Difference Between Lactose and Dairy

The main difference between lactose and dairy is that the lactose is a disaccharide included in milk while dairy refers to products made up of milk. Furthermore, glucose and galactose are the two monosaccharides in lactose while the two main types of proteins in dairy products are casein and whey.

Lactose and dairy are two components of a healthy diet. It is important to note that the absence of lactase enzyme, which digests lactose in the body, causes lactose intolerance while an abnormal immune response to the proteins in the dairy products causes milk allergy.

Key Areas Covered

1. What is Lactose
     – Definition, Structure, Importance
2. What is Dairy
     – Definition, Structure, Importance
3. What are the Similarities Between Lactose and Dairy
     – Outline of Common Features
4. What is the Difference Between Lactose and Dairy
     – Comparison of Key Differences

Key Terms

Casein, Dairy, Disaccharide, Lactose, Lactose Intolerance, Milk Allergy, Whey

Difference Between Lactose and Dairy- Comparison Summary

What is Lactose

Lactose is the principle sugar found in the mammalian milk supplied to the newborns. Around 2-8% of milk comprises lactose by weight. It is a disaccharide made up of two monosaccharides: glucose and galactose. Lactase is the enzyme responsible for the breakdown of β-1→4 glycosidic linkage between the two monosaccharides. Both glucose and galactose are hexoses used in various metabolic pathways of the body including energy production.

Difference Between Lactose and Dairy_Figure 01

Figure 1: Lactose

Lactose plays an important role in the absorption of calcium, copper, zinc, and phosphorus. The undigested lactose is used by intestinal microbiota. Lactose promotes the growth of bifidobacteria in the gastrointestinal tract. On the other hand, lactose is one of the main sources of galactose, which plays a role in the development of the brain and nervous system.

However, 65% of the human population cannot digest lactose due to the absence of the enzyme lactase. The symptoms of lactose intolerance include stomach pain, gas and bloating, nausea, and diarrhea.

What is Dairy

Diary refers to the products made up of mammalian milk. Some dairy products include butter, cheese, yogurt, ice cream, milk, etc. They are important for building healthy bones and healthy weight. They promote the health of the teeth and reduce the risk of gum disease. The two main types of proteins found in them are casein and whey. The amino acid composition of casein is good for the growth and development of young. The two main types of whey proteins are ß-lactoglobulin and a-lactalbumin. The main form of carbohydrates in dairy products is lactose. Apart from that, dairy products are rich in calcium, vitamin D and A, magnesium, and zinc. Calcium plays a major role in the formation of bones and blood clotting.

Difference Between Lactose and Dairy_Figure 02

Figure 2: Diary products

The major issues with dairy products are lactose intolerance and milk allergy. The common symptoms of milk allergy include digestive problems including bloating and diarrhea. Anaphylaxis is a life-threatening condition of milk allergy, which can block breathing by narrowing the airways. Milk allergies occur due to the failure the of immune system to recognize milk proteins.

Similarities Between Lactose and Dairy

  • Lactose and diary are two components of our diet.
  • Both are important in the functioning of the body.
  • They are intolerable for some individuals.

Difference Between Lactose and Dairy


Lactose refers to a sugar present in milk, which is a disaccharide containing glucose and galactose units while dairy refers to a product containing or made from milk.


Lactose is made up of glucose and galactose while casein, whey, lactose, calcium, vitamin D and A are the components of dairy products.


Furthermore, the lactose enhances the absorption of calcium and phosphorus and is good for gastrointestinal microbiota while dairy products are good for healthy bones as well as healthy weight.

Allergic Conditions

The absence of the lactase enzyme in the body causes lactose intolerance while the immune reactions of the body towards milk proteins causes milk allergies.


Lactose is the main sugar found in milk while dairy products are the products containing or made up of milk. The two monosaccharides in lactose are glucose and galactose while dairy products contain casein, whey, lactose, calcium, vitamin D and A. The main difference between lactose and dairy products is their relationship with milk and their importance.


1. “What Is the Function of Lactose?” Yogurt in Nutrition, 9 Apr. 2018, Available Here
2. Kalicki, Beth, and Heli J. Roy. “The Importance of Dairy Products.” Pennington Nutrition Series No 79 , Available Here

Image Courtesy:

1. “Beta-D-Lactose” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia 
2. “625547” (CC0) via Pxhere

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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