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Buttermilk is a tangy, slightly thick dairy drink that bakers prize for tender pancakes, biscuits and fried chicken coatings. The name causes confusion: it has little butter in it. Traditional buttermilk was the liquid left after churning butter, while the buttermilk in US stores today is almost always cultured buttermilk, made by adding lactic acid bacteria to pasteurized milk. This guide answers what is buttermilk under federal rules, shows USDA buttermilk nutrition values with Daily Value percentages, explains the difference between live cultures and probiotics, and gives a simple buttermilk substitute from a university extension source.
Peptide Labs does not sell buttermilk or dairy products. This article is general nutrition information, not medical advice.
Key Takeaways
- Store buttermilk is cultured milk; federal rules let it be named cultured buttermilk (21 CFR 131.112).
- Traditional buttermilk was the soured liquid left over from churning butter.
- USDA lists a cup of lowfat cultured buttermilk at 98 calories, 8.1 g protein and 22% DV calcium.
- Buttermilk has more sodium than plain milk in USDA data, because salt is a permitted ingredient.
- Cultured does not mean probiotic; a probiotic claim needs specific live microbes with evidence.
- A common buttermilk substitute is milk plus lemon juice or vinegar, left to stand a few minutes.
What is buttermilk?
There are two answers, one historical and one modern. California’s dairy board, an instrumentality of the state’s Department of Food and Agriculture, explains that buttermilk “was originally produced while making butter.” Milk and cream often soured slightly from naturally occurring bacteria before and during churning, and the thin, tangy liquid left after the butter formed became buttermilk.
Modern cultured buttermilk is made differently. According to the same source, it is made from pasteurized nonfat or low-fat milk to which a lactic acid culture is added to produce acid that thickens and flavors it. The bacteria turn some of the milk sugar into lactic acid, which thickens the milk and gives the familiar sour taste.
What the federal standard says
The US Food and Drug Administration covers this product in its standard for cultured milk, 21 CFR 131.112. Cultured milk is produced by culturing dairy ingredients “with characterizing microbial organisms,” must reach a acidity of at least 0.5 percent expressed as lactic acid, and “shall be pasteurized or ultra-pasteurized prior to the addition to the microbial culture.” The naming rule says that when lactic acid-producing organisms are used, the food may be named “cultured buttermilk.” The same rule mentions kefir cultured milk and acidophilus cultured milk as other traditional names; our kefir guide covers that cousin, which also uses yeasts.
The base standard sets at least 3.25 percent milkfat, and the label names lower-fat versions with a fat descriptor, such as the lowfat cultured buttermilk that USDA lists. Optional ingredients allowed by the rule include nonfat dry milk, whey, stabilizers, butterfat or milkfat flakes, citric acid, sweeteners, flavoring and salt. Flecks in some cartons may be added butterfat flakes, and the salt helps explain the sodium numbers below.
Buttermilk nutrition facts
Lowfat cultured buttermilk is the most common type in US stores, so it leads the table. Values are for one cup, the portion USDA lists.
| Nutrient (lowfat cultured buttermilk, FDC 170874) | Per 1 cup (245 g) | % Daily Value |
|---|---|---|
| Calories | 98 | n/a |
| Protein | 8.1 g | 16% |
| Total fat | 2.6 g | 3% |
| Saturated fat | 1.6 g | 8% |
| Cholesterol | 10 mg | 3% |
| Carbohydrate | 11.7 g | 4% |
| Calcium | 284 mg | 22% |
| Phosphorus | 218 mg | 17% |
| Potassium | 370 mg | 8% |
| Sodium | 363 mg | 16% |
| Riboflavin (vitamin B2) | 0.38 mg | 29% |
| Vitamin B12 | 0.54 mcg | 22% |
| Vitamin D | 0 mcg | 0% |
Source: USDA FoodData Central, SR Legacy, FDC 170874. %DV uses FDA Daily Values for a 2,000-calorie reference diet.
The pattern is close to lowfat milk: a good share of calcium, riboflavin and vitamin B12, moderate protein, and little fat. Two details differ. First, USDA lists no vitamin D for cultured buttermilk, while fortified fluid milk carries it. Some brands may add vitamin D, so the Nutrition Facts panel is the place to check. Second, sodium is noticeably higher than in plain milk. If you track salt, our low sodium foods guide explains how to read sodium on labels.
Lowfat, reduced fat and whole buttermilk vs milk
| Per 1 cup (FDC ID) | Calories | Fat | Saturated fat (%DV) | Protein | Calcium (%DV) | Sodium (%DV) | Vitamin D (%DV) |
|---|---|---|---|---|---|---|---|
| Lowfat cultured buttermilk (170874) | 98 | 2.6 g | 1.6 g (8%) | 8.1 g | 284 mg (22%) | 363 mg (16%) | 0 mcg (0%) |
| Reduced fat cultured buttermilk (167697) | 137 | 4.9 g | 3.0 g (15%) | 10.0 g | 350 mg (27%) | 257 mg (11%) | 0 mcg (0%) |
| Whole buttermilk (172225) | 152 | 8.1 g | 4.7 g (23%) | 7.9 g | 282 mg (22%) | 257 mg (11%) | 3.2 mcg (16%) |
| Whole milk, 3.25%, vitamin D added (171265) | 149 | 7.9 g | 4.6 g (23%) | 7.7 g | 276 mg (21%) | 105 mg (5%) | 3.2 mcg (16%) |
Source: USDA FoodData Central, SR Legacy. Cup weights are 245 grams for buttermilk and 244 grams for milk.
The Dietary Guidelines for Americans 2020-2025 list buttermilk in the dairy group along with milk, yogurt, kefir and cheese, and note that most dairy choices should be fat-free or low-fat. The 2025-2030 edition says to include full-fat dairy with no added sugars when consuming dairy, and both editions keep saturated fat under 10 percent of daily calories. For more calcium options, see our foods high in calcium list.
Live cultures vs probiotics
Because buttermilk is cultured, it is often described as a probiotic food. The science groups are more careful. A 2021 consensus statement from the International Scientific Association for Probiotics and Prebiotics (ISAPP) separates fermented or cultured foods from probiotics. Under that framework, a food can be called a source of live and active cultures only if it has not been processed to remove or kill the microbes, and it should only be labeled as containing probiotics when its live microbes are defined and have evidence of a health benefit.
Culture strains in buttermilk are chosen for acid and flavor, and we found no strain-level research showing a specific benefit from store buttermilk. That does not make it a poor food; it means “cultured” and “probiotic” are different label words. Our fermented foods guide covers what research on cultured foods does and does not show, and our probiotic guide explains strain names and counts on supplement labels.
Buttermilk substitute options
Most recipes use buttermilk for its acid, which reacts with baking soda to lift batters and keeps crumbs tender. Utah State University Extension lists these swaps for one cup of buttermilk:
- Milk plus acid: 1 tablespoon vinegar or lemon juice plus enough milk to make 1 cup; let stand 5 minutes.
- Cream of tartar: 1 3/4 teaspoons cream of tartar plus 1 cup milk.
- Plain yogurt: 1 cup plain yogurt.
Dried buttermilk powder is another pantry option. USDA lists a tablespoon at about 25 calories with 2.2 grams of protein; the package explains how to mix it into a recipe.
Who should be careful with buttermilk
- Milk allergy: milk is one of the nine major food allergens under US law, and buttermilk is a milk product. Work with an allergist; our elimination diet guide explains why testing should be supervised.
- Lactose intolerance: buttermilk still contains milk sugar. NIDDK notes that many people with lactose intolerance can handle some lactose without symptoms; our lactase guide covers enzyme products.
- Raw buttermilk: FDA warns that raw milk and products made from it can carry Listeria, Salmonella, E. coli and Campylobacter. The federal standard requires pasteurization before culturing; pregnant people, young children, older adults and anyone with a weakened immune system should choose pasteurized products.
- Sodium limits: if a clinician has asked you to limit sodium, compare labels, since values vary by brand.
For other tangy dairy foods, our Greek yogurt guide and sour cream guide compare protein, fat and calcium.
Frequently Asked Questions
Is buttermilk just sour milk?
Not exactly. Store buttermilk is pasteurized milk soured on purpose with selected lactic acid bacteria. Milk that sours on its own has grown whatever microbes were present, which is a different product.
Does buttermilk have butter in it?
Very little. Lowfat cultured buttermilk has about 2.6 grams of fat per cup in USDA data. Some cartons add small butterfat flakes, which the federal standard allows.
Is buttermilk a probiotic?
Not by the ISAPP definition unless the product lists defined live microbes with evidence of benefit. Buttermilk is a cultured food; whether any cultures are still alive depends on processing.
Can I drink buttermilk if I am lactose intolerant?
Some people can, since tolerance varies. Buttermilk still contains lactose, so start small and talk with a clinician if symptoms persist.
What is the easiest buttermilk substitute?
Utah State University Extension suggests 1 tablespoon of vinegar or lemon juice plus enough milk to make 1 cup, left to stand 5 minutes.
Why does buttermilk have more sodium than milk?
Salt is an optional ingredient under the cultured milk standard. USDA lists 363 milligrams of sodium per cup of lowfat cultured buttermilk.
Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement, especially if you take medicines, are pregnant or have a food allergy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Sour Cream: Nutrition Facts and Sour Cream vs Greek Yogurt, Kefir Benefits: What Kefir Is, the Evidence and Kefir vs Yogurt, Fermented Foods: List, Benefits and Live vs Pasteurized.