Beer contains four core ingredients: malted grain (usually barley), water, hops, and yeast. But the finished product is far more complex than that short list suggests. Fermentation transforms those raw materials into a drink carrying alcohol, carbohydrates, B vitamins, minerals, antioxidant compounds, and dozens of flavor-active molecules. Here’s what’s actually in your glass.
The Four Base Ingredients
Water makes up roughly 90 to 95 percent of any beer, and its mineral profile affects the final taste. Malted barley is the primary grain in most styles. During malting, enzymes inside the grain activate and convert stored starch into fermentable sugars. Those same enzymes break down proteins into nitrogen compounds that feed the yeast during fermentation.
Hops contribute bitterness, aroma, and natural preservative properties. The specific variety and the point at which they’re added during brewing determine whether a beer leans more bitter or more aromatic. Yeast does the heavy lifting of fermentation, consuming the sugars from the malt and producing ethanol (alcohol) and carbon dioxide. Yeast also generates a wide array of aroma and flavor compounds that shape a beer’s character, which is why the same grain and hops can taste completely different depending on the yeast strain.
Calories, Carbs, and Protein
A standard 12-ounce can of regular beer contains about 153 calories, 12.6 grams of carbohydrates, and 1.6 grams of protein. Nearly all of those carbohydrates come from residual sugars and dextrins that the yeast didn’t fully ferment. Light beers bring both numbers down by fermenting more of the available sugar, which simultaneously reduces carbs and alcohol calories. Heavier styles like double IPAs or imperial stouts push calorie counts well above 200 per serving.
Alcohol Content Across Styles
The alcohol in beer is ethanol, produced during fermentation. How much ends up in your glass varies dramatically by style. Light lagers average around 4.0% ABV. A standard American adjunct lager sits near 5.0%, and a Czech pilsner lands right at 5.0% as well. Pale ales and amber ales cluster in the 5.4 to 6.0% range. From there, stronger styles climb quickly: Belgian tripels and imperial stouts routinely reach 8 to 12% ABV. At the other end, non-alcoholic beers contain between 0.0% and 0.5% ABV, achieved either by removing alcohol after fermentation or by limiting fermentation in the first place.
B Vitamins and Minerals
Beer is not a multivitamin, but it does carry measurable amounts of several B vitamins and minerals, all derived from the original grain. Niacin (B3) is the most abundant B vitamin per serving. Riboflavin (B2), pantothenic acid (B5), and B6 are present in smaller quantities. The standout is folate: a single 330 mL can of beer provides roughly 20 to 25 micrograms, covering 10 to 15 percent of the recommended daily intake for men and 5 to 7 percent for women.
On the mineral side, potassium and phosphorus are the most plentiful, followed by magnesium, calcium, and sodium. Beer also contains silicon, a trace mineral linked to bone health. Studies measuring 76 beers from across the UK, Europe, and Asia found an average silicon content of about 19 ppm, with individual beers ranging from 9 to 40 ppm. No consistent pattern tied silicon levels to a particular beer style or country of origin.
Polyphenols and Antioxidants
Both hops and barley contribute polyphenols, plant-based compounds with antioxidant activity. The two most abundant polyphenols in finished beer are gallic acid and ferulic acid. A more unusual compound is xanthohumol, a flavonoid that comes exclusively from hops. Beer is the only dietary source of xanthohumol in the human diet, though the amount is small: typical beers contain around 0.1 mg per liter. Dark beers tend to have higher concentrations because compounds formed during the browning of malt help protect xanthohumol from breaking down during brewing. Experimental dry-hopped dark beers have reached levels of 1.8 to 3.8 mg per liter, but those are not standard commercial products. Xanthohumol’s ability to neutralize free radicals is comparable to the catechins in green tea and several times stronger than vitamins C and E.
Flavor Compounds From Fermentation
Yeast doesn’t just produce alcohol and CO2. It generates dozens of volatile compounds that define how a beer smells and tastes. At least 20 of these are considered important in a standard pilsner alone. They fall into a few key categories.
Esters are responsible for fruity and floral notes. Isoamyl acetate gives off a banana-like aroma and is one of the signature flavors in German wheat beers. Ethyl acetate contributes a lighter, solvent-like fruitiness at low levels. Ethyl hexanoate and ethyl octanoate add hints of apple and tropical fruit.
Higher alcohols, sometimes called fusel alcohols, create heavier, warming sensations. Isoamyl alcohol is the most prominent, and when its concentration rises, tasters describe the beer as “heavier” in body. Isobutyl alcohol is another contributor. Brewers carefully control fermentation temperature, yeast cell counts, and oxygen levels to keep these compounds in balance. Higher fermentation temperatures and longer tank-filling times generally push fusel alcohol levels up.
Gluten
Standard barley-based beer contains gluten, because barley is a gluten-containing grain. Wheat beers carry even more. The international threshold for a “gluten-free” label is below 20 parts per million (ppm). Testing of conventional beers shows that most exceed this cutoff, though roughly 15 out of 65 conventional beers in one study tested below 20 ppm without any special processing. Beers specifically brewed to be gluten-free use grains like sorghum, rice, or millet, or they use enzymes to break down gluten proteins after brewing. If you have celiac disease, relying on standard beer to fall below the threshold is not reliable.
Clarifying Agents and Additives
Many beers go through a clarifying step before packaging. Brewers add fining agents to pull suspended proteins and yeast out of the liquid, producing a clearer final product. Irish moss, a type of seaweed, is one of the most common. It’s added during the boil to accelerate protein clumping, which helps prevent the haze that can appear when beer is chilled. Isinglass, derived from fish bladders, is another traditional fining agent used primarily in cask ales. Gelatin and silica gel are also used. These agents bind to particles and settle out, so very little remains in the finished beer, but trace amounts can persist. This matters if you follow a vegan diet or have specific allergen concerns, since isinglass and gelatin are animal-derived. Many craft breweries now skip these agents entirely or use plant-based alternatives.