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How do Digestive Juices Work?

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  • Written By: Marco Sumayao
  • Edited By: Lauren Fritsky
  • Last Modified Date: 19 November 2016
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Digestive juices chemically break food down into components that are usable in fueling the body's metabolism. The exact chemical reaction that ensues is largely dependent on the specific juice. Stimuli from food, such as sight, smell and taste, triggers increased production of digestive juices. As food is processed in the gastrointestinal tract, juice production increases even more from the organs in proximity and combines with the food. The juices then separate the various components of food, such as sugar and protein, from each other and prepare them for absorption into the system.

Saliva is the first of the digestive juices to act upon food. Amylase—also referred to as "ptyalin"—, an enzyme found in saliva, begins digestion by catalyzing the dissolution of starch into simpler sugars. As an individual chews, saliva is mixed thoroughly into the food, acting upon the starch present and lubricating the food in preparation for other digestive processes.

Food is then swallowed and transported to the stomach, which contains gastric juice. This is considered one of the most volatile digestive juices, with hydrochloric acid being one of its primary components. The powerful acid serves to dissolve the food, while the enzymes pepsin and rennin break protein down into simpler amino acids. Potassium chloride and sodium chloride present in the juice help neutralize the acid, allowing for the safe transfer of food from the stomach into the small intestine, or duodenum.

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The duodenum contains two digestive juices: pancreatic juice and bile. Several enzymes act upon food in pancreatic juice; namely, amylase, lipase, and trypsin. The amylase in pancreatic juice, as in saliva, catalyzes the breakdown of complex sugars into simpler sugars. Lipase, on the other hand, catalyzes the breakdown of lipids through hydrolysis. In the same fashion, trypsin catalyzes the dissolution of chemical bonds in peptides to release simpler amino acids.

Bile, the second of the duodenum's digestive juices, is composed primarily of water. Roughly 10 percent of bile contains bile salts, however, which serve to emulsify droplets of fat from partially digested food into micelles. These fats, triglycerides and phospholipids are bound together to form structures known as micelles. The increased surface area created by the emulsification allows lipase in pancreatic juice to act upon the fat, breaking triglycerides down into simpler fatty acids and monoglyceride. These substances are then absorbed through the villi in the intestinal tract, to be used for the body's different metabolic processes.

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everetra
Post 8

@NathanG - I’d have to concur. We do tend to drool over the thought of eating our favorite foods. It’s part of the human condition.

Hopefully we can drool over more healthful food items however. I heard a medical doctor talk about the importance of eating vegetables and getting fruit juices in your diet.

He says that these foods contain enzymes which assist the digestive process, enabling your body to derive nutrients more easily from the food you eat. Otherwise, if all you eat is protein, then you can literally “starve” (according to this nutritionist) while you are eating!

Frankly, I think that a lot of people are in that category. At the very minimum, I think that you should make it a point to have a salad before your meal.

NathanG
Post 7

Is it really true that just looking at food will stimulate the digestive juices, as the article says? If this is true, then I suppose humans must be in the same category as Pavlov’s dog!

Well, I can attest to this from my own experience. Sometimes just thinking about a burger gets my salivary glands flowing. My body at that point is “prepping” for the experience.

I think that marketers instinctively know that this is what happens so they use a lot of visuals (photoshopped no less) in their advertising campaigns, whether in print or television advertising. It’s almost unfair in one sense, but you can’t deny that it works.

andee
Post 6

@turquoise - I think you are on to something with your comment. I don't think our stomachs were made to digest a lot of the food we eat today, and that is why so many people have stomach issues.

Some of the biggest selling over the counter medications are for digestive problems. There are many people who suffer from digestive system problems and think that by taking some medication, they are going to be OK.

What bothers me is that many of them have long term side effects and you are not really treating the reason you are having the digestive problems.

I think for a lot of people their digestive juices are overwhelmed and have a hard

time functioning properly. Many times it means we need to make dietary changes and that is never an easy thing to do.

I had a good friend who was having terrible digestion issues and he found out he was allergic to gluten. It was not easy, but he removed the gluten from his diet and all of his digestive issues went away, and he lost 20 pounds in the process.

Since he has done that, his digestive juices must be working as they should and he acts and feels so much better.

sunshined
Post 5

@honeybees - It really does take a conscious effort to slowly chew your food. I think we are so used to grabbing something to eat on the run, it is hard to slow down and enjoy the food we are eating.

Maybe that is one reason so many people have the digestive problems you mentioned. The human digestive system is complex and efficient, but probably isn't made to easily digest a lot of the chemicals and toxins we take in with our diet.

I have found that by taking an enzyme supplement this makes a difference for me. If I take these enzymes on a regular basis, along with a healthy diet, I don't get the indigestion, stomach pains and acid reflux that I used to get.

honeybees
Post 4

@burcidi - Yes, it really does make a difference how much you chew your food. I always remember my mom telling me to slow down and enjoy my food. She always encouraged us to take smaller bites and make sure we chewed our food slowly.

She must have known something about how much easier it is for our bodies to digest our food when it is mixed with the right amount of saliva.

If you ever look around and watch people when they are eating, most people gulp down their food without doing much chewing. Maybe that is another reason it is good to eat several small meals throughout the day.

When your body is not starving, you

are not as apt to swallow your food without chewing it. Usually the hungrier you are, the less you chew your food.

I have started to make a conscious effort to chew my food longer and think about how the digestive enzymes are working in my body. I am hoping that by doing this, I can prevent some of the digestion problems that a lot of my friends and family have.

turquoise
Post 3

I know that the digestive juices in our stomach are very strong. I think I heard once that it's the most acidic substance ever, even more than lemon juice or vinegar.

What I don't get is, how do the digestive juices not eat away at our stomach? Considering all the junk we eat nowadays and our stomach without complaint digesting everything that comes its way, it's surprising that it doesn't harm itself in the process.

Is the stomach made especially to deal with the digestive juices? Does anyone know how that works?

burcidi
Post 2

Saliva is a digestive juice?!

No wonder my doctor was telling me to chew my food more when I went complaining about stomach pains and indigestion. He asked me about how I eat and I told him I eat very quickly, I barely chew my food. He said that this is probably my problem.

He said chewing a lot and chewing slowly will improve my digestion. He told me to keep chewing my food until it's almost in liquid form in my mouth. It sounds kind of gross but I did that and it did help. I guess saliva helps break down food and makes it a lot easier for our stomach to handle. Who would have guessed?

ddljohn
Post 1

There was a doctor on TV yesterday and he said some interesting things about digestive system and enzymes that I had never heard about before. He said that the digestive juices of the stomach don't just work to digest food and separate the nutrients. Apparently they also separate any toxins that are in the food to throw out so that we do not get sick from them.

He said that the digestive juices separate all the beneficial nutrients and the toxins. The toxins are thrown out whereas the nutrients are passed down to the small intestine where they are absorbed for our body to use.

I think this is really cool. I never knew that digestive juices actually protect us from illness. I though that they only dealt with digestion. The human body is so interesting.

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