Chapter 8

Nutritional Requirements: Components of a Healthy Diet

Essential nutrients = substances the body must get from food because it cannot manufacture them at all or fast enough to meet its needs Proteins Carbohydrates Fats Vitamins Minerals Water

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Energy from Food

Three classes of essential nutrients supply energy. Which ones?

Kilocalorie = a measure of energy content in food; the amount of heat it takes to raise the temperature of 1 liter of water 1°C; commonly referred to as “calorie”

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Sources of Energy in the Diet

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Proteins—The Basis of Body Structure Protein = a compound made of amino

acids that contains carbon, hydrogen, oxygen, and nitrogen

Of twenty common amino acids in foods, nine are essential

Proteins form key parts of the body’s main structural components—muscles and bones—and of blood, enzymes, cell membranes, and some hormones

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Fats—Essential in Small Amounts Fats supply energy, insulate the

body, support and cushion organs, absorb fat-soluble vitamins, add flavor and texture to foods

Essential fats are key regulators of body process such as the maintenance of blood pressure and the progress of a healthy pregnancy

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Types and Sources of Fats Saturated fat = a fat with no carbon-carbon

double bonds; usually solid at room temperature Found primarily in animal foods and palm and

coconut oils Monounsaturated fat = a fat with one carbon-

carbon double bond; usually liquid at room temperature Found in certain vegetables, nuts, and

vegetable oils Polyunsaturated fat = a fat with two or more

carbon-carbon double bonds; usually liquid at room temperature Found in certain vegetables, nuts, and

vegetable oils and in fatty fishChapter 8 7

Fats and Health

Fats also affect triglyceride levels, inflammation, heart rhythm, blood pressure, and cancer risk

Best choices = monounsaturated fats and polyunsaturated omega-3 fats

Limit intake of saturated and trans fats

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Fats and Health Fats affect blood cholesterol levels

Low-density lipoprotein (LDL) = “bad” cholesterol

High-density lipoprotein (HDL) = “good” cholesterol

Saturated and trans fats raise levels of LDL; trans fats also lower levels of HDL

Unsaturated fats lower levels of LDL

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Carbohydrates—An Ideal Source of Energy

The primary function of dietary carbohydrate is to supply energy to body cells.

Some cells, such as those in the brain, nervous system, and blood, use only carbohydrates for fuel

During high-intensity exercise, muscles get most of their energy from carbohydrates

During digestion, carbohydrates are broken into single sugar molecules such as glucose for absorption; the liver and muscles take up glucose and store it in the form of glycogen

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Simple and Complex Carbohydrates

Simple carbohydrates contain one or two sugar units in each molecule Found naturally in fruits and milk and added to

many other foods Include sucrose, fructose, maltose, and lactose

Complex carbohydrates consist of chains of many sugar molecules Found in plants, especially grains, legumes,

and tubers Include starches and most types of dietary fiber

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Whole Grains

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Before they are processed, all grains are whole grains consisting of an inner layer of germ, a middle layer called the endosperm, and an outer layer of bran

During processing, the germ and bran are often removed, leaving just the starchy endosperm

Refined carbohydrates usually retain all the calories of a whole grain but lose many of the nutrients

Refined Carbohydrates Versus Whole Grains

Whole grains are higher than refined carbohydrates in fiber, vitamins, minerals, and other beneficial compounds

Whole grains take longer to digest Make people feel full sooner Cause a slower rise in glucose levels

Choose foods that have a whole grain as the first item on the ingredient list on the food label Whole wheat, whole rye, whole oats, oatmeal,

whole-grain corn, brown rice, popcorn, barley, etc.

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Reading a Food Label

1. Serving Size

The first place to start when you look at the Nutrition Facts label

Serving sizes are standardized to make it easier to compare similar foods;

They are provided in familiar units, such as cups or pieces, followed by the metric amount, e.g., the number of grams.

The size of the serving on the food package influences the number of calories and all the nutrient amounts listed on the top part of the label.

Pay attention to the serving size, especially how many servings there are in the food package. Then ask yourself, "How many servings am I consuming"? (e.g., 1/2 serving, 1 serving, or more)

In the sample label, one serving of macaroni and cheese equals one cup. If you ate the whole package, you would eat two cups. That doubles the calories and other nutrient numbers, including the %Daily Values as shown in the sample label.

2. Calories (and calories from fat)

Calories provide a measure of energy The calorie section of the label can help

you manage your weight. Only about 30% of your calories should

come from fat. Remember: the number of servings

you consume determines the number of calories you actually eat (your portion amount).

A guide: 40 Calories is low, 100 Calories is moderate and 400 Calories or more is high

3. The nutrientsLimit These Nutrients Get Enough of These

Eating too much fat, saturated fat, trans fat, cholesterol, or sodium may increase your risk of certain chronic diseases, like heart disease, some cancers, or high blood pressure.

Eating enough of these nutrients can improve your health and help reduce the risk of some diseases and conditions. Remember: You can use the Nutrition Facts label not only to

help limit those nutrients you want to cut back on but also to increase those nutrients you need to consume in greater amounts.

5. Understanding the Footnote on the Bottom of the Nutrition Facts Label

This statement must be on all food labels.

6. The Percent Daily Value (%DV)

5%DV or less is low and 20%DV or more is high

Plain vs Fruit Yogurt

Glycemic Index Consumption of carbohydrates causes insulin and

glucose levels in the blood to rise and fall Glycemic index = a measure of how the ingestion

of a particular food affects blood glucose levels Foods with a high glycemic index cause quick and

dramatic changes in glucose levels Diets rich in high glycemic index foods are linked to

increased risk of diabetes and heart disease High glycemic: Bread, Pasta, Rice, Baked goods Low glycemic: Fruits, Vegetables, Whole grains

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Acceptable Macronutrient Distribution Ranges: Summary Protein = 10–35% of total daily

calories Fat = 20–35% of total daily calories Carbohydrate = 45–65% of total

daily calories

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Fiber—A Closer Look

Dietary fiber = nondigestible carbohydrates and lignin that are present naturally in plants

Functional fiber = nondigestible carbohydrates isolated from natural sources or synthesized in a lab and added to a food or supplement

Total fiber = dietary fiber + functional fiber

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Types of Fiber

Soluble (viscous) fiber = fiber that dissolves in water or is broken down by bacteria in the large intestine Slows the body’s absorption of glucose Binds cholesterol-containing compounds

Insoluble fiber = fiber that doesn’t dissolve in water Makes feces bulkier and softer Helps prevent constipation, hemorrhoids, and

diverticulitis

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Sources of Fiber

All plant foods contain fiber, but processing can remove it

Good sources of fiber: Fruits (especially whole, unpeeled fruits) Vegetables Legumes Oats (especially oat bran) Whole grains and wheat bran Psyllium (found in some cereals and laxatives)

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Vitamins—Organic Micronutrients

Vitamins = organic (carbon-containing) substances needed in small amounts to help promote and regulate chemical reactions and processes in body cells.

Four vitamins are fat-soluble (A, D, E, and K) Nine vitamins are water-soluble (C and the

eight B-complex vitamins: thiamin, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, biotin, and pantothenic acid)

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Vitamins

Vitamins are abundant in fruits, vegetables, and grains; they are also added to some processed foods

If you consume too much or too little of a particular vitamin, characteristic symptoms of excess or deficiency can develop

Vitamins commonly lacking in the American diet: Vitamin A Vitamin C Vitamin B-6 Vitamin E

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Minerals—Inorganic Micronutrients

Minerals = inorganic (non-carbon-containing) compounds needed in small amounts for regulation, growth, and maintenance of body tissues and functions

There are about 17 essential minerals: Major minerals (those that the body needs in

amounts exceeding 100 mg per day) include calcium, phosphorus, magnesium, sodium, potassium, and chloride

Essential trace minerals include copper, fluoride, iodide, iron, selenium, and zinc

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Minerals

If you consume too much or too little of a particular mineral, characteristic symptoms of excess or deficiency can develop

Minerals commonly lacking in the American diet: Iron = low intake can cause anemia Calcium = low intake linked to osteoporosis Potassium = low intake linked to elevated

blood pressure and bone mineral loss

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Water—A Vital Component

Human body is composed of about 60% water; you can live only a few days without water

Foods and fluids you consume provide 80–90% of your daily water intake

Adequate intake to maintain hydration: Women need to drink about 9 cups of fluid per day Men need to drink about 13 cups of fluid per day

Drink in response to thirst; consume additional fluids for heavy exercise

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Other Substances in Food: Antioxidants

Antioxidant = a substance that protects against the breakdown of body constituents by free radicals; actions include binding oxygen, donating electrons to free radicals, and repairing damage to molecules Free radical = a chemically unstable, electron-

seeking compound that can damage cell membranes and mutate genes in its search for electrons

Many fruits and vegetables are rich in antioxidants such as vitamin C, vitamin E, selenium, and carotenoids

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Should You Take Supplements?

The Food and Nutrition Board recommends supplements only for certain groups: Folic acid for women capable of becoming

pregnant (400 µg/day) Vitamin B-12 for people over age 50 (2.4 mg/day)

Other possible situations for supplements: Vitamin C for smokers Iron for menstruating women Vitamin K for newborns People with certain special health concerns

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Leading Sources of Calories in the American Diet 1. Regular soft drinks (7.1% of total calories) 2. Cake, sweet rolls, doughnuts, pastries (3.6%) 3. Hamburgers, cheeseburgers, meat loaf (3.1%) 4. Pizza (3.1%) 5. Potato chips, corn chips, popcorn (2.9%) 6. Rice (2.7%) 7. Rolls, buns, English muffins, bagels (2.7%) 8. Cheese or cheese spread (2.6%) 9. Beer (2.6%)10. French fries, fried potatoes (2.2%)Source: Block, G. 2004. Foods contributing to energy intake in the U.S.: Data from NHANES III and NHANES 1999–2000. Journal of Food Composition and Analysis 17: 439–447.

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Alternative Food Plans: Healthy Eating Pyramid

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Alternative Food Plans: Canada’s Food Guide

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Dietary Challenges for Special Population Groups: Athletes

Energy intake—adequate calories and nutrients Carbohydrates—60 to 65% of total daily

calories for most athletes, up to 70% for endurance athletes

Protein (grams per day per kilogram of body weight) Endurance athletes: 1.2 to 1.4 grams Heavy strength training: 1.6 to 1.7 grams

Fluids—remain hydrated 14 to 22 oz of fluid two hours before strenuous event 6 to 12 oz every 15–20 minutes during exercise Replace fluids after event (check body weight)

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A Personal Plan: Applying Nutritional Principles Assess your current diet Set goals for change Try additions and substitutions to

bring your current diet closer to your goals

Plan ahead for challenging situationsMake smart choices about nutrition!

See the following recommendations.

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What Type of Food Should People Choose?

The type of food that people eat is just as important as the amount.

Eat at least one dark green and one orange vegetable each day.

Have vegetables and fruit more often than juice. Make at least half of your grain products whole

grain each day. Drink skim, 1% or 2% milk each day. Have meat alternatives such as beans, lentils and

tofu often. Eat at least two Food Guide Servings of fish each

week. Include a small amount of unsaturated fat each

day. Satisfy your thirst with water.

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Lowering fat

It is best to reduce the total amount of fat in your diet and reduce the amount of saturated and trans fats you consume.

Higher fat foods are often higher in saturated and trans fats. These kinds of fats put people at higher risk of cardiovascular disease.

Saturated fats are found in fatty meats, higher fat milk products, butter, lard, shortening, hard margarines and tropical oils such as coconut and palm oil.

Trans fats are found in many deep-fried foods, fast foods, salty snacks and baked goods made with shortening or partially hydrogenated vegetable oils.

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Lowering salt

Most people get more sodium than they need, especially if they eat packaged, processed foods and meals made outside of the home.

Some of the foods that can be high in sodium include snack foods, such as crackers, nachos, potato chips and pretzels, cheese, gravies and sauces, processed luncheon meats, canned or dried soups and frozen meals.

People should compare the Nutrition Facts table on similar products and choose the one that has a lower number for the % Daily Value of sodium.

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Lowering sugar

Baked goods and desserts, such as cakes, candies, chocolate, cookies, doughnuts, ice cream, muffins, pastries and pies, and sweetened cold and hot beverages, such as energy drinks, fruit flavoured drinks, soft drinks, sports drinks, hot chocolate and specialty coffees, can be high in sugar and should be limited.

When cooking, try roasting, grilling, baking, stir-frying, steaming or poaching - all methods that require little or no added fat. For tips on preparing foods with little or no added fat, sugar or salt.

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Remember

Think before you eat! Move! (energy balance) Make a plan for yourself – it is your

body, your health! Enjoy your life but do it in a smart

way!

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