Although its name implies that it is high in fat, buttermilk contains no butter and is traditionally low in fat. According to the California Milk Advisory Board, the name "buttermilk" stems from the original method of making buttermilk: buttermilk was the milk left over after churning butter. Today dairy producers create buttermilk from pasteurized milk by adding bacteria to culture (ferment) it. Therefore its nutritional profile is similar to regular milk.
Calorie and Fat Content
The calorie content of buttermilk depends on the amount of fat the milk contains. Milk producers generally use low-fat (1 percent) or reduced-fat (2 percent) milk in the production of buttermilk. According to the US Department of Agriculture National Nutrient Database for Standard Reference, buttermilk made from low-fat milk contains about 100 calories and 2g fat per cup, while buttermilk made from reduced-fat milk contains about 140 calories and 5g fat.
According to the USDA database, low-fat buttermilk contains 284 mg calcium and reduced-fat buttermilk contains 350 mg calcium. Because both contain more than 20 percent of the Daily Value for calcium--a reference amount set by the Food and Drug Administration (1000mg for age 4 and older)--buttermilk is considered high in calcium.
Like regular milk, buttermilk is also high in riboflavin, a B vitamin important for converting food into energy. The USDA database lists the riboflavin content of low-fat buttermilk as 0.4g while reduced fat buttermilk contains about 0.5g riboflavin per cup. According to the FDA, the Daily Value for riboflavin is 1.7g.
According to the USDA database, low-fat buttermilk contains 8g protein in 1 cup, the same amount found in regular milk. Reduced-fat buttermilk, however, contains 10g protein. The FDA Daily Value for protein is 50g. Because both types of buttermilk provide between 10 and 19 percent of the Daily Value for protein, it is considered a good source.
A Probiotic Food
As a fermented milk product, buttermilk is considered a probiotic food, a food that contains live microorganisms that provide health benefits. Eating probiotics helps populate your intestine with health-promoting bacteria which may improve immune function and reduce diarrhea, among other potential health benefits, according to research published in the June 2006 "Journal of Applied Microbiology."