Ch 1: An Overview of Nutrition

• nutrition: the science of the nutrients in foods and their actions within the body. A broader definition includes the
• study of human behaviors related to food and eating.
• foods: products derived from plants or animals that can be taken into the body to yield energy and nutrients for the
• maintenance of life and the growth and repair of tissues.
• chronic diseases: diseases characterized by slow progression and long duration. Examples include heart disease, diabetes, and some cancers.
• diet: the foods and beverages a person eats and drinks.

• Preferences: taste eg. preference for sweetness of sugar and the savoriness of salt. Research suggests that genetics may influence taste perceptions and therefore food likes and dislikes.
• Habit: out of habit, don't have to make decisions.
• Ethnic heritage and regional cuisines: prefer food they grew up eating
• Social interactions: People also tend to eat the kinds of foods eaten by those in their social circles.
• Marketing: food industry. Brand loyalty, convenience
• Availability, convenience and economy: People often eat foods that are accessible, quick and easy to prepare, and within their financial means.
• Positive and negative associations: People tend to like particular foods associated with happy occasions—such as hot dogs at ball games or cake and ice cream at bday parties.
• By the same token, people can develop aversions to and dislike foods that they ate when they felt sick or that they were forced to eat in negative situations
• Emotions: May eat in response to a variety of emotional stimuli eg boredom or depression.
• Values: religious, political, environmental
• Body weight and health: Such decisions can be beneficial when based on nutrition science, but decisions based on fads or carried to extremes undermine good health.
• Nutrition: many consumers make food choices they believe are nutritious and healthy.

• whole foods: fresh foods such as vegetables, grains, legumes, meats, and milk that are unprocessed or minimally processed.
• processed foods: foods that have been intentionally changed by the addition of substances, or a method of cooking, preserving, milling, or such.
• ultra-processed foods: foods that have been made from substances that are typically used in food preparation, but not consumed as foods by themselves (such as oils, fats, flours, refined starches, and sugars) that undergo further processing by adding a little, if any, minimally processed foods, salt and other preservatives, and additives such as flavors and colors.

• Six classes of nutrients: water, carbohydrates (including fibres), lipids, proteins, vitamins and some minerals
• Substances the body uses for the growth, maintenance and repair of its tissues.
• Foods contain other compounds as well. Some are beneficial, some are neutral, and a few are harmful eg. phytochemicals, pigments, additives, alcohols, and others.

• A chemical analysis of your body would show that it is made of materials similar to those found in foods.
• The human body is made of compounds similar to those found in foods—mostly water (60 percent) and some fat (18 to 21 percent for young men, 23 to 26 percent for young women), with carbohydrate, protein, vitamins, minerals, and other minor constituents making up the remainder.

• energy: the capacity to do work. The energy in food is chemical energy. The body can convert this chemical energy to mechanical, electrical, or heat energy.
• nutrients: chemical substances obtained from food and used in the body to provide energy, structural materials, and regulating agents to support growth, maintenance, and repair of the body’s tissues. Nutrients may also reduce the risks of some diseases.
• phytochemicals (FIE-toe-KEM-ih-cals): nonnutrient compounds found in plants. Some phytochemicals have biological activity in the body.
• phyto= plant

• The simplest of the nutrients are the minerals. Each mineral is a chemical element. Its identity never changes.
• The next simplest nutrient is water, a compound made of two elements—hydrogen and oxygen.
• Minerals and water are inorganic nutrients—which means they do not contain carbon.
• The other four classes of nutrients (carbohydrates, lipids, proteins, and vitamins) are more complex. In addition to hydrogen and oxygen, they all contain carbon, an element found in all living things; they are therefore called organic compounds.

• inorganic: not containing carbon or pertaining to living organisms. The two classes of nutrients that are inorganic are minerals and water.
• organic: in chemistry, substances or molecules containing carbon-carbon bonds or carbon-hydrogen bonds that are characteristic of living organisms. The four classes of nutrients that are organic are carbohydrates, lipids (fats),
• proteins, and vitamins.
• essential nutrients: nutrients a person must obtain from food because the body cannot make them for itself in sufficient quantity to meet physiological needs; also called indispensable nutrients. About 40 nutrients are currently known to be essential for human beings.

• the nutrients that break down to yield energy the body can use: carbohydrate, fat and protein.
• In contrast to these energy-yielding nutrients, vitamins, minerals, and water do not yield energy in the human body.
• Carbohydrate, fat, and protein are sometimes called macronutrients because the body requires them in relatively large amounts (many grams daily)
• In contrast, vitamins and minerals are micronutrients, required only in small amounts (milligrams or micrograms daily)

• The energy released from carbohydrate, fat, and protein can be measured in calories—tiny units of energy.
• To ease calculations, energy is expressed in 1000-calorie metric units known as kilocalories (shortened to kcalories but commonly called "calories")
• When you read in popular books or magazines that an apple provides “100 calories,” it actually means 100 kcalories.

• Energy from foods: The amount of energy a food provides depends on how much carbohydrate, fat, and protein it contains. When completely broken down in
• the body, a gram of carbohydrate yields about 4 kcalories of energy; a gram of protein also yields 4 kcalories; and a gram of fat yields 9 kcalories.
• Because fat provides more energy per gram, it has a greater energy density than either carbohydrate or protein.
• Foods with a high energy density contribute to weight gain, whereas those with a low energy density help with weight loss.

One other substance contributes energy—alcohol. Alcohol, however, is not considered a nutrient. Unlike the nutrients, alcohol does not sustain life. In fact, it interferes with the growth, maintenance, and repair of the body.

energy density: a measure of the energy a food provides relative to the weight of the food (kcalories per gram).

• The international unit for measuring food energy is the joule—the amount of energy
• expended when 1 kilogram is moved 1 meter by a force of 1 newton.
• The joule is thus a measure of work energy, whereas the kcalorie is a measure of heat energy.
• To convert energy measures from kcalories to kilojoules, multiply by 4.2; to convert kilojoules to kcalories, multiply by 0.24.

• To calculate the energy available from a food, multiply the number of grams of carbohydrate, protein, and fat by 4, 4, and 9, respectively.
• From this information, you can calculate the percentage of kcalories each of the energy nutrients contributes to the total.
• Dietary recommendations that urge people to limit fat intake to 20 to 35 percent of kcalories refer to the day’s total energy intake, not to individual foods

When the body uses carbohydrate, fat, or protein to fuel its activities, the bonds between the nutrient’s atoms break. As the bonds break, they release energy. Some of this energy is released as heat, but some is used to send electrical impulses through the brain and nerves, to synthesize body compounds, and to move muscles.

If the body does not use these nutrients to fuel its current activities, it converts them into storage compounds (such as body fat), to be used between meals and overnight when fresh energy supplies run low.

Other roles of energy-yielding nutrients: In addition to providing energy, carbohydrates, fats, and proteins provide the raw materials for building the body’s tissues and regulating its many activities.

• Organic but do not provide energy.
• Instead, they facilitate the release of energy from carbohydrate, fat, and protein and participate in numerous other activities throughout the body.

• Each of the 13 vitamins has its own special roles to play.* One vitamin
• enables the eyes to see in dim light, another helps protect the lungs from air pollution, and still another helps make the sex hormones—among other things.
• Vitamins can function only if they are intact, but because they are complex organic molecules, they are vulnerable to destruction by heat, light, and chemical agents. This is why the body handles them carefully, and why nutrition-wise cooks do, too. The strategies of cooking vegetables at moderate temperatures for short times and using small amounts of water help preserve the vitamins.

• In the body, some minerals are put together in orderly arrays in such structures as bones and teeth. Minerals are also found in the fluids of the body, which influences fluid balance and distribution. Whatever their roles, minerals do not yield energy.
• Only 16 minerals are known to be essential in human nutrition.** Others are being studied to determine whether they play significant roles in the human body.
• Because minerals are inorganic, they are indestructible and need not be handled with the special care that vitamins require. Minerals can, however, be bound by substances that interfere with the body’s ability to absorb them. They can also be lost during food processing or during cooking when they leach into water that is discarded.

Water provides the environment in which nearly all the body’s activities take place. It participates in many metabolic reactions and supplies the medium for transporting vital materials to cells and carrying waste products away from them.