Food blogger Vani Hari's husband's favorite drink is beer and, just in time for his birthday this week, she is launching an online petition to ask the two biggest producers of American beer to list all their ingredients and brewing methods.
Hari claims some beers contain additives like high-fructose corn syrup, stabilizers and artificial flavoring, which have been linked to obesity, allergies, hyperactivity and gastrointestinal problems. She also alleges that big brewers use unappetizing things like propylene glycol – a foaming ingredient found in airplane deicing liquid – and even use fish swim bladders during brewing for clarity.
"That was alarming to me," Hari, 35, of North Carolina, told ABC News. "I thought beer was just hops, water, yeast, malt and barley."
The fact is no one but the manufacturer – not even Hari – knows for sure what's in beer or what’s used to make it, because the federal government does not require companies to disclose their ingredients or brewing processes. Hari is on a mission to get more transparency in the beer industry.
Her point is that consumers just don't know how their food and drink is made or what they put into their bodies.
"I just want full disclosure," she said, "not to change labels and go through government labels -- just to disclose it online so everyone can see."
Both MillerCoors and Anheuser-Busch told ABC News that they were in full compliance with all federal and state labeling requirements.
An Anheuser-Busch spokesman told ABC News that it uses none of the ingredients cited by Hari in its "flagship brands," Budweiser and Bud Light.
Peter Marino, a spokesman for MillerCoors, told ABC News that its ingredients are "proprietary information."
"That being said, we are happy to provide allergen information, which, in our case, involves wheat," Marino said. "We do not use nuts or dairy in the brewing process. And we don't use fish bladders either."
But Hari argues that proprietary recipes shouldn’t trump transparency.
"Coca Cola has kept their secret formula under lock and key for years," she said. "However, Coca Cola also releases the full set of ingredients on their labels -- something beer manufacturers have kept hidden for years and our government has neglected to mandate."
The average American drinks about 21 gallons of beer annually, making it the third-most-popular drink in the United States, after soda and bottled water, according to a 2010 article in Advertising Age. Beer is still the most popular alcoholic beverage, a favorite among 36 percent of Americans, according to a 2013 Gallup Poll.
"In this new decade of information about food and what we are consuming, we don't know what is in the world's most popular drink," said Hari.
Hari, an activist known as the Food Babe, takes credit for two other consumer victories: getting Kraft to remove yellow dyes from its children's Mac & Cheese products; and urging Subway to get an ingredient used in yoga mats out of its bread.
"My husband loves beer and it's one of the things that he brings into the house, and I didn't know what was in it," Hari told ABC News. ""I am very meticulous about ingredients that I put in my family's bodies. So I started to investigate."
Hari claims that MillerCoors has admitted to using high-fructose corn syrup in several of their brands, and said some of their products may contain genetically modified corn because of its prevalence in the U.S., but the companies would not comment on these claims to ABC News.
She also noted that some other brewers darken their beers with caramel color, a compound that is under review by the FDA for potential health hazards.
Neither MillerCoors nor Anheuser-Busch would comment to ABC News on whether their products contain caramel coloring.
As for fish bladders, some beer and wine manufacturers extract and dry them to use as filters, to help rid the beverage of particles.
The powder, known as isinglass, has historically had wound-healing properties, according to an April article in Newsweek. But, as the article noted, it renders those beverages "drinkable but also unsuitable for vegetarians."
"Just like dairy manufacturers pump cows with antibiotics and growth hormones, the beer companies should be up front about their processing and disclose that they are using fish bladders," said Hari.
She also alleged that some beer makers use "chemically altered hop extract," known as tetrahops, to add a bitter flavor and give it a longer shelf life.