Is Buttermilk the Same as Whey Protein? No, Here’s the Difference

January 12, 2026 •

3 min read

Despite both being dairy byproducts, buttermilk and whey protein are fundamentally different products with distinct origins, nutritional values, and applications. While buttermilk is a fermented drink that results from churning butter, whey is the liquid separated from milk during cheesemaking.

Quick Summary

Buttermilk, a tangy fermented dairy drink, differs significantly from whey protein, a liquid byproduct of cheesemaking. They vary in production method, protein concentration, fat content, and bioactive compounds, serving different purposes in nutrition and cooking.

Key Points

Different Origins: Buttermilk comes from churning butter or culturing milk, while whey is a byproduct of cheesemaking.
Fermentation Matters: Cultured buttermilk is fermented by bacteria, giving it a tangy taste and probiotic properties, which is not the case for whey.
Protein Concentration: Whey protein supplements offer a much higher concentration of protein per serving compared to liquid buttermilk.
Distinct Nutrients: Buttermilk contains the unique Milk Fat Globule Membrane (MFGM), while whey is known for its fast-digesting bioactive peptides.
Differing Uses: Buttermilk is a culinary staple for cooking and baking, whereas whey protein is primarily used as a dietary supplement for fitness.
Texture and Flavor: Buttermilk is a thick, tangy liquid, while powdered whey protein is tasteless until flavored and mixed into a shake.

Production Methods: The Origins of Each Dairy Product

Understanding how buttermilk and whey are made is the first step to recognizing their differences. Buttermilk’s origin depends on whether it is traditional or cultured. Traditional buttermilk is the leftover liquid from churning butter out of cream, while modern cultured buttermilk is made by adding lactic acid bacteria to milk. This fermentation process thickens the milk and gives it its characteristic tangy flavor.

Whey, in contrast, is the translucent, watery liquid that separates from the milk solids (curds) during the cheesemaking process. When milk is curdled using rennet (for sweet whey) or an acid (for acid whey, like that from Greek yogurt), the whey is strained off. This liquid is then further processed, concentrated, and dried to create the whey protein powders widely available as dietary supplements.

Fermentation: A Key Distinguishing Factor

The presence of fermentation is another critical distinction. Cultured buttermilk is a fermented dairy product, containing lactic acid bacteria that aid in digestion and have other probiotic benefits. The lactose content is lower in fermented buttermilk because the bacteria convert some of the lactose into lactic acid. Whey, while it does contain lactose, is not a fermented product in the same way. The fermentation of buttermilk gives it a unique nutritional profile and taste compared to whey.

Nutritional Comparison: Buttermilk vs. Whey Protein

At a glance, both buttermilk and whey come from milk and contain protein, but a closer look at their nutritional makeup reveals substantial differences. Buttermilk is a balanced dairy drink containing protein, carbs, and fat, along with minerals like calcium and vitamins. Whey protein, especially in its concentrated or isolated form, is specifically processed to maximize protein content and minimize fat and lactose.

Composition Breakdown

Buttermilk (per 1 cup low-fat): ~98 calories, 8 grams protein, 3 grams fat, 12 grams carbs.
Whey Protein (per 1 scoop isolate): ~120 calories, 30 grams protein, minimal fat and carbs.

Bioactive Compounds

Buttermilk contains unique components like the Milk Fat Globule Membrane (MFGM), which is released during the churning process. The MFGM is rich in bioactive compounds with potential health benefits, including cholesterol-lowering effects. Whey contains whey proteins, which are a source of bioactive peptides that are quickly digested and absorbed by the body.

Usage and Application: Culinary vs. Supplemental

The practical application of these two dairy products further highlights their differences. Buttermilk is primarily a cooking and baking ingredient, valued for its tangy flavor and ability to tenderize meats or create fluffy baked goods. It's also enjoyed as a refreshing, nutrient-rich beverage. Whey protein, by contrast, is a dietary supplement specifically for increasing protein intake, particularly for athletes, bodybuilders, and those focused on muscle growth and recovery.

Comparison Table


Feature	Buttermilk	Whey Protein
Origin	Byproduct of butter production or cultured from milk.	Byproduct of cheesemaking.
Production	Involves fermentation with lactic acid bacteria.	Processed from liquid whey separated during curdling.
Protein Content	Lower protein density (approx. 8g per cup).	High protein concentration (approx. 30g per scoop isolate).
Fat Content	Varies by type (low-fat cultured is common) but typically contains some fat.	Low to zero fat, especially in isolate form.
Key Components	Contains Milk Fat Globule Membrane (MFGM).	Rich in fast-digesting whey proteins like $\beta$-lactoglobulin and $\alpha$-lactalbumin.
Primary Use	Culinary ingredient for cooking, baking, and dressings.	Dietary supplement for muscle building and repair.
Texture	Thicker, creamier, and tangy (cultured).	Powdered form, mixed into a shake; liquid whey is watery.

Conclusion: Not Interchangeable, but Both Valuable

In conclusion, while both are valuable dairy byproducts, buttermilk and whey protein are far from the same. Buttermilk offers a balanced nutrient profile and unique compounds from its fermentation and churning process, making it a versatile and healthful food ingredient. Whey protein, on the other hand, is a highly concentrated and efficiently processed protein supplement designed for specific athletic and nutritional goals. Their distinct origins and nutritional compositions mean they serve different purposes and should not be used interchangeably.

Resource: For more detailed scientific analysis comparing whey and buttermilk, see the National Institutes of Health research overview on the "Valorisation of Whey and Buttermilk for Production of Functional Beverages".

Frequently Asked Questions

The primary difference is their origin. Buttermilk is the liquid left over from churning butter or cultured milk, while whey is the liquid separated from milk during cheesemaking.

No, buttermilk cannot be used as a direct substitute for whey protein powder, especially for high-protein intake needs. Whey protein is a highly concentrated supplement, whereas buttermilk is a dairy beverage with a much lower protein content.

Yes, buttermilk does contain protein. A standard one-cup serving of low-fat buttermilk contains about 8 grams of protein.

For muscle building, whey protein is more effective due to its high concentration of fast-digesting protein and amino acids, which are crucial for post-workout muscle repair and growth.

Yes, cultured buttermilk contains probiotics (lactic acid bacteria) from the fermentation process, which can be beneficial for gut health and digestion.

Buttermilk has a distinct tangy or sour taste due to its fermentation. Unflavored whey protein powder has a neutral taste, although many supplements are sweetened and flavored.

Yes, they contain different bioactive compounds. Buttermilk is noted for the Milk Fat Globule Membrane (MFGM), while whey is known for its bioactive peptides.