Concepts of nutrition

By Jason Smith


Macro-nutrients are needed in relatively large amounts on a daily basis and therefore make up the biggest proportion of dietary intake.Examples include carbohydrate, protein and fat.

1. Carbohydrates are an invaluable source of energy for the body as they are readily available and can be accessed quickly. 1g of carbohydrate contains 4 kcal of energy. Carbohydrates can be split into two groups: simple and complex. Simple carbohydrates are formed from single or double units of different sugars that are easily digested and used to provide the body with a rapid energy source. Fibre is a complex carbohydrate referred to as a non-starch polysaccharide (NSP).

2.The smallest unit of protein is called an amino acid. There are a total of twenty amino acids that the body requires to synthesis protein, and promote growth and normal functioning. Amino acids join to form different proteins. There are eight essential amino acids that the body cannot make and therefore must be obtained from the diet on a daily basis. The remaining amino acids can be made by the body should not enough be obtained through our diet.

3.Fat,Triglycerides form the basic building blocks of fats. Each triglyceride consists of one unit of glycerol and three fatty acids. When digested, fats break down into these two components. Fats are classified as saturated or unsaturated based on their chemical structure. Fatty acids are comprised of carbon atom chains and hydrogen atoms

Examples include carbohydrate, protein and fat.


Micro-nutrients are vitamins and minerals and they represent only a very small portion of our recommended diet.

1.Vitamins are crucial for maintaining correct bodily functions as they allow specific metabolic reactions and prevent disease. Most vitamins our body requires cannot be made in our bodies so must be obtained through our diet. Vitamin D, however, is synthesized by the action of sunlight on our skin and vitamin K can be produced by the bacteria that naturally occur in our large intestine. Vitamins facilitate processes that release energy and also support the immune system.Vitamins are usually grouped into fat soluble (A, D, E, K) or water soluble (B vitamins and C).

2.Minerals are essential for healthy development as they play key roles in enzyme and hormone production, immune system functioning, body structures and muscle contraction. Excessive mineral build up is prevented by absorption and excretion as needed. Some minerals compete for absorption, such as iron, zinc and copper.

Nutritional Requirements & Essential and non-essential carbohydrates

Nutritional requirements vary depending on age, sex, activity, health and other factors such as what stage of life you are at. For Example, more calcium is required during childhood.

For a normal, healthy individual, it is recommended that 50-60% of total calorie intake comes from carbohydrates. However, an athlete will require more. The majority of carbohydrate should be obtained from starchy sources.

Common Terminology

Recommended Daily Allowance (RDA)

Recommended daily allowance, now more commonly referred to as Dietary reference values (DRV) are umbrella terms that explain how much of each nutrient we should have daily. The umbrella term covers:

  • Reference Nutrient Intake (RNI)
  • Estimated Average Requirements (EAR)
  • Lower Reference Nutrient Intake (LRNI)
  • Safe Intake (SI)

Optimal level

Optimal level refers to the process of calculating how much of a nutrient is required based on an individual level. This takes into account individual requirements and lifestyle elements. This process is complicated and requires complex biochemical analysis that is not routine practice.

Safe Intake (SI)

This figure represents an amount of nutrient that is thought to be high enough to meet the needs of the majority of people without causing risk to health. However, it is only an estimate as there may be insufficient information to estimate the distribution requirements of a population.

Estimated Average Requirements (EAR)

These requirements are the most commonly used to assess daily energy requirements.

The Estimated Average Requirements


Male - 55g

Female - 45g


Male - 56g

Female - 46g


Male - 30g

Female - 20g