Hari said she contacted the customer service departments of "every beer company under sun" for one year. Some released information on ingredients and others were not as responsive.
"They tell you the basic ingredients," she said, "but not the additives."
"However, an industry member who makes caloric or carbohydrate claims on a label must also include either a statement of average analysis, which provides the number of calories, as well as the number of grams of carbohydrates, protein and fat per serving size, or a serving facts statement, which adds the serving size and number of servings per container and may also include alcohol content," wrote TTB spokesman Thomas Hogue in an email to ABC News.
Allergen labeling is currently on a voluntary basis, although the TTB does require that additives like sulfite, which can cause life-threatening allergies, and yellow dye 5, which has been linked to hyperactivity in children, be on alcohol labels.
But alcohol makers must adhere to the "good manufacturing practices" enforced by the Food and Drug Administration and all its safety standards.
According to the FDA spokeswoman, Jennifer Dooren, substances directly added to food or that become part of food through contact must be safe, including ingredients used in "producing, manufacturing, packing, processing, preparing, treating, packaging, transporting or holding food."
Ingredients like high fructose corn syrup can be used "so long as their use is consistent" with the Code of Federal Regulations, or are generally recognized as safe, she said. The FDA maintains an inventory of "generally recognized as safe" or GRAS ingredients notifications on line.
Marino of MillerCoors wrote ABC News in an email, "If those regulations change, we certainly would be compliant."
"When we introduce a beer containing a non-traditional ingredient or utilizing a non-traditional brewing process, we must submit a formula to the TTB before receiving a Certificate of Label Approval (COLA)," wrote Marino. "That formula must contain a listing of all ingredients and the process that we will use in brewing our beers. Additionally, TTB may request a sample of our product and will periodically sample products in the marketplace to ensure the products comply with the approved formula and COLA. There is no TTB requirement to list the ingredients for beers on our labels since we are completely in compliance with all federal regulations controlling the brewing and labeling of our beers."
Marino added that MillerCoors was the first American alcohol company to participate in the TTB's new voluntary labeling guidelines as "step toward more transparency" with its brand Miller64.
"We are starting with Miller64 because, with its appeal to legal-drinking-age consumers who live an active, balanced lifestyle, we think the additional nutritional details will be especially relevant for Miller64 drinkers," he said. "This gives us an opportunity to get started down this path and learn more about consumer reaction."
An Anheuser-Busch spokesman told ABC News in an email that it "takes great pride in making our beers to the highest standards of quality and consistency, using pure, fresh, natural ingredients. For example, our flagship Budweiser and Bud Light brands are made with the best barley malt, rice, hops, yeast, and pure water."
The company said both those brands use American-grown rice, which by USDA standards does not contain genetically modified varieties. Anheuser-Busch cited its global consumer-information website for facts about ingredients and nutritional information.
"We, like all brewers large and small, brew all our beers to adhere to federal and state brewing and labeling standards," he said. "Our beer ingredients all meet TTB and FDA standards for food safety. ... Our beers must meet the high expectations of our consumers, which is why our high-quality ingredients and brewing standards are our top priority."
Hari said her initial research into beer ingredients stemmed from the 1982 book, "Chemicals Additives in Beer," by the Center for Science in the Public Interest. Now decades old, the book lists a number of ingredients that may or not be in beer today. But Michael Jacobson, the center's current director, said that what’s in beer is still “a big secret" and consumers deserve to know.
"Just because it sounds scary, doesn't mean the product is dangerous," he said. "It's my feeling that health problems or no health problems, consumers have a right to know the ingredients.”
Propylene glycol, which Hari pointed out is also in antifreeze, is a "harmless food additive," according to Jacobson. Even the permitted food dyes -- blue 1, red 40 and yellow 5 (which requires labeling) -- are rarely used in beer except to mix yellow and blue for green on St. Patrick's Day, he said.
"I presume there aren't many kids drinking artificially colored beer,” he said.
But caramel colorings that have been treated with ammonia in dark beers can be "a problem," he said, "though the caramel coloring industry has been cleaning up its act."
"[Hari] is generally in the right direction," he said. "She exaggerates, but who cares compared to the fact that these million-dollar companies refuse to disclose their ingredients and the government fails to require it.