Chapter 15 Section 1: Food and energy

• Key concepts: Why does your body need food? How do the six nutrients needed by the body help carry out essential processes? How can food pyramids and food labels help you have a healthy diet?

• Key terms: nutrient, calorie, carbohydrate, glucose, fat, protein, amino acid, vitamin, mineral, percent daily value, dietary reference intakes

Why you need food

• Food provides your body with materials for growing and for repairing tissues. Food also provides energy for everything you do.

Nutrients and energy• Nutrients – substances in food

that provide the raw materials and energy the body needs

• Energy – – Calorie – the amount of energy

needed to riase the temperature of one gram of water by one degree Celsius

– Most foods contain thousands of calories

– 1 Calorie (capital C) is equal to 1 kilocalorie

– The more Calories, the more energy

Carbohydrates

• Composed of carbon, hydrogen, oxygen• According to nutritionists, 45 to 65% of your diet• Major source of energy and stuff to make cells

• Simple – known as sugars. E.g. glucose

• Complex – many sugars linked together in a chain. E.g. starch, fiber– Starch is digestible and broken down, fiber is not

Fats• Fats – energy containing

nutrients (like carbohydrates) also made of carbon, oxygen, and hydrogen

• Contain more than twice the amount of energy than carbohydrates

• One gram of fat is 9 Calories of energy

• Fats form part of the cell membrane and protect and support your internal organs

Kinds of fats

• Saturated or unsaturated• Unsaturated – usually liquid at room temp• Saturated – usually solid at room temp• Trans fats – made by adding hydrogen to

vegetable oils

Kinds of fats continued

• Cholesterol – waxy, fatlike substance found only in animal products– Your liver makes it, so you don’t need to eat more

• Nutritionists recommend no more than 30% of your diet be fat

Proteins

• Nutrients that contain nitrogen as well as carbon, hydrogen, and oxygen

• Needed for tissue growth and repair, play an important part in chemical reactions within cells

• Need about 10-30% of your diet to be protein

Proteins continued

• Amino acids – proteins are made up of small units called amino acids, linked together to form large protein molecules

• Your body makes about half the amino acids it needs, the others, called essential amino acids, have to come from the food you eat

Proteins continued

• Complete proteins – contain all essential amino acids (meat and eggs)

• Incomplete proteins – missing one or more essential amino acids (beans, grains, nuts)

Vitamins and minerals

• Do not provide energy or raw materials• Vitamins – helper molecules– E.g. vitamin K – helps blood clot

• Fat soluble or water soluble – Stored in fat – A, D, E, K– Water soluble are not stored in the body – C

• Importance – vitamins keep your body healthy and working properly

Minerals

• Not made by living things• Present in soil and absorbed by plants• E.g. calcium

Water

• Water is the most important nutrient• The body’s vital processes cannot take place

without water• All cells in your body are composed mostly of

water• Under normal conditions, you take in about 2

liters of water per day

Guidelines for a healthy diet

• USDA guidelines based on sex, age, physical activity

• Food labels allow you to evaluate a single food as well as compare value of two separate foods

• Serving size • Calories• Percent Daily Value – how much of the nutrient

needed per day is in the food• Ingredients

Dietary Reference Intakes

• DRI – guidelines that show the amounts of nutrients needed every day