Posted on 11 Feb 2013 16:11
One of the claims associated with the raw food movement is that you need the "living" enzymes in raw foods to help you digest food. And furthermore, you only have a finite amount of enzymes in your body, so these enzymes from raw plant foods become more and more important to your health as you age.
Well, first, the enzymes in plants are there for the plants to use. They have nothing to do with your digestion. Yes, when you cook food the protein-based enzymes become denatured, but this is the same thing that would happen in your stomach. The proteins will be denatured and broken down into amino acids and peptides. Very few intact proteins make it through the intestinal lumen of the adult gut. And once there, for some certain people, they cause anaphylactic shock or hypersensitivity reactions. The enzymes in plants are not known to have any specific function in human nutrition although there is much conjecture in this area.
You Have Limited Enzymes
False. This is based on the idea that you are born with a supply of enzymes and that this supply gets used up as you age. It's absolute hogwash. Your body keeps making the digestive enzymes you need throughout life and secretes them as needed.
The enzymes responsible for digestion come from several sources, The salivary glands of the mouth, the stomach, the pancreas and the lining of the small intestine.
The Mouth and Stomach Enzymes
The salivary glands secrete amylase. Amylase helps start the break down of polysaccharides in the mouth. The stomach secretes pepsin which begins to break down proteins into peptides. The pancreas is beneath the stomach, kind of tucked into a loop formed by the first part of the small intestine. The pancreas has both endocrine and exocrine functions.
Do these raw foods contain enzymes that help you digest them?
The Pancreas and Its Enzymes
Exocrine glands secrete enzymes into ducts, whereas endocrine glands secrete them into the circulatory system. It is the exocrine function of the pancreas that is responsible for nutrition, since the gland empties it's digestive secretions through the large pancreatic duct into the duodenum. The pancreas puts out 1 to 1.5 quarts (1200 to 1500 ml) of "pancreatic juice" per day! So much for a limited supply. The juice contains water, sodium bicarbonate, and several digestive enzymes.
The sodium bicarbonate helps to neutralize the acids in the stomach so as to protect small intestine from this corrosive substance. The sodium bicarbonate also helps give the pancreatic juice itself the right pH, around 8, for the function of the enzymes.
The enzymes that the pancreas makes act on proteins, fats, starches, etc. in the small intestine. The enzymes are actually inactive when secreted and are activated by substances in the small intestine. For instance, trypsinogen is secreted by the pancreas and then activated to become trypsin. Trypsin then activates other digestive enzymes, as well. The pancreas makes the following digestive enzymes:
Digestive Enzymes of the Pancreas
Trypsin: cleaves peptide bonds of polypeptides and proteins
Chymotrypsin: same as trypsin
Carboxypeptidase: Cleaves peptide bonds on the carboxyl end of polypeptides
Amylase:breaks down starch molecules (polysaccharides) into maltose
Phospholipase: Cleaves fatty acids from phosphoglycerides to make monoglycerides
Lipase: Cleaves two fatty acids from triglycerides
Ribonuclease: Breaks RNA into smaller nucleotide chains
Digestive Enzymes of the Small Intestine
The epithelium (lining) of the small intestine makes enzymes responsible for the final stage of digestion. These enzymes, which are embedded in the membranes of the epithelial cells, further break down the molecules left by the pancreatic enzymes so that they are ready to be absorbed by the small intestine. Here are the small intestine enzymes and their function:
Maltase: Breaks down maltose into glucose
Sucrase: Breaks down sucrose into glucose an fructose
Lactase*: Breaks down lactose into glucose and galactose
Aminopeptidase: Breaks down peptides into individual amino acids
*There are those who do not continue to make enough lactase to break down lactose, which is the natural sugar found in milk. This causes varying degrees of lactose intolerance.
Of course, there is more to digestion than just enzymes. For instance, the liver secretes bile, a substance that is crucial to the digestion of fats. The bile emulsifies the fat, breaking down large fat globules into smaller ones so that they can be dispersed in the fluid contents of the small intestine. Without this, the lipid digesting enzymes would not be able to do much with the large globules of fat so fat would not be completely digested.
As you can see, the body is perfectly capable of making the enzymes it needs to digest food. There is no digestive function for the raw enzymes in plants, and they will be broken down by the same protein-digesting enzymes described above. Yes, sometimes very small amounts of whole proteins make it into the body, but any function or effect that they have is the subject of speculation, not fact.