Reading about Food and Digestive Systems

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Food and Nutrients


Ironically, people often say “to our health” when they drink alcohol; which is bad for our health. In this chapter we will cover food, drink and their effects on our health.


You are what you eat. What you eat gives you the energy to do what you do, the building blocks to build and repair yourself, and to keep all your systems running well (maintain homeostasis). Does that mean that if you eat nothing but beef you will start mooing? No! But it does mean that if your diet is healthy (contains the energy, building blocks, and nutrients you need in the right amounts) then chances are you will be healthy.


A diet is simply the sum of the food and drink consumed considered in terms of its effect on health. When we say “diet” now-a-days we immediately think of a regimen for becoming more healthy (usually losing weight). However, in this chapter on food and its effects on our bodies we will use the word diet to simply mean the sum of food and drink consumed.


In this chapter we will consider several things:


  • Why we drink and eat.
  • What we drink and eat.
  • What happens to our food and drink after we put it in our mouths.

The Six Nutrients

Nutrients are the molecules our body needs for:


a.) Energy


b.) To build and repair itself


c.) To maintain homeostasis


There are six types of nutrients which the body needs:


1.) Protein: Proteins are made up of smaller molecules—called amino acids—which are strung together and then folded into a three-dimensional shape. Proteins are the main build blocks of our tissues, they help fight bacteria and other harmful invading organisms and molecules, they are also involved in many biological processes in the body from cell signaling to carrying oxygen in the blood. They are very important. High concentrations of protein are found in meat as well as nuts and some vegetables. It is important not only to get the right quantities (~34 grams/day) but also all essential amino acids. The best way to ensure a balanced protein diet is to eat both plant and meat high protein sources.


2.) Carbohydrates: These are found in things like bread, potatoes, and sugar. They include sugars, starches, and fiber. They provide energy. There are two types of fiber; water-soluble and water-insoluble. Soluble fiber helps maintain blood-sugar levels. Insoluble fiber helps move food-waste through the digestive system.


3.) Lipids: Fats. Lipids have many functions in the body; from storing energy to making up the cell-membrane in cells. Lipids also help the blood clot, protect nerves, and control blood pressure. Fat is an important part of the diet, but only in small quantities. Consuming too much fat can result in obesity as well as diseases such as type 2 diabetes.


4.) Vitamins: Vitamins help maintain homeostasis by acting as key elements of biochemical functions in the body. A common example of a vitamin is vitamin C—found in oranges.


5.) Minerals: Like vitamins, minerals do not provide energy, but play important roles in bodily functions. A common example is fluoride, which (among other functions) helps maintain dental health.


6.) Water: Yes, it is a nutrient! Up to 60% of the human body is water. What percent of the brain is water, you ask? 70%! We can only last for a couple days without water. Making sure to get enough water each day is essential—especially when it is warm out and/or you are exercising!


Summary

Eating and drinking are essential parts of our life. Part of maintaining a healthy lifestyle is making sure to eat and drink the right quantities of the six essential nutrients. Those nutrients are: protein, carbohydrates, lipids, vitamins, minerals, and water.


Creating a Healthy Diet



The specific advice of the USDA is:


  1. Balance calorie intake. Enjoy your food, but eat less. Avoid oversized portions.
  2. Eat certain foods. Make half your plate fruit and vegetables. Make at least half your grains whole grains. Switch to fat-free or low fat (1%) milk.
  3. Eat certain foods in moderation. Compare sodium in foods like sodium, bread, and frozen meals—and choose the foods with lower numbers. Drink water instead of sugary drinks.

Protein

According to the USDA: All foods made from meat, poultry, seafood, beans and peas, eggs, processed soy products, nuts, and seeds are considered part of the Protein Foods Group.


The key to choosing the healthy proteins is limiting the fat. On meats the percentage is often listed (for example, 96% lean meat, 4% fat).


Grains

According to the USDA: Any food made from wheat, rice, oats, cornmeal, barley or another cereal grain is a grain product. Bread, pasta, oatmeal, breakfast cereals, tortillas, and grits are examples of grain products. 


Grains are divided into 2 subgroups, whole grains and refined grains. Whole grains contain the entire grain kernel ? the bran, germ, and endosperm. For example: whole-wheat flour, bulgur (cracked wheat), oatmeal, whole cornmeal, and brown rice.


Refined grains have been milled, a process that removes the bran and germ. This is done to give grains a finer texture and improve their shelf life, but it also removes dietary fiber, iron, and many B vitamins.


Some examples of refined grain products are white flour, degermed cornmeal, white bread ad white rice.


Most refined grains are enriched. This means certain B vitamins (thiamin, riboflavin, niacin, folic acid) and iron are added back after processing. Fiber is not added back to enriched grains. Check the ingredient list on refined grain products to make sure that the word “enriched” is included in the grain name. Some food products are made from mixtures of whole grains and refined grains.”


Vegetables

According to the USDA: Any vegetable or 100% vegetable juice counts as a member of the Vegetable Group. Vegetables may be raw or cooked; fresh, frozen, canned, or dried/dehydrated; and may be whole, cut-up, or mashed.


There are five subgroups of vegetables. They are (according to chooseMyPlate.gov):


  1. Dark green vegetables (broccoli, lettuce, kale, spinach, etc)
  2. Starchy vegetables (corn, green peas, potatoes, etc.)
  3. Red & Orange Vegetables (winter squash, tomatoes, peppers, yams, etc)
  4. Beans and peas (chickpeas, kidney, lentils, split peas, black beans)
  5. Other vegetables (artichokes, asparagus, avocado, celery, beets, cucumbers, onions, zucchini, etc)

Fruits

According to the USDA: Any fruit or 100% fruit juice counts as part of the Fruit Group. Fruits may be fresh, canned, frozen, or dried, and may be whole, cut-up, or pureed.


Dairy

According to the USDA: All fluid milk products and many foods made from milk are considered part of this food group. Most dairy choices should be fat-free or low-fat. Foods made from milk that retain their calcium content are part of the group. Foods made from milk that have little to no calcium, such as cream cheese, cream, and butter, are not. Calcium-fortified soymilk (soy beverage) is also part of the Dairy Group.


Selection Tips: Choose fat-free or low-fat milk, yogurt, and cheese. If you choose milk or yogurt that is not fat-free, or cheese that is not low-fat, the fat in the product counts against your maximum limit for “empty calories” (calories from solid fats and added sugars).


If sweetened milk products are chosen (flavored milk, yogurt, drinkable yogurt, desserts), the added sugars also count against your maximum limit for “empty calories” (calories from solid fats and added sugars).


For those who are lactose intolerant, smaller portions (such as 4 fluid ounces of milk) may be well tolerated. Lactose-free and lower-lactose products are available. These include lactose-reduced or lactose-free milk, yogurt, and cheese, and calcium-fortified soymilk (soy beverage). Also, enzyme preparations can be added to milk to lower the lactose content. Calcium-fortified foods and beverages such as cereals, orange juice, rice milk, or almond milk may provide calcium, but may not provide the other nutrients found in dairy products.



Check labels

A great way to manage what you consume is to check the nutrition facts on the labels. When you read the labels, try to think of how the nutrients fit into MyPlate.


Also important is the ingredient list. The ingredients are listed from most used to least used. If you see corn syrup at the top of the ingredients it means that the greatest percentage is the percentage of corn syrup compared with the rest of the ingredients.


Exercise

Staying healthy means more than just eating healthy—it also means getting regular exercise every week. Sixty minutes of exercise at least three times a week supports healthy eating habits. So, get out there! Throw a ball! Go for a walk! Get some of your friends together and create your own game! Exercise!


Leading a healthy lifestyle means consuming the right quantities of nutrients and getting weekly exercise. The United States Department of Agriculture suggests the recommendations found at chooseMyPlate.gov. Eating healthy also means getting at least three days of exercise in every week.


What Happens to Food after You Put it in Your Mouth: The Digestive System

So far, we’ve talked about the food and drinks we need. What happens to those meals when they enter our mouths?


  1. Digestion. Digestion involves the breakdown of what we consume into nutrients. The first step is mechanical digestion—chewing. After we mechanically break down the food with our teeth, we begin chemical digestion. Chemical digestion breaks down what we eat and drink chemically. Chemical digestion is mostly accomplished by proteins called enzymes.
  2. Absorption. After we’ve broken down the nutrients we need, we absorb them into our body. This step is called absorption.
  3. Elimination. Lastly, we excrete solid and liquid waste.

Enzymes

Enzymes make reactions go faster—they are catalysts. They are found at every important step of digestion. Here are some of the key enzymes:


  • Amylase is found in our saliva (in our mouths). It helps breaks down bread-like things (starches) into smaller sugar molecules.
  • Pepsin helps us digest protein in our stomachs.
  • Pancreatic lipase breaks down fats. It is secreted by the pancreas.

Hormones

What is happening when we feel hungry? Or when we feel thirsty? What we are feeling is hormones signaling our brains that we need food or we need water. Hormones—made by the endocrine system—play a large role in our digestion process. They help maintain homeostasis by stimulating appetite, thirst, as well as many, many other bodily functions.


Digestive Organs

The digestive system is essentially one long tube. It begins with the mouth and ends with the anus. On average, it is thirty feet long! In between the mouth and anus are many organs which play various roles; esophagus, stomach, small intestine, large intestine, and anus, to name a few.


Food is moved through the tube via muscle contractions. The muscle contractions start in the esophagus and end in the anus; moving in a wave called peristalsis. Peristalsis is the name of the movement of the muscle contractions moving the food through the tube.


Mouth to Stomach

Digestion begins in the mouth. In the mouth, the teeth digest food mechanically, and the saliva digests starches chemically. And so begins the journey.


After the mouth, the food travels to the stomach through a narrow tube called the esophagus. The esophagus moves the ball of chewed and partially digested food via peristalsis into the stomach.


Once in the stomach, the food is further chemically digested. The protein is digested with the enzyme pepsin. Pepsin, along with other chemicals such as hydrochloric acid (HCl) chemically digest the food. Water, salts, and simple sugars are absorbed through the walls of the stomach. The rest of the nutrients are absorbed after exiting the stomach.


 The small intestine

The small intestine is about 7ft long in adults and is composed of three parts. Even though it’s only seven feet long, if it were spread out it would cover a basketball court!


  1. The duodenum. The duodenum is the first part of the small intestine. In the duodenum the food from the stomach is further digested (chemically). Some of the chemicals are secreted from the duodenum itself, others are secreted from the liver and pancreas.
  2. The jejunum. Most nutrients are absorbed into the body at this second part of the small intestine. The nutrients are absorbed through tiny blood vessels.
  3. The ileum. Here nutrients are also absorbed into the blood stream. What is not absorbed in the ileum is passed as waste through the large intestine.


The Large Intestine

The large intestine takes the liquid waste from the small intestine, absorbs the excess water, and excretes the solid was through the anus.


The large intestine is home to trillions of helpful bacteria. Although we often think of bacteria as harmful, we want the bacteria in our small intestines. We have a symbiotic relationship with the bacteria in our small intestines—we help each other to live. Among other functions, the bacteria in our large intestines produce vitamins B12 and K, as well as break down poisons.


The Liver

The liver is essential to digestion, and life. The liver detoxifies the blood, maintains the glucose  balance, synthesizes proteins, and produces many chemicals needed for digestion. The liver is essential to life perhaps that is why it is called the liver.


Maintaining a Healthy Digestive System

Keeping your digestive system healthy involves several things:


  • Eating healthy food; making sure to get all the right nutrients and fiber.
  • Taking care of yourself if you contract a foodborne illness.
  • Drinking lots of water.

Getting the right nutrients and getting fiber in your diet is extremely important. The nutrients keep your system running well, while fiber helps to move waste through your digestive system. If you do not get enough fiber you may become constipated; unable to pass waste.


Foodborne illnesses usually result from food or drink contaminated by harmful bacteria. This often results in diarrhea. To avoid foodborne illness you can:


  • Always wash your hands after you go to the bathroom.
  • Always wash your hands before you eat.
  • Make sure that meats, fish, poultry, and eggs are thoroughly cooked before you eat it.

Food allergies

Food allergies can be dangerous, even deadly. Common food allergies are: peanut, eggs, fish, milk, and shellfish. If you suspect that you have a food allergy, a medical doctor could be able to check.


Some peoples’ bodies cannot break down certain chemicals. These are called intolerances. A common intolerance is lactose intolerance—an inability to break down lactose found in dairy products. Seventy five percent of the world is lactose intolerant.


Summary

Digestion is the process of food (and drink) being broken down and absorbed. The mouth begins the digestion by breaking down food mechanically and beginning chemical digestions. Protein is digested in the stomach. The small intestine finishes the chemical digestion and absorption of food. The large intestine absorbs excess water from the waste and finally passes it through the anus.


Maintaining a healthy digestive system means


a.) maintaining a healthy diet, and


b.) taking care of any illnesses, allergies, or intolerances which arise.


Click here to get started with the experiments for this lesson!

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Comments

10 Responses to “Reading about Food and Digestive Systems”
  1. Aurora says:

    Thanks for letting us know – I am surprised there are so many as we had a professional editing company proof our material before publishing. Thank you for letting us know, and I did get the previous message and had it re-done as requested. I do apologize for the errors – I know how distracting it can be when language is not correct.

  2. lynn_mcaleece says:

    Please fix the many typographical errors on this page. I’ve submitted separate suggests via “Contact Us,” suggesting that I notify you when I see typos, but I don’t have time to point out the many on every page, nor should I have to do so when I am paying for this subscription. I would expect that you would have staff to do that job. That there are so many typos reduces the credibility of the information you are trying to present. It’s very distracting.

  3. Marie Warren says:

    If the small intestine is only 7ft. long how can it cover a basketball court, please explain.

  4. Marie Warren says:

    Overall it was a good article

  5. Marie Warren says:

    I must agree with William Burdett. Also most of the information on the digestive system i learned in fifth grade.

  6. Aurora says:

    Our cells are happiest when they are in their normal or “home” state. This is a state in which the temperature, the concentrations of molecules, and molecules being produced are all at the levels at which they normally function. This “normal” or “home” state is called homeostasis.

    Read more about it here:
    https://www.sciencelearningspace.com/2011/11/positive-and-negative-feedback-loops/

  7. Lorelei Grecian says:

    What is homeostasis?

  8. Sophia Pitcher says:

    That is a neat article! 🙂 ~jasmin

  9. Aurora says:

    Thank you so much for your comments. While I recognize that government agencies can be influenced by lobbyists, the prevailing belief in the scientific community is that USDA recommendations have been tested and shown to be true through observational tests. You might be interested this article “What Should I Eat?” that suggests the Omni-Heart Diet for nutrition. This diet is based on scientific trials and the results are published in a journal that does not accept advertising.

  10. William Burdett says:

    I would like to strongly encourage you to remove the nutritional information from the digestive system material. 1)the digestive system biology including the many components and their various functions are fascinating and can be gone into with more detail especially focusing on things like microvilli, pancreas, liver, etc.etc. 2)nutrition information should be a separate unit so that it can also go into more complete detail 3) the nutrition information you have chosen to include in this section currently is very politically charged (yes, it is, much like if you were to begin the section on skin with a sentence such as “global warming increases the temperature making us sweat”) The USDA food pyramid and “My Plate” information is based on faulty information maintained over decades by agricultural lobbies, pharmaceutical companies and even the FDA. Better and more accurate information can be found from independent sources such as The Weston A. Price Foundation, the Nutritional Therapy Association and its members, George Mateljan Foundation or mercola.com. 4) excellent information on the intricacies of the digestive system focusing on the multitude of environmental and food components that destroy healthy digestive tracts can be found in the book Gut And Psychology Syndrome and http://www.gaps.me

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