To understand human nutrition, it is important to know what food is. Food is any material eaten to give nutrition to an organisms. In humans, food is primarily of animal, plant or fungi origin, and contains necessary nutrients, including proteins, fats, carbohydrates, vitamins, or minerals, depending on the type of food. Plants get their food from the soil through respiration, a process that involves using the air, and photosynthesis, which uses the sunlight to convert food into carbohydrates or starch.

Plants, animals, fungi and bacteria all use different kinds of enzymes to break down food. The main groupings of enzymes are peptide sets, which are chains of amino acids. Peptides can be formed in different ways, depending on species, in a process called peptide bonding. Another way to produce peptides is by the use of arginine, a break down peptide found in proteins and some nonprotein foods, including beans and potatoes. Arginine can also be synthesized by bacteria, yeast and other organisms.

The five food groups are carbohydrates, starches, protein, fat and oils. All of these foods provide energy to the body and all are required by the human body for growth, health and maintenance. In infants, carbohydrates and starches are the primary source of energy. As the child grows, the amount of carbohydrates, protein and fat decrease, while the intake of oils and fats increases. Milk and dairy products are one of the main sources of protein in diets, although eggs are also a good source of protein.

Carbohydrates such as rice, pasta, bread and cereals are important for providing energy to the body. They are also a main source of dietary fiber. Good quality grains and pastas, brown rice and wholemeal bread provide many B vitamins, which are essential for good health. Other foods that are good sources of carbohydrates include potatoes and yams. Foods high in fiber, such as beans, peas, lentils, whole grain rice, etc, are also essential for nutrition, because they help prevent constipation and maintain regular bowel movements.

Many food additives, chemicals and preservatives are introduced into food supplies, either to increase the nutrient value or to make food taste better. Unfortunately, many of these additives and preservatives are harmful to our health. For example, food additives that alter the chemical structure of food are called ‘chemicals’. While food additives, artificial flavors and colorings are ‘food additives’ too. In fact, the FDA, Food and Drug Administration (FDA), defines food additives as ‘any compound added to food in such a manner that it enhances the taste, appearance, consistency, or nutrition of the food’.

Acid is an acid, and in its purest form is alkaline. Certain foods are naturally alkaline and so are the minerals that are part of the food chain; however, some food types are much more acidic than others. Because of this, our bodies must work even harder to break down these acids to keep us from our inevitable consumption of excess acid. The result is that we often eat more food with each meal than we need. To counter this effect, we may resort to eating more food (food that is high in fat) to counter the acid’s effects on our bodies. This process of ‘dual stimulation’ increases the acid production in our body, while at the same time, decreasing the ability of our bodies to absorb the necessary nutrients from foods.