An Introduction to Nutrition

• Introduction
• Recommended Dietary Allowances
• What counts as a serving?
• Dietary Fiber
• Recommended Daily Allowance of Fiber
• Side Effects of Fiber
• Vegetarian Diets
• Nutrition for Women
• Fast Food Facts
• Supplements
• Questions to Ask Your Doctor

Introduction

An individual's food choices depend on energy needs, nutrient needs and enjoyment. Family, friends and personal beliefs, including cultural and environmental considerations, also play a major role in people's food selection.

Many genetic, environmental, behavioral and cultural factors can affect a person's health. Understanding family history of disease or risk factors, such as body weight and fat distribution, blood pressure and blood cholesterol, can help people make more informed decisions about how to improve health. Making good food choices is among the most pleasurable and effective ways of improving health.

Healthful diets help children grow, develop and perform well in school. A healthy diet allows adults to work productively and feel their best. Good food choices also can help to prevent chronic diseases, such as heart disease, certain cancers, diabetes, stroke and osteoporosis, that are leading causes of death and disability among Americans. A proper diet can also reduce major risk factors for chronic diseases, such as obesity, high blood pressure and high blood cholesterol.

People require energy and certain essential nutrients. These nutrients are essential because the body cannot make these nutrients on its own and must obtain them from food. Essential nutrients include vitamins, minerals, certain amino acids and certain fatty acids. Foods also contain fiber and other components that are important for health. Each of these food components has a specific function in the body and they are all required for overall health. For example, people need calcium for strong bones, for example, but many other nutrients also take part in building and maintaining bones.

The carbohydrates, fats and proteins in food supply energy, which is measured in calories. Carbohydrates and proteins provide 4 calories per gram. Fat contributes more than twice as much -- 9 calories per gram -- and foods that are high in fat are also high in calories. Alcohol is also high in energy and supplies 7 calories per gram.

Energy needs vary by age. For example, older adults need less food than younger and more active individuals. People who are inactive or trying to lose weight may eat small amounts of food and have difficulty meeting their nutrient needs in a satisfying diet. Increasing the energy spent in daily activities can help people reach their health and weight goals while eating a more nutritious and satisfying diet.

Healthful diets contain the amounts of essential nutrients and energy needed to prevent nutritional deficiencies and excesses. Healthful diets also provide the right balance of carbohydrate, fat and protein to reduce risks for chronic diseases, and these diets can be achieved through a variety of foods that are available, affordable and enjoyable.

Back to top

Recommended Dietary Allowances

Recommended Dietary Allowances (RDAs) Average daily nutrient level that is sufficient to meet the nutrient requirements of nearly all individuals in a life stage and gender group.

Food Labels

The Nutrition Facts Label is designed to help you select foods that will meet the Dietary Guidelines for Americans, published jointly by the U.S. Departments of Agriculture and Health and Human Services. Most processed foods now carry nutrition information. However, foods such as coffee and tea (which contain no significant amounts of nutrients), ready-to-eat foods such as deli and bakery items, and restaurant food are not required to carry nutrition labels. Labels are also voluntary for many raw foods, but grocers can supply this information for the raw fruits, vegetables, fish, meat and poultry that are consumed most frequently. Use the food label to choose healthful foods each day.

Food Guide Pyramid

To obtain the nutrients and other substances needed for good health, vary the foods you eat. Foods contain combinations of nutrients and other healthful substances. No single food can supply all nutrients in the amounts you need. For example, oranges provide vitamin C but no vitamin B12. Cheese provides vitamin B12 but no vitamin C. To make sure you eat all of the nutrients and other substances needed for good health, choose the recommended number of daily servings from each of the five different food groups displayed in the Food Guide Pyramid.


(click graphic for larger image)

Americans do choose a wide variety of foods. However, people often choose higher or lower amounts from some food groups than recommended in the Food Guide Pyramid. The pyramid shows that foods from the grain group, along with vegetables and fruits, are the basis of healthful diets. Enjoy meals that have whole grains, brown rice, pasta, potatoes or bread at the center of the plate, accompanied by vegetables and fruit, and lean and low-fat foods from the other groups such as cheese, eggs and meats. Limit fats and sugars added in food preparation. Compare the recommended servings in box 1 with what you usually eat.

The Food Guide Pyramid shows the recommended balance among food groups in a daily eating pattern. Most of the daily servings of food should be selected from the food groups that are the largest in the picture and closest to the base of the pyramid.

• Choose most of your calories from foods in the grain group (6-11 servings), the vegetable group (3-5 servings) and the fruit group (2-4 servings).
• Eat moderate amounts of foods from the dairy group (2-3 servings) and the meat and beans group (2-3 servings).
• Choose fewer foods high in fat and sugars (consume sparingly).

Note: A range of servings is given for each food group. The smaller number is for people who consume about 1,600 calories per day. The larger number is for those who consume about 2,800 calories per day.

Back to top

What counts as a serving?

See below for suggested serving sizes in the Food Guide Pyramid food groups. Notice that some of the serving sizes are smaller than what you might usually eat. For example, many people eat a cup or more of pasta in a meal, which is equal to two or more servings. So, it is easy to eat the number of servings recommended.

Bread, Cereal, Rice and Pasta

• 1 slice of bread
• 1 ounce of ready-to-eat cereal
• 1/2 cup of cooked cereal
• 1/3 cup rice and pasta

Vegetables

• 1 cup of raw leafy vegetables
• 1/2 cup of other vegetables -- cooked or chopped raw
• 3/4 cup of vegetable juice

Fruit

• 1 medium apple, banana, orange
• 1/2 cup of chopped, cooked or canned fruit
• 1/2 cup of fruit juice

Milk, Yogurt and Cheese

• 1 cup of milk or yogurt
• 1-1/2 ounces of natural cheese
• 2 ounces of processed cheese

Meat, Poultry, Fish, Dry Beans, Eggs and Nuts

• 2-3 ounces of cooked lean meat, poultry or fish
• 1/2 cup of cooked dry beans, 1 egg or 2 tablespoons of peanut butter are equivalent to 1 ounce of lean meat

Some foods fit into more than one category. Starchy vegetables such as potatoes, corn, sweet potatoes and taro (poi) can be counted as servings in the grain products group instead of as vegetables. Dry beans, peas and lentils are in the meat group but can be counted as servings of grains instead. These crossover foods can be counted as servings from either one or the other group, but not both.

You can achieve a healthful, nutritious eating pattern with many combinations of foods from the five food groups. Choosing a variety of foods within and across food groups improves dietary patterns because foods within the same group have different combinations of nutrients and other beneficial substances. For example, some vegetables and fruits are good sources of vitamin C or vitamin A, while others are high in folate; still others are good sources of calcium or iron. Choosing a variety of foods within each group also helps to make your meals more interesting from day to day.

Back to top

Dietary Fiber

Dietary fiber (also know as "roughage" or "bulk") is the part of the food that is indigestible. Found only in plant foods, it moves unaltered through the stomach and small intestine and into the colon.

There are two types of dietary fiber: insoluble and soluble. Insoluble fiber doesn't dissolve in water and travels through the small intestines quickly. Wheat bran, whole grain breads and cereals, as well as the skins of many fruits and vegetables, are considered insoluble. Soluble fiber breaks down as it passes through the digestive tract, forming a gel that traps some substances that are beneficial in lowering cholesterol, stabilizing blood sugar and affecting nutrient absorption. Examples of soluble fibers are oats, beans, barley, and many fruits and vegetables.

Fiber has two well-known benefits:

• Prevents and relieves constipation by stimulating movement of your intestinal muscles, increasing stool bulk and making your stools softer and easier to pass.
• Controls weight by creating a feeling of fullness without adding too many calories to the diet.

Dietary fiber also can reduce the risk of many other health conditions including the conditions listed below"

Gastrointestinal disorders. Avoiding constipation reduces the risk of developing hemorrhoids (swollen anal tissues), diverticulosis (pouches that protrude through weak spots in the colon) and irritable bowel syndrome (muscle spasms in the stomach walls).

Elevated cholesterol. Soluble fiber binds with certain digestive acids made from cholesterol in the liver, and then takes the acids away in the stool. In response, your liver draws cholesterol from your blood to make more acids, thus lowering your blood cholesterol.

Diabetes. Soluble fiber slows absorption of blood sugar from the small intestine, making sugar levels easier to control.

Heart Disease. Soluble fiber lowers levels of cholesterol, which plays a role in heart disease.

Colon Cancer. Insoluble fiber minimizes exposure to carcinogens that may be in the stool by diluting them and speeding their transit through the bowel. Additionally, the insoluble fiber reduces bile acids and certain bacterial enzymes that may promote the growth of precancerous polyps (tissue growths that protrude from a membrane such as the intestinal lining) and colon cancer.

Breast Cancer. Prolonged exposure to increased estrogen and progesterone in the body increases cancer risk. Fiber helps speed cancerous substances, that have reached the intestines, out of the body before they can cause serious damage. Women who eat extra fiber rid themselves of their excess estrogen in bowel movements rather than in urine. This is important because estrogen in the urine can be reabsorbed into the blood stream and eventually reach the breasts and other organs vulnerable to hormone-related cancer. Dietary fiber "binds up" estrogen as it enters the small intestine, and may do the same with other cancer-causing agents, preventing them from being absorbed.

Overall, studies have clearly strengthened the belief that fiber not only fights relatively minor intestinal disorders, such as diverticulosis and constipation, but may also help prevent coronary disease and cancer. However, the strongest evidence of a major reduction in risk comes from studies of diets that are rich in high-fiber foods, not just in fiber alone. Such foods, which are low in fat and rich in nutrients, have many health benefits beyond those provided by the fiber itself.

Back to top

Recommended Daily Allowance of Fiber

The Dietary Guidelines for Americans recommends eating foods that have adequate amounts of fiber. The National Cancer Institute and The American Heart Association (AHA) both recommend consuming 20 to 35 grams of fiber per day.

Americans typically consume 10 to 15 grams of fiber per day. Consuming the following recommended servings of a variety of fruits, vegetables, and grains throughout the day should bring the intake within the range recommended by the National Cancer Institute, AHA, and U.S. Department of agriculture.

Food
Fruits (2 to 4 servings per day)
Examples of Serving Size
Apple -- 1 medium
Banana -- 1 medium
Orange -- 1 medium

Vegetables (3 to 5 servings per day) ½ cup cooked or 1 cup raw
Peas
Potatoes (with skin)
Corn
Green beans
Broccoli
Carrots

Grains (6 to 11 servings)
Legumes-1/2 cup cooked
Oatmeal (cooked) -- 1/2 cup
Brown rice -- 1/3 cup
Whole Wheat bread -- 1 slice
100% Bran -- 1/2 cup

Note: fiber needs fluid to be effective so it's important to drink about 64 ounces of water daily.

Back to top

Side Effects of Fiber

It's important to adjust fiber intake gradually over a period of one to two weeks. This will give the stomach and intestines time to adjust to the dietary change. It will also minimize problems such as diarrhea, bloating or gas that can result when too much fiber is consumed. Moderation is particularly important for older people because their bowel function may be sluggish.

It has been feared that very high-fiber diets could, because of fiber's binding abilities, lead to deficiencies of calcium, zinc and other minerals. However, current evidence suggests that moderate fiber intake will not cause nutrient deficiencies.

Fiber supplements (such as Citrucel, FiberCon, GenFiber, Hydrocil and Metamucil) should be used only with a physician's recommendations. Taken properly, these supplements may help with constipation, cholesterol levels or intolerance to high-fiber foods, but their anti-cancer benefit is questionable. Relying solely on fiber supplements is unwise because they don't contain the many essential nutrients found in high-fiber foods.

Back to top

Vegetarian Diets

Some Americans eat vegetarian diets for reasons of culture, belief or health. Most vegetarians eat dairy products and eggs and, overall as a group, these lacto-ovo vegetarians enjoy excellent health. Vegetarian diets are consistent with the Dietary Guidelines and can meet RDA's for nutrients if food are varied and properly proportional. In most American diets, meat, fish, and poultry are major contributors of iron, zinc, and B vitamins, and vegetarians should pay special attention to making sure they get these nutrients. They also must ensure they get adequate amounts of protein, which can be found in sources such as beans and soy products.

Vegans eat only food of plant origin. Because animal products are the only food sources of vitamin B12, vegans must supplement their diets with a source of this vitamin. In addition, vegan diets, particularly in children, should include adequate amounts of vitamin D and calcium, which most Americans obtain from dairy products. Vegan diets may also be low in iron, since iron is best absorbed from meat products. Vegans need to take special to consume other sources of iron rich food (see list below) or check with their physician to discuss iron supplementation.

Back to top

Nutrition for Women

Many women and adolescent girls need to eat more calcium-rich foods to help them maintain healthy bones throughout life. By selecting low-fat or fat-free dairy items and other low-fat calcium sources, they can obtain adequate calcium and prevent excessive fat intake (see list of sources of calcium below).

Good Sources of Calcium*

• Most foods in the dairy group(see dairy group note below)
  • Milk and dishes made with milk, such as potato soup and puddings
  • Cheeses like mozzarella, cheddar, Swiss and parmesan
  • Yogurt
• Canned fish with soft bones such as sardines, anchovies and salmon.
• Leafy greens of the cabbage family, such as kale, mustard greens and turnip tops, and bok choy.
• Tofu, if processed with calcium sulfate. Read the labels.
• Tortillas made from lime-processed corn. Read the labels.

*Note about dairy group -- Some foods in this group are high in fat or cholesterol or both. Choose low-fat and low-cholesterol foods most often.

Young children, teenage girls and women of childbearing age should also eat enough iron-rich foods, such as lean meats and whole-grain or enriched white bread, to keep the body's iron stores at adequate levels (see list of sources of iron below).

Good Sources of Iron*

• Meats -- beef, pork and lamb, especially liver and other organ meats
• Poultry -- chicken, duck and turkey, especially liver and dark meat
• Shellfish such as clams, mussels and oysters; sardines; anchovies; and other fish
• Leafy greens such as cooked collard greens and spinach
• Dried beans and peas, such as soy beans, green peas, lima beans, black beans, black-eyed peas and canned baked beans
• Iron-enriched white bread, pasta, rice and cereals. Read the labels.
• Sunflower seeds and raisins

*Note about meat, poultry and fish: Some foods in these categories are high in fat or cholesterol or both. Choose lean, lower-fat and lower-cholesterol foods most often.

Back to top

Fast Food Facts

Did you know there are more than 300,000 fast food restaurants in the United States? Fast food is convenient, predictable and quick, and it has become common in the busy American lifestyle. But fast food is often high in calories, sodium, fat and cholesterol. This does not mean fast food is always bad. But it does mean you should eat fast food only in moderation as part of a balanced, healthy diet.

See how easily the red-flag items of calories, fat, sodium and cholesterol can add up in a fast food meal:

1. Burger

Quarter-Pound Cheeseburger, Large Fries, medium 21 oz. soda (McDonald's)

This meal:	Recommended daily intake:
1,270 calories	2,000-2,500 calories
54g fat	No more than 70-90 g
95 mg cholesterol	No more than 300 mg
1,580 mg sodium	No more than 1,500-3,000 mg

2. Pizza
Four slices regular crust Sausage and Mushroom Pizza, medium 21 oz.
soda (Domino's)

This meal:	Recommended daily intake:
1,126 calories	2,000-2,500 calories
34 g fat	No more than 70-90 g
78 mg cholesterol	No more than 200 mg
2,032 mg sodium	No more than 1,500-3,000 mg

3. Chicken
Two pieces original recipe Fried Chicken (Breast and Wing), Buttermilk Biscuit, Mashed Potatoes and Gravy, Corn-on-the-Cob, 21 oz. soda (KFC)

This meal:	Recommended daily intake:
1,200 calories	2,000-2,500 calories
52 g fat	No more than 70-90 g
190 mg cholesterol	No more than 200 mg
2,650 mg sodium	No more than 1,500-3,000 mg

4. Tacos
Taco Salad with salsa, medium 21 oz. soda (Taco Bell)

This meal:	Recommended daily intake:
1,060 calories	2,000-2,500 calories
52 g fat	No more than 70-90 g
70 mg cholesterol	No more than 200 mg
2,250mg sodium	No more than 1,500-3,000 mg

Back to top

Supplements

Supplements of vitamins, minerals or fiber also may help to meet nutritional needs. However, supplements do not supply all of the important nutrients present in foods, and they can be harmful if taken regularly in large amounts. Daily vitamin and mineral supplements at or below the Recommended Dietary Allowances are considered safe but are rarely needed by people who eat the variety of foods recommended in the Food Guide Pyramid.

Sometimes supplements are needed to meet specific nutrient requirements. For example, older people and individuals with little exposure to sunlight may need a vitamin D supplement. Women of childbearing age may reduce the risk of certain birth defects by consuming folate-rich foods or taking folic acid supplements. Iron supplements are also recommended for pregnant women.

Back to top

Questions to Ask Your Doctor

• Can cholesterol levels change from day to day depending on your diet?
• What should my cholesterol goal be?
• Can you recommend a dietitian or some other resource to help me obtain information about an appropriate diet?
• Do you recommend any medications to help lower cholesterol levels? If so, what are the side effects?
• How often should cholesterol level be checked?
• What is the best type of exercise and how much is safe but effective? Is there an exercise program you recommend?

Back to top