Why are there carbs in milk but not heavy cream?

November 22, 2025 •

2 min read

While regular cow's milk contains about 4–5g of lactose per 100ml, heavy cream contains significantly less, which is why there are carbs in milk but not heavy cream. The primary reason for this dramatic difference lies in how milk is processed, which separates the watery, sugar-rich portion from the fatty, low-carb cream.

Quick Summary

The discrepancy in carbohydrate content between milk and heavy cream stems from the industrial separation process. Raw milk is spun in a centrifuge, isolating the dense, watery liquid containing lactose from the lighter milk fat. The resulting heavy cream is therefore mostly fat with minimal lactose, while the remaining milk is rich in carbohydrates.

Key Points

Lactose is the carbohydrate in milk: Carbohydrates in milk are lactose, found in the water portion.
Heavy cream is mostly separated milk fat: Heavy cream is fat separated from the denser, lactose-containing liquid.
Centrifugal force is key: Centrifuges separate fat from watery liquid.
Heavy cream isn't truly zero-carb: US labeling allows rounding down small amounts to 0g.
Higher fat equals lower carbs: More fat means lower carbohydrate and lactose content.
Processing increases carbohydrate density in skim milk: Removing fat increases lactose concentration per ounce.

The Science of Milk Separation

Understanding the carbohydrate difference between milk and heavy cream hinges on milk separation. Raw milk contains water, fat, protein, and lactose. Centrifuges separate these components by density.

The Role of Lactose

Lactose, milk's main carbohydrate, is water-soluble and resides in the watery part, not the fat.

How Heavy Cream is Made

Centrifuging milk separates denser skim milk (water/lactose) from lighter cream (fat). The resulting heavy cream is over 36% fat with minimal lactose. Small servings can be labeled 0g carbs in the US due to regulations.

How Skim Milk is Made

Removing fat for skim milk concentrates non-fat solids, including lactose. This makes nonfat milk higher in carbohydrates per ounce than whole milk.

Milk vs. Heavy Cream: A Nutritional Comparison

A 100g comparison clarifies the difference:


Feature	Whole Cow's Milk (approx. per 100g)	Heavy Cream (approx. per 100g)
Fat	3.6g	38g or more
Carbohydrates (Lactose)	4.6g	2.4–3.95g
Energy (Calories)	~60 kcal	~340–380 kcal
Protein	3.4g	~3g

Implications for Low-Carb and Keto Diets

Heavy cream is favored in low-carb diets for its high fat and low carb content. Whole milk's lactose makes it generally unsuitable for strict keto. Products with higher fat have lower carbs as water and lactose are reduced.

The Misconception of 'Zero Carbs'

US labeling allows rounding down less than 0.5g per serving to zero. A standard serving of heavy cream falls below this, but larger amounts contain some carbs.

Conclusion: The Final Verdict

Milk processing separates lactose from fat, explaining why there are carbs in milk but not heavy cream. This alters their nutritional profiles. Understanding this helps manage macronutrient intake. For dairy processing details, see {Link: Dairy Processing Handbook https://www.scribd.com/document/595089758/Milk-Composition-and-Nutritive-Value}.

Frequently Asked Questions

Heavy cream contains minimal lactose, allowing it to be labeled as 0 grams of carbohydrates per serving in many countries like the US.

The main carbohydrate is lactose, a natural milk sugar.

A centrifuge spins milk, separating lighter milk fat from heavier liquid containing lactose.

Whole milk includes the watery portion containing most lactose; heavy cream is primarily fat.

Yes, heavy cream's high fat and very low carb content align with keto goals.

Yes, standard dairy milk contains lactose carbohydrates.

Lactose-free milk still has the same carbohydrate content; the lactose is broken down into simpler sugars.