Nutrition involves all the processes involved in the absorption, use and elimination of the substances needed to keep our bodies in good working order.

This involves: A) The digestive system: needed to transform the

food we eat into nutrients our cells can useB) The respiratory system: oxygen is needed to

transform the nutrients we eat into chemical energy

C) The cardiovascular system: our blood circulates the nutrients and oxygen to our cells.

D) The urinary system: needed to filter our blood and eliminate waste in liquid form

Nutrition

Essential NutrientsTo function, the human body must have nutrients. The nutrients known to be essential for human beings are:

1) proteins 2) carbohydrates 3) fats 4) water 5) vitamins 6) minerals

A nutrient is a substance found in food that is used by the body to meet important needs.

Proteins

Did you know that protein is the body’s most abundant substance, except for water?

Carbohydrates

Did you know that carbohydrates (carbs) account for about 1/2 of the calorie intake for most Americans?

And up to 4/5 of the calorie intake in diets of African and Asian populations?

Carbohydrate-rich foods are also the main sources of protein for most of the world.

Sugars (monosaccharides & disaccharides) provide energy, but NO nutrients. This is why it is called an “empty calorie” food, and is not an essential nutrient.

Fats

There are 3 types of fats:Unsaturated = good fatSaturated = bad fat

Usually solid in form and of animal origin (meat) Saturated fats can raise the level of cholesterol in

the blood. Cholesterol is a natural waxy substance

made by the body.It helps to form digestive juices It is present in the body no matter what is eaten. Excess cholesterol in the walls of the blood vessels

may lead to a heart attack or stroke.

Water

Vitamins

Fat-soluble vitaminsVitamins A, D, E and KThey are digested and absorbed with the

help of fats that are in the diet.They can be stored in the body for long

periods (in fatty tissue and liver).Water-soluble vitamins

Vitamins B (there are several kinds) and CThey are not stored in the body for long,

therefore, good sources should be eaten every day!

Minerals

Most minerals are easy to obtain in the required quantities.

Some people, especially teenage girls and women, might need to take iron supplements.

Iron: helps build red blood cells, & helps carry oxygen from the lungs to each body cell

Calcium: builds bones and teeth, & necessary for blood clotting

Phosphorus: works with calcium to make strong bones and teeth

Other important minerals: sodium, potassium, iodine, magnesium, zinc, and copper.

The Energy Value of Food

A joule (J) is the typical measurement unit for energy

With food, however, calorie (cal) is commonly used to measure the energy content of foods.

1 cal = ~ 4000 J or 4 kJ (kilojoules)Energy is used for everything we

do, from breathing to talking and even sleeping!

Average Energy Content in Nutrients

Nutrient Energy Contentkj/g Cal/g

Carbohydrate

17 4

Fats 37 9Proteins 17 4Water nil nilVitamins nil nilMinerals nil nil

Energy ValueCarbohydrates and fats are the body’s

major source of energyProteins are mostly used to build and

repair body tissue, but may be sometimes used as an energy source if there are not enough carbohydrates or fats to meet our energy needs.

Water, vitamins and minerals are NOT sources of energy

Energy RequirementsThe amount of energy you need to

perform your daily activities determines the amount of food you should eat.

This is different for every person depending on:AgeSexWeightLevel of physical activity

A typical adolescent girl requires 1800- 2400 calories/day

A typical adolescent boy requires 2200- 3200 calories/day

Energy Output for Various Activities

Activity (1 hour) Required Calories

Sleeping or resting

60

Sitting 90

Standing 120

Walking 170

Running Over 300

Canada’s Food Guide