The Fundamental Role of Lactose
To understand the disparity in carbohydrate content between milk and cheese, one must first understand the primary source of carbs in dairy: lactose. Lactose is a disaccharide, or milk sugar, composed of glucose and galactose. It is a highly water-soluble compound, which is a crucial detail that dictates its fate during cheesemaking. In a glass of milk, this lactose is dissolved throughout the liquid, contributing to its sweet flavor and overall carbohydrate count. The exact amount can vary slightly, but a typical serving of cow's milk contains a significant quantity of this sugar.
The Cheesemaking Process: A Carbohydrate Extraction
Cheesemaking is a process of separating milk solids from liquid, and it is this process that fundamentally alters the nutritional profile of the final product. It consists of two key stages that dramatically reduce the lactose content.
First, milk is acidified and an enzyme called rennet is added, causing the milk to curdle and separate into solid curds (casein proteins and fat) and liquid whey. The vast majority of the water-soluble lactose, along with some whey protein, remains dissolved in the whey, which is subsequently drained off. A typical cheesemaking process can remove over 90% of the original lactose in this initial separation. The remaining curds are then used to form the cheese.
Second, the residual lactose that is trapped within the curds is consumed by bacteria through fermentation. These lactic acid bacteria (LAB) convert the remaining milk sugar into lactic acid. As the cheese ages, this fermentation continues, progressively breaking down any remaining lactose. In aged cheeses, this process is so complete that the final product contains virtually no lactose at all. The fermentation of lactose is what gives many cheeses their characteristic tangy or sharp flavors.
Key Differences: Hard vs. Soft Cheeses
Not all cheeses are created equal when it comes to carbohydrate content. The amount of residual lactose depends heavily on how the cheese is made, particularly its aging process. Hard, aged cheeses undergo a longer fermentation, while softer, fresher cheeses retain more moisture and, consequently, more lactose.
Carbohydrate Content Variation in Cheese:
- Hard, Aged Cheeses (e.g., Parmesan, Aged Cheddar, Swiss): These cheeses have been aged for a significant period, allowing bacteria to ferment nearly all the lactose. They are extremely low in carbohydrates, often containing less than one gram per serving. This makes them a staple in low-carb diets.
- Soft, Fresh Cheeses (e.g., Cottage Cheese, Ricotta, Cream Cheese): These are produced with less fermentation and retain more of the watery whey, which contains lactose. As a result, their carb count is higher than that of hard cheeses, though still generally lower than milk.
- Processed Cheeses: The carb content here can vary significantly. While some may be low-carb, many contain added sugars or fillers. Always check the nutrition label.
Nutritional Comparison: Milk vs. Aged Cheddar
This table highlights the significant nutritional differences that result from the cheesemaking process, using aged cheddar as a low-carb example.
| Nutrient | Milk (per 100g) | Aged Cheddar (per 100g) |
|---|---|---|
| Carbohydrates | ~5g (All Lactose) | ~3g |
| Protein | ~3g | ~23g |
| Fat | Varies (e.g., 1g in skim milk) | ~33g |
| Lactose | ~5g | <0.1g (virtually none) |
| Calories | ~42 kcal (skim) | ~404 kcal |
| Calcium | ~125mg | ~710mg |
Dietary Implications for a Nutrition Diet
Understanding the carb differences between milk and cheese is vital for various dietary needs.
- Low-Carb and Keto Diets: For individuals following a ketogenic diet or a general low-carb plan, milk is typically avoided or used in very limited quantities due to its lactose content. Cheese, particularly hard, aged varieties, is a highly desirable and versatile food because of its high fat, moderate protein, and very low carbohydrate profile.
- Lactose Intolerance: Many people with lactose intolerance can consume aged cheeses without issue because the fermentation process removes the lactose that their bodies cannot properly digest. This allows them to benefit from the rich calcium and protein content of cheese without experiencing gastrointestinal distress. However, soft, fresh cheeses and other dairy products like yogurt contain varying amounts of residual lactose and may not be as well-tolerated.
- Nutrient Concentration: The cheesemaking process concentrates milk's nutrients into a smaller, solid form. This is why cheese is a powerhouse of protein and calcium compared to an equivalent weight of milk. However, this also means it is higher in calories and saturated fat, which should be considered when managing total intake.
Conclusion
In summary, the reason why is milk high in carbs but cheese isn't is a direct result of the cheesemaking process. The separation of lactose-rich whey from the milk solids, followed by bacterial fermentation of any residual lactose, transforms a high-lactose liquid into a low-lactose solid. This fundamental shift in composition results in two distinct dairy products with very different nutritional profiles, offering diverse options for individuals on various nutrition diets, from keto to lactose-intolerant plans. Both milk and cheese offer valuable nutrients, but their use in a diet is determined by these crucial carbohydrate differences.
Learn more about carbs in cheese from the U.S. Dairy website
