Inleiding

De opleiding HBO Voeding en diëtetiek is opgebouwd uit verschillende modules. We geven je met deze proefles een kijkje in twee modules van de opleiding:

1. Module: Anatomie en fysiologie voor de diëtist (kennisclip)
2. Module: Voedingsleer (theorie + vragen)

Je start zo direct met een kennisclip. Daarna lees je een interessant stuk uit het boek The Science of Nutrition. Tijdens het lezen van de lesstof kun je jezelf testen door vragen te beantwoorden. 

Start de proefles

De onderstaande kennisclip is afkomstig uit de module Anatomie en fysiologie voor de diëtist. Elke module die je volgt bij Hogeschool NTI bevat meerdere video's waarin belangrijke onderwerpen uit de module worden uitgelegd.

 

Heb je de video bekeken? Probeer dan eens onderstaande vraag te beantwoorden!

Theorie literatuur

Module: Voedingsleer

Je gaat nu een deel lezen, afkomstig uit het boek: The Science of Nutrition, Pearson Education, 2016. ISBN: 978-0-13-417509-6

Dit is een belangrijk boek dat als een rode draad door de opleiding loopt. De overige literatuur tijdens je opleiding is Nederlandstalig.

What Are Nutrients?

We enjoy eating food because of its taste, its smell, and the pleasure and comfort it gives us. However, we rarely stop to think about what our food actually contains. Foods are composed of many chemical substances, some of which are not useful to the body and others of which are critical to human growth and function. These latter chemicals are referred to as nutrients. The six groups of nutrients found in foods are (Figure 1.5)

• Carbohydrates
• Lipids (including fats and oils)
• Proteins
• Vitamins
• Minerals
• Water

As you may know, the term organic is commonly used to describe foods that are grown with little or no use of chemicals. But when scientists describe individual nutrients as organic, they mean that these nutrients contain the elements carbon and hydrogen, which are essential components of all living organisms. Carbohydrates, lipids, proteins, and vitamins are organic. Minerals and water are inorganic. Both organic and inorganic nutrients are equally important for sustaining life but differ in their structures, functions, and basic chemistry. You will learn more about these nutrients in subsequent chapters; a brief review is provided here.

Macronutrients Provide Energy

Carbohydrates, lipids, and proteins are the only nutrients in foods that provide energy. By this we mean that these nutrients break down and reassemble into a fuel that the body uses to support physical activity and basic physiologic functioning. Although taking a multivitamin and a glass of water might be beneficial in some ways, it will not provide you with the energy you need to do your 20 minutes on the stair-climber! Along with water, the energy nutrients are also referred to as macronutrients. Macro means "large"; thus, macronutrients are those nutrients needed in relatively large amounts to support normal function and health.
Alcohol is found in certain beverages and foods, and it provides energy - but it is not considered a nutrient. This is because it does not support the regulation of body functions or the building or repairing of tissues. In fact, alcohol is considered to be both a drug and a toxin.

FIGURE 1.5 The six groups of nutrients found in the foods we consume.

• Nutrients Chemicals found in foods that are critical to human growth and function.
• Organic A substance or nutrient that contains the elements carbon and hydrogen.
• Inorganic A substance or nutrient that does not contain carbon and hydrogen.
• Macronutrients Nutrients that the body requires in relatively large amounts to support normal function and health. Carbohydrates, lipids, proteins, and water are macronutrients.

Nutrition scientists in the United States typically use the metric system of measurement, but the U.S. customary system is also commonly used, especially in information for the public. Thus, it is important for anyone learning about nutrition to learn how to express and calculate both metric and nonmetric units.

Energy Is Measured in Kilocalories

The energy in foods is measured in units called kilocalories (kcal). A kilocalorie is the amount of heat required to raise the temperature of 1 kilogram (about 2.2 lb) of water by 1 degree Celsius. We can say that the energy found in 1 gram of carbohydrate is equal to 4 kcal.
Kilo- is a prefix used in the metric system to indicate 1,000 (think of kilometer). Technically, 1 kilocalorie is equal to 1,000 calories. A kilocalorie is also sometimes referred to as a large calorie or as a Calorie, written with a capital C. Because they're designed for the public, nutrition labels typically use the term calories to indicate kilocalories. Thus, if the wrapper on an ice cream bar states that it contains 150 calories, it actually contains 150 kcal.

In this textbook, we use the term energy when referring to  the general concept of energy intake or expenditure. We use the term kilocalories (kcal) when discussing units of energy. We use the term Calories with a capital "C" when presenting information about foods and food labels.

Both carbohydrates and proteins provide 4 kcal per gram, alcohol provides 7 kcal per gram, and fats provide 9 kcal per gram. Thus, for every gram of fat we consume, we obtain more than twice the energy derived from a gram of carbohydrate or protein.

Carbohydrates Are a Primary Fuel Source

Carbohydrates are the primary source of fuel for tlhe human body, particularly for neurologic functioning and physical exercise (Figure 1.6). A dose look at the word carbohydrate reveals the chemical structure of this nutrient. Carbo- refers to carbon, and -hydrate refers to water. You may remember that water is made up of hydrogen and oxygen. Thus, carbohydrates are composed of chains of carbon, hydrogen, and oxygen.

Carbohydrates are found in a wide variety of foods: rice, wheat, and other grains, as well as vegetables and fruits. Carbohydrates are also found in legumes (foods that include lentils, beans, and peas), seeds, nuts, and milk and other dairy products. Fiber is also classified as a type of carbohydrate.

FIGURE 1.6 Carbohydrates are a primary source of energy for our body and are found in a wide variety of foods

Lipids Provide Energy and Other Essential Nutrients

Lipids are another important source of energy for the body (Figure 1.7). Lipids are a diverse group of organic substances that are largely insoluble in water. In foods, they are found in solid fats and liquid oils. Lipids include triglycerides, phospholipids, and sterols. Like carbohydrates, lipids are composed mainly of carbon, hydrogen, and oxygen (and in phospholipids, phosphorus and sometimes nitrogen); however, they contain proportionately much less oxygen and water than do carbohydrates. This quality partly explains why they yield more energy per gram than either carbohydrates or proteins.

FIGURE 1.7 Lipids are an important energy source during rest and low-intensity exercise. Foods containing lipids also provide other important nutrients.

Triglycerides (more commonly known as fats) are by far the most common lipid in foods. They are composed of an alcohol molecule called glycerol attached to three acid molecules called fatty acids. As we'll discuss throughout this book, triglycerides in foods exert different health effects according to the type of fatty acids they contain. Some fatty acids are associated with an increased risk of chronic disease, whereas others ‑ including essential fatty acids ‑ protect our health.

Triglycerides are an important energy source when we are at rest and during low- to moderate-intensity exercise. The human body is capable of storing large amounts of triglycerides as adipose tissue, or body fat. These fat stores can be broken down for energy during periods of fasting, such as while we are asleep. Foods that contain lipids are also important for the absorption of fat-soluble vitamins.

Phospholipids are a type of lipid that contains phosphate. The body synthesizes phospholipids, and they are found in a few foods. Cholesterol is a form of lipid that is synthesized in the liver and other body tissues. It is also available in foods of animal origin, such as meat and eggs. Plant sterols are present in some plant-based foods such as vegetable oils.

Proteins Support Tissue Growth, Repair, and Maintenance

Proteins also contain carbon, hydrogen, and oxygen, but they differ from carbohydrates and lipids in that they contain the element nitrogen (Figure 1.8). Within proteins, these four elements assemble into small building blocks known as amino acids. We break down dietary proteins into amino acids and reassemble them to build our own body proteins ­­‑ for instance, the proteins in muscles and blood.

FIGURE 1.8 Proteins contain nitrogen in addition to carbon, hydrogen, and oxygen. Proteins support the growth, repair, and maintenance of body tissues.

You Do The Math: Calculating the Energy Contribution of Carbohydrates, Lipids, and Proteins

One of the most useful skills to learn as you study nutrition is determining the percentage of the total energy someone eats that comes from carbohydrates, lipids, or proteins. These data are an important first step in evaluating the quality of an individual's diet. Fortunately, a simple equation is available to help you calculate these values.

To begin, you need to know how much total energy someone consumes each day, as well as how many grams of carbohydrates, lipids, and proteins. You also need to know the kilocalorie (kcal) value of each of these nutrients: the energy value for carbohydrates and proteins is 4 kcal per gram, the energy value for alcohol is 7 kcal per gram, and the energy value for lipids is 9 kcal per gram. Working along with the following example will help you perform the calculations:

• Let's say you have completed a personal diet analysis for your mother, and she consumes 2,500 kcal per day. From your diet analysis you also find that she consumes 300 g of carbo­hydrates, 90 g of lipids, and 123 g of proteins.

• To calculate her percentage of total energy that comes from carbohydrates, you must do two things:

• Multiply her total grams of carbohydrate by the energy value for carbohydrate to determine how many kilocalories of carbohydrate she has consumed.
  300 g of carbohydrate x 4 kcal/g = 1,200 kcal of carbohydrate

• Take the kilocalories of carbohydrate she has consumed, divide this number by the total number of kilocalories she has consumed, and multiply by 100. This will give you the percentage of total energy that comes from carbohydrate.
  (1,200 kcal/2,500 kcal) x 100 = 48% of total energy from carbohydrate

• To calculate her percentage of total energy that comes from lipids, you follow the same steps but incorporate the energy value for lipids:

• Multiply her total grams of lipids by the energy value for lipids to find the kilocalories of lipids consumed.
  90 g of fats x 9 kcal/g = 810 kcal of lipids
• Take the kilocalories of lipids she has consumed, divide this number by the total number of kilocalories she consumed, and multiply by 100 to get the percentage of total energy from lipids.
  (810 kcal/2,500 kcal) x 100 = 32.4% of total energy from lipids
• Now try these steps to calculate the percentage of the total energy she has consumed that comes from proteins.

These calculations will be useful throughout this course as you learn more about how to design a healthful diet. Later in this book, you will learn how to estimate someone's energy needs and determine the appropriate amount of energy to consume from carbohydrates, fats, and proteins.

Although proteins can provide energy, they are not usually a primary energy source. Proteins play a major role in building new cells and tissues, maintaining the structure and strength of bone, repairing damaged structures, and assisting in regulating metabolism and fluid balance.

Proteins are found in many foods. Meats and dairy products are primary sources, as are seeds, nuts, and legumes. We also obtain small amounts of protein from vegetables and whole grains.

Now that you've been introduced to the three energy nutrients, refer to the You Do the Math (see above) to learn how to calculate the different energy contributions of carbohydrates, lipids, and proteins in one day's diet.

Micronutrients Assist in the Regulation of Physiologic Processes

Vitamins and minerals are referred to as micronutrients. That's because we need relatively small amounts of these nutrients to support normal health and body functions.

• Micronutrients Nutrients needed in relatively small amounts to support normal health and body functions. Vitamins and minerals are micronutrients.

Vitamins are organic compounds that assist in the regulation of the body's physiologic processes. Contrary to popular belief, vitamins do not contain energy (or kilocalories); however, they do play an important role in the release and utilization of the energy found in carbohydrates, lipids, and proteins. They are also critical in building and maintaiiting healthy bone, blood, and muscle; in supporting our immune system so we can fight illness and disease; and in ensuring healthy vision.

Vitamins are classified as two types: fat-soluble vitamins and water-soluble vitamins (Table 1). This classification reflects how vitamins are absorbed, transported, and stored in our body. As our body cannot synthesize most vitamins, we must consume them in our diet. Both fat-soluble and water-soluble vitamins are essential for our health and are found in a variety of foods. Fat-soluble vitamins are found in a variety of fat-containing foods, including dairy products.

TABLE 1 Overview of Vitamins

Minerals include sodium, calcium, iron, and over a dozen more. They are classified as inorganic because they do not contain carbon and hydrogen. In fact, they do not "contain" other substances at all. Minerals are single elements, so they already exist in the simplest possible chemical form. Thus, they cannot be broken down during digestion or when our body uses them to promote normal function; and unlike certain vitamins, they can't be destroyed by heat or light. All minerals maintain their structure no matter what environment they are in. This means that the calcium in our bones is the same as the calcium in the milk we drink, and the sodium in our cells is the same as the sodium in our table salt.

Minerals have many important physiologic functions. They assist in fluid regulation and energy production, are essential to the health of our bones and blood, and help rid the body of harmful by-products of metabolism. Minerals are classified according to the amounts we need in our diet and according to how much of the mineral is found in the body. The two categories of minerals in our diet and body are the major minerals and the trace minerals (Table 2).

TABLE 2 Overview of Minerals

• Fat-soluble vitamins Vitamins that are not soluble in water but soluble in fat. These include vitamins A, D, E, and K.
• Water-soluble vitamins Vitamins that are soluble in water. These include vitamin C and the B-vitamins.
• Major minerals Minerals we need to consume in amounts of at least 100 mg per day and of which the total amount in our body is at least 5 g (5,000 mg).
• Trace minerals Minerals we need to consume in amounts less than 100 mg per day and of which the total amount in our body is less than 5 g (5,000 mg).