way, it’s usually synthetic. Chlorophyll would do the job naturally, but oddly enough, it’s not approved for use as a food coloring in the United States. (The FDA has only approved these nine color additives for use in food.)

The INCHEM database details the studies performed on rats, mice, hamsters and even beagles to test the safety of Green No. 3 as a food additive. It’s not exactly appetizing reading, I warn you—but basically, yes, it appears the chemical is safe to consume in small doses.

On the other hand, the Center for Science in the Public Interest recently included Green No. 3 on a list of artificial food dyes linked to behavior problems like ADHD in children. (Blue 1 dye, used in at least one popular brand of green food coloring, is also on the list of suspects.)

Judge for yourself, but personally, I’m concluding that a glass of green milk once a year is nothing to fear—and beyond that, I’ll stick to getting my greens in the form of vegetables.