How to Make the Perfect Green Beer, According to Science

Not even St. Patrick wanted green intestines.

Leyla A./Flickr

It’s safe to say that the American tradition of St. Patrick’s Day has deviated from the traditional Irish observation of the feast. While the holiday still tips its hat to shamrocks, gingers, and all things Irish, the most American icon of St. Patrick’s Day is green beer.

It’s arguable whether the beverage looks appetizing, but to ensure that the beer doesn’t destroy human intestines, we looked to science to find the best recipe for a happy St. Patrick’s Day.

Who Made the First Green Beer?

The tradition of green beer, which is now a hallmark of the holiday worldwide, began in the United States. The original recipe is credited to Professor Thomas H. Curtin, a New York physician, who gave the brew a green hue by using an iron-based laundry whitener referred to as “wash blue.” (This is a limerick waiting to happen.)

While modern green beer no longer includes laundry whitener, the most common ingredients can still harm the GI tract. Of the 4.2 billion pints of green beer that are consumed during the holiday, most of that lush green color is derived from a synthetic organic compound called Fast Green FCF. (It’s also known as Food Green 3, Solid Green FCF, and C.I. 42053 if you’re checking labels.)

While the FDA has approved this food dye, which is mostly used to make canned veggies look greener, it’s banned across the European Union.

Ball-and-stick model of Fast Green FCF molecule. The structure is taken from ChemSpider.

That’s right, the kind of green beer most bars are serving in the United States is prohibited in Ireland.

Fast Green has far worse qualities than being inauthentically Irish, though. The substance has been found to have tumorigenic and mutagenic effects in studies on animals and humans. It also does a number on human intestines.

For those trying to avoid green intestines this holiday season, researchers have found safer and better-tasting alternatives in spirulina, matcha, and wheatgrass.


Wikimedia Commons

The first step in creating the perfect green beer is selecting the right beer base. Guinness and other stouts are difficult to dye, so it’s easiest to begin with a pilsner or blonde ale. Hefeweizens could also work, but their often cloudy consistency will dull the green hue.

How to Make Green Beer in Three Steps

1. Once the beer is selected, decide the shade of green desired. For a bright, yellowy green, closest to resembling a beer using Fast Green, throw wheatgrass into a juicer and float a few ounces of it on top of the beer. This will have the opposite effect of typical food dyes, as wheatgrass is often used to help with digestive issues, most notably reducing the impact of ulcerative colitis.

2. However, adding a juice means adding a flavor to the beer. If the taste of wheatgrass isn’t your thing, add matcha powder instead.

3. Using a small whisk, stir in 1 teaspoon of matcha powder until fully dissolved. The powder gets is color from chlorophyll and will give the beer a duller, olive-green color, but since it’s sourced from green tea, it will also add an extra boost of energy. Think of this as an organic Red Bull/vodka.

While matcha and wheatgrass are becoming popular alternatives in the beer dying tradition, the ingredient most endorsed by researchers is spirulina. Not only is the blue-green algae rich in vitamins to help with that inevitable hangover, but its increasing demand on St. Patrick’s Day has led to larger mass production from scientists.

Dr. Chris O'Malley with the St Patrick's Day pint.

Newcastle University

Stu Brew, a student-run sustainable microbrewery from Newcastle University in the UK, has created a St. Patrick’s Day green pint by mixing the blue phycocyanin from spirulina with a pale ale. The university is working with Scottish Bioenergy to mass produce the blue pigmented spirulina on an industrial scale to meet the rising demand.

“Demand for phycocyanin has increased massively because people want natural, not artificial food colorants,” Dr. Chelsea Brain of Newcastle University told the press. “But at the moment, it’s still very expensive to produce.”

Brain’s team was able to bypass this problem by exposing the algae to long wavelength red light. “We found that we could produce over five times the amount of ‘blue’ using long wavelength red light, reducing the cost of production and also improving efficiency.”

Spirulina will turn beer into a frothy, dark green drink.


The process is already catching on in the United States. Dogfish Head sells “Verdi Verdi Good,” a beer dyed with spirulina, while Freetail Brewing Company offers a Belgian-style “Spirulina Wit.”

To make this green brew at home, pick up spirulina powder from a local grocery store and add a pinch to your pint. A little goes a long way to create a dark green pigmentation, and thanks to spirulina’s protein content, the beer’s head might have a thicker foam than usual.

The delicacy of green beer has come a long way since its laundry whitener days in the 20th century, and thanks to scientific research meeting consumer demands, the quality of its ingredients continues to improve. This could finally be the St. Patrick’s Day where your intestines aren’t the color of a shamrock.

Related Tags