Buttermilk
Buttermilk: Nutrition, History and Cooking Guide
Traditional buttermilk is the liquid remaining after churning cream into butter — low in fat but carrying the flavour compounds, phospholipids, and lactic acid from the churning process. In modern commercial practice, what is sold as buttermilk is almost entirely cultured buttermilk — low-fat or skimmed milk that has been inoculated with lactic acid bacteria (Lactococcus lactis and related cultures) and allowed to ferment, producing a tangy, thickened product that mimics the flavour of traditional buttermilk. Buttermilk has deep roots in baking traditions across Ireland, Scotland, and the American South, where the acidity of buttermilk reacts with bicarbonate of soda (baking soda) to produce carbon dioxide, giving rise to soda bread, Irish brown bread, American biscuits, and Southern buttermilk pancakes. The buttermilk tradition in Irish cooking is particularly ancient — sour milk and buttermilk were staple foods in the Irish diet for centuries, used in breads, drinks, and as a everyday beverage on farms.
Nutritional Value of Buttermilk
Cultured buttermilk provides 56 kcal and 4.1 g of protein per 100 ml, with 2 g of fat — a nutritious, low-fat cultured dairy product. It provides calcium (around 116 mg per 100 ml), iodine, phosphorus, potassium, B12, riboflavin, and the beneficial lactic acid bacteria of fermented milk. The lactic acid gives it its characteristic tang and may contribute to gut health benefits typical of fermented dairy products.
Health Benefits of Buttermilk
Buttermilk provides the core nutritional benefits of milk — calcium, iodine, protein, and B12 — in a low-fat, tangy form. As a cultured product, it contains lactic acid bacteria that may support gut microbiome health, though most of these bacteria do not survive stomach acid to reach the large intestine in the quantities found in dedicated probiotic products. Its low fat content and protein content make it more satiating per calorie than many beverages. The acidity also makes it a tenderising marinade ingredient — it denatures muscle proteins and penetrates meat or poultry, producing tender results in fried chicken, buttermilk-marinated grilled meats, and similar preparations.
How to Use Buttermilk
For baking: replace regular milk with buttermilk and add bicarbonate of soda (half a teaspoon per 240 ml buttermilk) for a leavening reaction. Essential for soda bread, scones, and American biscuits. For marinades: soak chicken in buttermilk overnight before frying — the result is dramatically more tender. For dressings: buttermilk is the base of ranch dressing and blue cheese dressing. Substitute: mix 240 ml of milk with a tablespoon of lemon juice or white vinegar, stir, and leave for five minutes — an effective emergency substitute.
Buttermilk in more detail
Buttermilk is one of the most commonly misunderstood items in the dairy aisle, because the word now means the opposite of what it originally did. Traditional buttermilk is the thin liquid left behind after churning butter — a by-product, and low in fat by definition. Cultured buttermilk, which is what almost every carton sold today contains, is low-fat milk deliberately fermented with lactic acid bacteria to imitate it.
Either way, the useful property is acidity. Buttermilk has a pH low enough to react with bicarbonate of soda, and that reaction is the entire basis of soda bread, buttermilk scones, Irish farls and American biscuits — breads leavened chemically rather than with yeast. Substituting ordinary milk in those recipes gives no lift, because there is no acid for the bicarbonate to react with.
The acid does two other things. It tenderises: buttermilk is the traditional marinade for fried chicken because the acid loosens the protein structure gently over hours without the mushiness that a stronger acid like lemon juice produces. And it keeps cakes moist, by weakening gluten development.
The standard substitute — a tablespoon of lemon juice or vinegar per 250 ml of milk, left ten minutes — gets the acidity right and the flavour and body wrong. It works for soda bread and is a poor stand-in for a marinade.
Nutrients worth knowing about
At 56 kcal, 2 g fat and 4.1 g protein per 100 g, cultured buttermilk is leaner than whole milk with more protein — a genuinely favourable profile that its reputation as a baking ingredient tends to obscure.
It supplies Calcium, Phosphorus, Vitamin B12 (Cobalamin), Vitamin B2 (Riboflavin), Iodine and Potassium.
Fermentation reduces the lactose somewhat, so some people with mild lactose intolerance find buttermilk easier than milk — the reduction is partial, not complete. The salt figure of 0.26 g per 100 g is higher than plain milk's, which is worth noting if you drink it rather than bake with it.
Data note: this page does not currently display a micronutrient panel, because the source-database match has not been verified.