Reading about Food and Digestive Systems
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 effect 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 healthier (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:
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 building 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, nuts and some vegetables. It is important not only to get the right quantities (~34 grams/day) but also to get 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. Carbohydrates 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: Also known as 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 helps maintain dental health (among other functions).
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!
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:
- Balance calorie intake. Enjoy your food, but eat less. Avoid oversized portions.
- 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.
- 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.
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 meat packaging, the percentage is often listed (for example, 96% lean meat, 4% fat).
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 which includes 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, de-germed 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.”
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):
- Dark green vegetables (broccoli, lettuce, kale, spinach, etc)
- Starchy vegetables (corn, green peas, potatoes, etc.)
- Red & orange vegetables (winter squash, tomatoes, peppers, yams, etc)
- Beans and peas (chickpeas, kidney, lentils, split peas, black beans)
- Other vegetables (artichokes, asparagus, avocado, celery, beets, cucumbers, onions, zucchini, etc)
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.
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.
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.
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?
- 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.
- Absorption. After we’ve broken down the nutrients we need, we absorb them into our body. This step is called absorption.
- Elimination. Lastly, we excrete solid and liquid waste.
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.
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.
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 and 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!
- 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.
- 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.
- 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 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
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.
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.