#uncat 

## The Mouth
Amylase breaks down starch into managable sugars.

No protein digestion happens in the mouth

Although saliva does contain very small amounts of *lingual lipases* - fat-busting enzymes - the amount is so small fat digestion is very insignificant.

## The Stomach
Stomach juices are a potent mix of enzymes, hydrochloric acid, and mucus.

One particular enzyme, gastric alcohol dehydrogenase, digests small amounts of alcohol.
Other enzymes, plus stomach juices, begin the digestion of proteins and fats, separating them into [[Amino acids|amino acids]] and [[Fatty acids|fatty acids]]

Digestion of carbohydrates temporary halts for the most part in the stomach.

Eventually, semi-digested food, called **chyme** (химус) goes into the small intestine

## The Small Intestine
When chyme enters the small intestine, a whole set of enzymes are released:
- pancreatic and intestinal enzymes finish the digestion of proteins into amino acids
- bile enables fats to mix with water
- alkaline pancreatic juices make the chyme less acidic so that amylases can go back to work breaking down sugars
- intestinal alcohol dehydrogenase further digests alcohol

The lining of the small intestine is covered with small nipplelike "**villi**" (sg. villus), each of those is covered in microvilli. Every villus and microvillus is programmed to accept a specific nutrient - and no other.

The order in which [[Nutrients|nutrients]] are absorbed is:
1) carbohydrates
2) proteins
3) fats
4) vitamins (first those that dissolve in water, then those that dissolve in fat)

Once observed, nutrients:
- amino acids, sugars, [[Vitamin C|vitamin C]], the [[B vitamins]], iron, calcium, magnesium are carried to the liver, where they're processed and then sent to the rest of the body
- fatty acids, cholesterol, and [[Vitamin A|vitamins A]], [[Vitamin D|D]], [[Vitamin E|E]], and [[Vitamin K|K]] go into the lymphatic system and then into the blood, where they, too, end up first in liver for processing

Catabolism - the metabolic process that gives you energy
Anabolism - the metabolic process that uses nutrients to build new tissues.

## The Large Intestine
With every usable resource wrung out of your food, the rest moves in the colon, whose primary job is to absorb water from your waste and to compact it into feces, whose brown colour comes from leftover bile pigments. A third of its mass comes from the bodies of discarded microorganisms that live in the colon that:
- manufacture vitamin B12
- produce vitamin K
- break down amino acids and produce nitrogen (which gives feces their smell)
- feast on indigestibles, excreting farts

Then feces move through the rectum and out through the anus. Digestion of any one meal may take longer than a day.

Ilya Metchnikoff was among the first to recognize the health benefits from maintaing a good microflora, using Bulgarian peasants who ate yoghurt rich in microorganisms similar to those in the human gut as evidence for life longevity.

Probiotics are defined as "live microorganisms similar to the beneficial microorganisms found in the human gut". Most common ones are members of the bacterial Lactobacilli family.
Prebiotics are marketed as food for those beneficial microorganisms.