The first five letters of the word food refer to the three different sections of food that exist on the planet earth: animal, plant and fungus. Food is any material consumed to supply nutrition to an organisms. Generally, food is generally of animal, plant or fungi origin, and has all necessary nutrients, including vitamins, proteins, carbohydrates, and minerals. Therefore, a diet rich in animal protein results in problems relating to the utilization of these nutrients in plants, whereas a diet high in plant protein results in problems relating to the utilization of these nutrients in animals.
The human body is constantly digesting, absorbing, organizing, processing, storing and eliminating all food we eat. Although the digestive tract in all mammals and most animals is similar, each species expends energy to digest, absorb and organize food, and requires nutrients in order to do so. Animal foods have a shorter time to pass through the digestive system before being eliminated, whereas plant foods take much longer to be digested and absorbed before being expelled. The digestion and absorption of plant foods also involves the utilization of enzymes, hormones, vitamins and other nutrients, which are available only after eating. This implies that animals can obtain all the essential nutrients they require for their existence by consuming only animal products, while plants must rely exclusively on plant products as their source of nutrition.
One of the first problems that arises when following a vegetarian lifestyle is the lack of sufficient fat. Animals feed on fat and even plants cannot survive without it. However, although animal products contain no fat, plant foods can be high in fat content, especially if animal fat is not readily available. Fat provides the calories that animals and plants need to perform their tasks, and the lack of fat in plants limits the amounts of these nutrients that plants can absorb.