Food is any material consumed to give nutrition to organisms. In nature, food is generally of animal, plant or even fungi, and has important nutrients, including proteins, vitamins, carbohydrates, sugars, or both, that are required for growth. Plants obtain most of their food through the soil where they grow; animals eat meat, eggs or other animals; and fungi consume the living tissues of other organisms. Foods that people consume can be of any form, including plant or animal matter, but are usually in the form of whole foods, such as grains, vegetables, fruits, and legumes. Although, plant matter and animal products are the most common food sources, there are many other food types that are equally important to humans.

There are many food groups, which are separated into two categories – those that are consumed by animals and those that humans eat. Plants have a single food group, which is comprised mainly of carbohydrates, proteins, minerals and vitamins. Animal food groups consist of fats, oils, vegetables, fruits, and legumes. Each food group provides different kinds of nutrients to humans, which is why many people often suffer from nutrient deficiencies because they do not eat enough of certain food groups. Most people usually have a combination of five food groups.

One of the most important food groups, and one of the most difficult to digest, are carbohydrate. A gram of carbohydrate is the basic unit of sugar, which is used to give energy to the body and is used in all cells to maintain health. The three main types of carbohydrates that provide energy to the body are complex and simple carbohydrates. The sugar that is derived from complex carbohydrates is called glucose, while the sugar derived from simple carbohydrates is known as lactose.