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 use B) 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 Nutrients To 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 fat Saturated = 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 vitamins Vitamins A, D, E and K They 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 C They 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 NutrientEnergy Content kj/gCal/g Carbohydrate174 Fats379 Proteins174 Waternil Vitaminsnil Mineralsnil

Energy Value Carbohydrates and fats are the body’s major source of energy Proteins 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 Requirements The 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: Age Sex Weight Level of physical activity A typical adolescent girl requires calories/day A typical adolescent boy requires calories/day

Energy Output for Various Activities Activity (1 hour)Required Calories Sleeping or resting60 Sitting90 Standing120 Walking170 RunningOver 300

Canada’s Food Guide