Our Food Provides Us with Energy- What Else Does It Provide Us With

PPT Nutrition

Developer Notes

Goals

Discuss nutrition

Understand metabolic needs

Concepts & Skills Introduced

Area

Concept

Physiology

Classes of nutrients

Physiology

Diet adequacy

Time Required

One class period

Warm-up Question

What’s in the food we eat?

Presentation

You can use the warm-up question to start the discussion on classes of nutrients.

A good activity is to have the students bring in and analyze food labels.

This reading is a follow-up to the reading on energy needs in the body. Reading

NUTRITION

We already know that our food provides us with energy - what else does it provide us with? Amino acids (which are the building blocks for proteins), vitamins, and minerals are all necessary to body building and maintenance. A healthy diet provides enough energy and other things you need to build and maintain your body.

Everything you eat is made up of some combination of these things:

Nutrient Class / Function
Carbohydrates / Serve as the primary source of energy for biological work. The muscular system and the brain rely almost solely on carbohydrates. There is a limit to how much carbohydrate (in the form of glycogen) you can store in your body. Excess carbohydrates are stored as fat.
Lipids (Fats & oils) / Provide the most energy-rich chemical bonds, but are more difficult to break down. They are considered a secondary source of energy. Fats are easily stored in the body. Stored fat does have several valuable purposes, including cushioning organs, providing insulation, carrying fat-soluble vitamins, and providing an extra store of energy for when you're sick or can't get food.
Proteins / Essential for maintenance, growth and repair of cells. Proteins are made up of long chains of amino acids. There are 20 different amino acids and the body is able to synthesize 11 of these. The remaining 9 must be consumed in your diet. Protein is only used as an energy source in extreme conditions (e.g., starvation, extreme weight training). Excess protein can not be stored in the body, and if you eat more than you need it is converted to lipids and stored as fat.
Water / 40-60% of your body is water. It is necessary to stabilize body temperature, carry nutrients, including water-soluble vitamins, and waste products. It is essential for all cell functions.
Vitamins / Regulate chemical reactions in the body and are needed for tissue synthesis. They are classified as either water or fat-soluble. Not enough or excess of some vitamins can cause illness or even death. Vitamin deficiencies are rare when eating a balanced diet.
Minerals / Regulate body processes and form some structures in the body (e.g., the bones are made predominantly of calcium). Needed for enzyme, hormone and some vitamin functioning. Excess consumption is useless and sometimes toxic to the body. Many minerals are needed in very small amounts, are re-usable, and deficiencies (with the exception of calcium and iron) are rare.

A balanced diet can provide all of these things for you. Current nutrition research recommends that 60% of the calories you consume should come from carbohydrates, only 25% should be fat and 15% protein. This is where most people need to make the changes in their eating habits.

Many people get stressed out at the thought of trying to put together a balanced diet, but it can be pretty easy if you have the right information!

How many calories you can consume in a day without gaining or losing weight depends on your level of activity and your metabolism. Average daily metabolic rates for people who only do light activities are as follows:

Cal

Age expended/day

Males Females

15 - 18 2800 2200

19 - 22 2900 2100

23 - 50 2700 2000

51 - 75 2400 1800

These numbers are considerably higher for a very active person- it can be closer to 5000 Cal/day for males and 3500 Cal/day for females. You’d be surprised, however, just how hard you do have to work to burn those extra calories. For example, running a 26.2 mile marathon only burns about 2800 Calories. That’s not even one pound of fat! (A pound of fat is the equivalent of 3500 Calories). So, if you want to lose weight you’re better off not eating dessert than thinking you’ll burn it off jogging around the block - you’d be jogging a very long time.

Counting calories is a drag. There are easier ways to watch what you eat without getting fanatical about everything that goes in your mouth. The easiest rule of thumb is to have 1-2 servings from the meat group, 2-3 from the dairy group, and 2-4 servings of fruit, 4-6 of vegetables/bean, and 6-11 in the cereal/bread group. (See below for serving sizes.) We’ve all seen the famous food pyramid. You can use it to your advantage when planning a healthy diet.

Carbohydrates. The highest proportion of foods in your diet should come from this group- 6 to 11 servings per day. These foods provide a valuable energy source in the form of complex carbohydrates (starches). They are also loaded with vitamins, minerals, and fiber. Fiber is critical to maintaining digestive health, and high-fiber diets have recently been found to reduce the risk of some kinds of cancer, especially colon cancer.

Vegetables- You should eat 3-5 servings of vegetables per day. Vegetables provide vitamins like A and C, and folate. They also provide minerals like iron and magnesium and fiber. Dark green leafy vegetables like spinach are a nutritionally rich food.

Fruits- 2-4 servings of fruit are recommended per day. These are important sources of Vitamins A and C, and also some fiber. Fruits have natural sugars, or simple carbohydrates, and can provide a sweet alternative to higher-fat sugar desserts.

Meat/Protein- Meat, poultry, and fish supply protein, along with B vitamins and iron and zinc. You should consume 2-3 servings per day. If you do not eat animal foods, you can choose alternates from this group like beans, soy, and nuts.

Dairy- Milk products provide protein and vitamins, especially vitamin D, but also minerals like calcium. Most people need to consume 2 servings of milk, cheese, yogurt, or other dairy products like ice cream (just watch out for fat and sugar) daily. Because calcium is so critical to bone development, young people under 24 should have 3 or more servings daily. Alternative sources of calcium are dark green leafy vegetables, tofu (made with calcium sulfate), and calcium fortified foods.

Fats, oils, and sweets- These foods are at the top of the pyramid, and should be used very sparingly. Simple carbohydrates - sugars, provide lots of energy, but no other nutritional value and are often considered “empty calories”. There are 3 kinds of fats: saturated fats (found mostly in meat and dairy products), monounsaturated fats (found in olives and avocados) and polyunsaturated (fish and vegetable oils). Saturated, in excess, may lead to high cholesterol levels in the blood and increase the chance of coronary disease. Mono- and polyunsaturated may not lead to clogging your arteries, but they are still fattening! All fats have the same number of Calories per gram. Approximately 25% of your calories should come from fat. You can cut the fat calories if you are trying to lose weight, but you still need some in your diet for the reasons we described earlier.

Once you have the facts about the food groups, the only thing you have to be concerned about is how big a serving really is. That’s where most people blow it. Read the box of cereal and it tells you there are 110 Calories in a serving. Yes, there are, but a serving is one ounce or one cup and most people fill a bowl that holds closer to one and a half cups. Do you have a good idea about how many ounces of meat you eat daily? Your typical plate lunch has your entire quota of protein for the day!

The following provides some guidelines for serving sizes in the different food groups.

Average serving sizes:

milk/yogurt - 1 cup

cheese - 2 ounces (one sandwich size slice)

meat/poultry/fish - 2 or 3 oz (about the size of your palm or a deck of cards)

bread - 1 slice

dry cereal - 1 ounce (1/2 - 3/4 cup of non-granola cereals)

pasta/rice - 1/2 cup

vegetables - 1/2 cup cooked or raw or 1 cup raw, leafy

fruit - 1 piece or 1/2 cup cooked or canned

Reading a nutrition label is a good skill to have when trying to plan your diet. There’s a lot of information there if you know how to decipher it. Labels are required by law to break down the contents into grams of protein, fat and carbohydrate as well as what type of fat or carbohydrate. To figure out what percentage of calories is coming from each category you need some simple math. There are approximately 9 Calories in a gram of fat, 4 Calories in each gram of carbohydrate or protein. So let’s compare two cereals, Kellogg's Corn Flakes and Quaker 100% Natural Cereal.

Kellogg’s Corn Flakes

100 Calories per serving. 2 grams of protein, 24 grams of carbohydrate (21 g complex, 2 g sugar, 1 g fiber) and 0 grams of fat.

Calories from protein = 2 g × 4 Cal/g = 8 Cal, or about 8% *

Calories from carbos = 24 g × 4 Cal/g = 96 Cal, or 96% * (8% from sugars)

Calories from fat = 0 Cal, or 0%

* Since these numbers are approximations, they don’t quite add up to 100%.

Quaker 100% Natural Cereal

130 Calories per serving (1 ounce, but only 1/4 of a cup!), 3 g of protein, 18 g of carbohydrates (8 g complex, 8 g sugar, 2 g fiber), 5 g of fat.

Calories from protein = 3 g × 4 Cal/g = 12 Cal, or about 9%

Calories from carbos = 18 g × 4 Cal/g = 72 Cal, or 55% (44% from sugars)

Calories from fat = 45 Cal, or 35% !

Looks like the Corn Flakes might be a better choice than the Natural Cereal. Beware of labels that say things like “natural”— sugar and fat are both completely natural ingredients, and advertisers know what ploys to use to make you feel good about buying their products. Be aware, too, of labels that claim to be ”light” or “low fat”. Light means different things for different foods. Either the food starts out fatty and half of the fat has been removed or the calorie content has been cut by 1/3. So something like bacon which normally gets 80% of its calories from fat may only have 40% if it’s “light”, but still high in fat! “ Low fat” on a label means no more than 30% of the calories come from fat. But if everything you ate had this percentage of fat you would still get more than the recommended daily percentage of calories from fat.

Activity:

The United States Department of Agriculture and the Center for Nutrition Policy and Promotion have developed a system for rating your diet. Follow the directions on the worksheet, and use the table to help you sort out how many servings of each group and grams of fat you need. You can compare your diet to the typical healthy diet for someone like you.

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