Explain how energy is produced through diet and digestion
Given the diversity of animal life on our planet, it is not surprising that the animal diet would also vary substantially. The diet must be balanced to provide the minerals and vitamins that are required for cellular function.
What You’ll Learn to Do
- Describe the essential nutrients required for cellular function that cannot be synthesized by the animal body
- Identify common nutrients essential to life
- Explain how energy is produced through diet and digestion
The learning activities for this section include the following:
- Food Requirements
- Essential Nutrients
- Food Energy and ATP
- Self Check: Nutrition and Energy Production
Nutrition and the immune system: an introduction
Nutrition is a critical determinant of immune responses and malnutrition the most common cause of immunodeficiency worldwide. Protein-energy malnutrition is associated with a significant impairment of cell-mediated immunity, phagocyte function, complement system, secretory immunoglobulin A antibody concentrations, and cytokine production. Deficiency of single nutrients also results in altered immune responses: this is observed even when the deficiency state is relatively mild. Of the micronutrients, zinc selenium iron copper vitamins A, C, E, and B-6 and folic acid have important influences on immune responses. Overnutrition and obesity also reduce immunity. Low-birth-weight infants have a prolonged impairment of cell-mediated immunity that can be partly restored by providing extra amounts of dietary zinc. In the elderly, impaired immunity can be enhanced by modest amounts of a combination of micronutrients. These findings have considerable practical and public health significance.
Nutrition is the science of food and its relationship to health – how the human body uses food and processes the nutrients it contains to enable the body to perform functions (i.e. the heart to beat, the lungs to breathe, the kidneys to filter blood, the brain to think etc.).
Encompassed in this definition is how much energy (kilojoules) a body needs to maintain a healthy weight. Energy is delivered to the body through foods. Any energy consumed (in the form of carbohydrates, protein or fat) and not used for metabolism, growth or physical activity will be stored as body fat. There are many factors that dictate how much energy a person needs, but in simple terms the more the body moves, the greater the amount of energy will be needed.
The kilojoule is the measure of energy used in Australia. It is the International unit for energy, but some countries (e.g. USA) still use the calorie.
The conversion is: 4.2kJ = 1 calorie. We use it to determine how much energy a food will provide when we eat it.
The nutrients that provide energy are commonly referred to as macronutrients (carbohydrates, lipids, and proteins). Carbohydrates and proteins provide a similar amount of energy per gram of food. Lipids are a concentrated source of energy and provide almost twice the amount of energy than that supplied by proteins and carbohydrates.
For your information only:
CHOs = 16 kJ per gram of CHO
Protein = 17 kJ per gram of protein
Lipids = 37 kJ per gram of lipid
Children aged between 4-18 years require
6500 to 14000 kJ per day. The approximate number of kilojoules a child consumes per day will depend on their age and physical activity level. The values given are for average physical activity only. For further information, please refer to the Nutrient Reference Values for Australia and New Zealand website.