People with Lactose intolerance don't have enough enzymes to break this down into the monosaccharide pieces of Galactose and Glucose. Instead, tiny microbes get to eat on Lactose, which in turn produce methane gas responsible for other digestional issues.

Sucrose is the molecule that makes up granulated table sugar. Sucrose is a natural 50/50 combo of Fructose and Glucose. Hi-Fructose Corn Syrup (HFCS) is 55% Fructose/45% Glucose. Both HFCS and Sucrose are added in a lot of foods we eat. The huge amount of Fructose we consume in the Standard American Diet (SAD) has been shown to be responsible for a number of our national dietary issues.

Cellulose is polymer of Glucose that plants produce to make their cell well more sturdy and rigid. On the macro scale, this ultimately becomes the hard shelled bark that protects a tree. Humans do not produce the enzyme needed to break down Cellulose into Glucose, so it passes through our digestive system as fiber.

Lactose is a disaccharide sugar composed of glucose and galactose, naturally present in the milk of mammals. Galactose is present in small amounts in some fruits and vegetables, including beets, citrus fruits, apples, brussels sprouts,  carrots. legumes and nuts. Mammals have used this unique saccharide to feed there young for millions of years.

Prolactin is the hormone that stimulates the production of lactose. Prolactin is secreted in the posterior pituitary gland. This mechanism is normally triggered by nursing, and the simultaneous release of the "love hormone" oxytocin helps stimulate further production.

Lactation is sometimes stimulated in dairy cows using prolactin and oxytocin.

Lactobacillus and Bifidobacterium ferment the lactose to produce lactic acid. Lactic acid gives cheese its signature flavor. It's also produced by our muscles after strenuous exercise.

Cheese starts with milk, which contains both lactose and proteins like casein. When milk is curdled (using rennet or acidic substances), it separates into solid curds and liquid whey. 

Bacteria are introduced in most cheese-making processes to acidify the milk and start fermentation. These bacteria consume lactose as a food source and convert it into lactic acid, which gives cheese its tangy flavor.

Fresh cheeses (such as ricotta or mozzarella) retain slightly more lactose because they undergo shorter fermentation and aging processes.

The more aged the cheese, the longer the bacteria have to consume the remaining lactose, meaning aged cheeses (like Parmesan, Cheddar, or Swiss) often have negligible lactose content, making them tolerable for most people with lactose intolerance. 

Cheese likely began around 8,000-10,000 years ago, soon after humans domesticated sheep and goats. Cheese is made when rennet or an acid is added to milk.

The earliest cheeses were probably discovered by accident when milk stored in animal stomachs (which contain rennet, an enzyme) curdled. 

Evidence of cheese-making has been found in ancient pots and strainers with milk-fat residues in archaeological sites from Poland to the Middle East (this one pictured is a 3000 year old pot cheese in Egypt)

Early records and depictions in tombs show that the Egyptians were fond of cheese, which they used in religious offerings and as a food source in the hot climate. 

Homer mentions cheese in the Odyssey, where Polyphemus, the Cyclops, stored it. The Romans spread cheese across Europe, developing more refined methods that would become the basis for cheese varieties we recognize today. 

Cheese consumption surged with the spread of refrigeration and modern dairy farming in the 20th century. Countries like France, Italy, and Greece became famous for their cheeses, and global consumption continues to rise.