Chapter 7.pdf

The Basics Nutrition can be defined as the science of the action of food, beverages, and their components in biological systems. A nutrient is a compound that provides a needed function in the body. Nutrients can be further classified based on the amount needed in the body. Macronutrients are the nu...

The Basics Nutrition can be defined as the science of the action of food, beverages, and their components in biological systems. A nutrient is a compound that provides a needed function in the body. Nutrients can be further classified based on the amount needed in the body. Macronutrients are the nutrients the body needs in larger amounts. Micronutrients are also important nutrients, but ones the body needs in smaller amounts. Macronutrients Micronutrients Carbohydrate Vitamins Protein Minerals Lipids Water Macronutrients Carbohydrates The word carbohydrate literally means “hydrated carbon,” or carbon with water. Thus, it is no surprise that carbohydrates are made up of carbon, hydrogen, and oxygen. Sucrose (table sugar) is an example of a commonly consumed carbohydrate. Some dietary examples of carbohydrates are whole-wheat bread, oatmeal, rice, sugary snacks/drinks, and pasta. The Basics | 150 Proteins Like carbohydrates, proteins are comprised of carbon, hydrogen, and oxygen, but they also contain nitrogen. Several dietary sources of proteins include nuts, beans/legumes, skim milk, egg whites, and meat. Lipids Lipids consist of fatty acids, triglycerides, phospholipids, and sterols (cholesterol). Lipids are also composed of carbon, hydrogen, and oxygen. Some dietary sources of lipids include, oils, butter, and egg yolks. Water Water is made up of hydrogen and oxygen and is the only macronutrient that provides no energy. Micronutrients Vitamins These compounds are essential for normal physiologic processes in the body. Minerals Minerals are the elements (think periodic table) that are essential for normal physiologic processes in the body. 151 | The Basics Carbohydrates Carbohydrates have become, surprisingly, quite controversial. However, it is important to understand that carbohydrates are a diverse group of compounds that have a multitude of effects on bodily functions. Thus, trying to make blanket statements about carbohydrates is not a good idea. Carbohydrates provide energy for the body as well as fiber for digestive health and blood sugar regulation. Many natural carbohydrates such as fruits, vegetables and whole grains provide essential vitamins and minerals. Carbohydrates can be broken into 2 categories: Simple carbohydrates: found naturally in fruits and milk and are added to candy and sweetened beverages. Simple carbohydrates provide quick energy. Complex carbohydrates: found in grains and legumes provide sustained energy. High-Fructose Corn Syrup Food manufacturers are always searching for cheaper ways to produce their products. One extremely popular method for reducing costs is the use of high-fructose corn syrup as an alternative to sucrose. High-fructose corn syrup is approximately 50% glucose and 50% fructose, which is the same as sucrose. Nevertheless, because increased consumption of high-fructose corn syrup has coincided with increased obesity in the United States, a lot of controversy surrounds its use. The New York Times article linked below discusses the growing Carbohydrates | 152 popularity of sugar compared to high fructose corn syrup: “Sugar is Back on Food Labels, This Time as a Selling Point” Fiber The simplest definition of fiber is indigestible matter. Indigestible means that it survives digestion in the small intestine and reaches the large intestine. There are the three major fiber classifications: 1. Dietary fiber This type of fiber contains both nondigestible carbohydrates and lignin and is always intrinsic and intact in plants. 2. Functional fiber This type of fiber contains nondigestible carbohydrates only and can be isolated, extracted, or synthesized. Functional fiber can be from plants or animals and produces beneficial physiological effects in humans. 3. Total Fiber Fiber that contains both dietary fiber and functional fiber. 153 | Carbohydrates Proteins Protein is another major macronutrient that, like carbohydrates, consists of small repeating units. But instead of sugars, proteins are made up of amino acids. Proteins can be classified as either complete or incomplete. Complete proteins provide adequate amounts of all nine essential amino acids. Animal proteins, such as meat, fish, milk, and eggs, are good examples of complete proteins. Incomplete proteins do not contain adequate amounts of one or more of the essential amino acids. For example, if a protein does not provide enough of the essential amino acid leucine it would be considered incomplete. Leucine would be referred to as the limiting amino acid because there is not enough of it for the protein to be complete. Most plant foods are incomplete proteins, with a few exceptions, such as soy. The table below shows the limiting amino acids in some plant foods. Self Magazine’s Nutrition Data website is a useful resource for determining protein quality and identifying complementary proteins. To use the site, go to www.nutritiondata.com, type the name of the food you want information on in the search bar and hit Enter. When you have selected your food from the list of possibilities, you will be given information about this food. Included in this information is the Protein Quality section. This will give you an amino acid score and a figure that illustrates which amino acid(s) is limiting. If your food is an incomplete protein, you can click “Find foods with a complementary profile.” This will take you to a list of dietary choices that will provide complementary proteins for your food. Proteins | 154 Fats (Lipids) Fats (lipids) are the most concentrated source of energy at 9 calories per gram. Fats provide long term stored energy, insulation, cushion and help the body absorb fat-soluble vitamins. Depending on the fatty acid structure a lipid may be monounsaturated, polyunsaturated, or saturated. Linoleic acid (omega 6) and alpha-linoleic acid (omega 3) are examples of polyunsaturated fats and are essential components of a healthy diet. These healthy fats have an interactive roll in cell metabolism as well as overall vascular health which reduces risk of certain types of heart disease. Trans-Fats When unsaturated fats go through a process of hydrogenation some fatty acids are changed to trans-fats. This hydrogenation process makes liquid fats (such as oils) solid at room temperature and resistant to spoilage. Many food manufacturers used hydrogenated oils in processed foods to give these foods a longer shelf-life. However, trans-fats have a negative impact on health by raising levels of bad cholesterol (LDL) and lowering good cholesterol (HDL). Trans-fats are associated with increased risk of heart disease, stroke and type-2 diabetes. Cholesterol Cholesterol is a fat-like (lipid-like) substance that your body uses as a building block to produce hormones, vitamin D, and digestive 155 | Fats (Lipids) juices that help you break down fats in your diet. HDL (high-density lipoprotein, or “good” cholesterol) and LDL (low-density lipoprotein, or “bad” cholesterol) are two types of lipoproteins that carry cholesterol to and from the body’s cells in the blood.The body needs some cholesterol to function, but when levels get too high, fatty deposits can accumulate in blood vessels, which causes them to narrow. This narrowing of the blood passageways by these lipids can lead to heart attacks, coronary artery disease, strokes, or other vascular diseases. Fats (Lipids) | 156 Vitamins Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. You get most of your vitamins through your diet, although some can be formed from the precursors absorbed during digestion. For example, the body synthesizes vitamin A from the β-carotene in orange vegetables like carrots and sweet potatoes. Vitamins are either fat-soluble or water-soluble. Fat-soluble vitamins A, D, E, and K, are absorbed through the intestinal tract with lipids. Vitamin D is also synthesized in the skin through exposure to sunlight. Because they are carried in lipids, fat-soluble vitamins can accumulate in the lipids stored in the body. If excess vitamins are retained in the lipid stores in the body, hypervitaminosis can result. Water-soluble vitamins, including the eight B vitamins and vitamin C, are absorbed with water in the gastrointestinal tract. These vitamins move easily through bodily fluids, which are water based, so they are not stored in the body. Excess water-soluble vitamins are excreted in the urine. Therefore, hypervitaminosis of water-soluble vitamins rarely occurs, except with an excess of vitamin supplements. 157 | Vitamins Minerals Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requires in moderate quantities: potassium, sodium, calcium, phosphorus, magnesium, and chloride. The most common minerals in the body are calcium and phosphorous, both of which are stored in the skeleton and necessary for the hardening of bones. Most minerals are ionized, and their ionic forms are used in physiological processes throughout the body. Sodium and chloride ions are electrolytes in the blood and extracellular tissues, and iron ions are critical to the formation of hemoglobin. There are additional trace minerals that are still important to the body’s functions, but their required quantities are much lower. Like vitamins, minerals can be consumed in toxic quantities (although it is rare). A healthy diet includes most of the minerals your body requires, so supplements and processed foods can add potentially toxic levels of minerals. The Major Minerals table provides a summary of minerals and their function in the body. Minerals | 158 Calories (Food Energy) Food energy is measured in kilocalories (kcals), commonly referred to as calories. Although technically incorrect, this terminology is so familiar that it will be used throughout this course. A kilocalorie is the amount of energy needed to raise 1 kilogram of water 1 degree Celsius. The number of kilocalories per gram for each nutrient is shown below: Nutrient Energy (kcal/g) Carbohydrate 4 Protein 4 Lipids 9 Water 0 Vitamins 0 Minerals 0 As the table above illustrates, only carbohydrates, protein, and lipids provide energy. However, there is another dietary energy source that is not a nutrient—alcohol. To emphasize, alcohol is not a nutrient, but it does provide 7 kilocalories of energy per gram. Knowing the number of calories in each nutrient allows a person to calculate/estimate the amount of calories contained in any food consumed. My Plate On average, a person needs 1500 to 2000 calories per day to sustain 159 | Calories (Food Energy) (or carry out) daily activities. The total number of calories needed by one person is dependent on their body mass, age, height, gender, activity level, and the amount of exercise per day. If exercise is regular part of one’s day, more calories are required. As a rule, people underestimate the number of calories ingested and overestimate the amount they burn through exercise. This can lead to ingestion of too many calories per day. The accumulation of an extra 3500 calories adds one pound of weight. If an excess of 200 calories per day is ingested, one extra pound of body weight will be gained every 18 days. At that rate, an extra 20 pounds can be gained over the course of a year. Of course, this increase in calories could be offset by increased exercise. Running or jogging one mile burns almost 100 calories. The type of food ingested also affects the body’s metabolic rate. Processing of carbohydrates requires less energy than processing of proteins. In fact, the breakdown of carbohydrates requires the least amount of energy, whereas the processing of proteins demands the most energy. In general, the amount of calories ingested and the amount of calories burned determines the overall weight. To lose weight, the number of calories burned per day must exceed the number ingested. Calories are in almost everything you ingest, so when considering calorie intake, beverages must also be considered. To help provide guidelines regarding the types and quantities of food that should be eaten every day, the USDA has updated their food guidelines from MyPyramid to MyPlate. They have put the recommended elements of a healthy meal into the context of a place setting of food. MyPlate categorizes food into the standard six food groups: fruits, vegetables, grains, protein foods, dairy, and oils. The accompanying website gives clear recommendations regarding quantity and type of each food that you should consume each day, as well as identifying which foods belong in each category. The accompanying graphic (Figure) gives a clear visual with general recommendations for a healthy and balanced meal. The guidelines Calories (Food Energy) | 160 recommend to “Make half your plate fruits and vegetables.” The other half is grains and protein, with a slightly higher quantity of grains than protein. Dairy products are represented by a drink, but the quantity can be applied to other dairy products as well. MyPlate The U.S. Department of Agriculture developed food guidelines called MyPlate to help demonstrate how to maintain a healthy lifestyle. Myplate.gov