Proteins
Fish, seeds, nuts, legumes, tofu, eggs, poultry, seafood, wild and exotic meats, beef and lamb are common sources of proteins. The digestive enzyme Protease assists in the breakdown and absorption of proteins. Proteins are broken down into amino acids by digestion. They provide the building blocks for structure and repair of the body. They transport fats in the body via lipoproteins. Proteins regulate mood via their role in neurotransmitter formation. They are used as an energy source during dieting through gluconeogenesis. Proteins have many functions. They serve as enzymatic catalysts, are used as transport molecules (hemoglobin transports oxygen) and storage molecules (iron is stored in the liver as a complex with the protein ferritin). They are used in movement (proteins are the major component of muscles), they are needed for mechanical support (skin and bone contain collagen-a fibrous protein), they mediate cell responses (rhodopsin is a protein in the eye which is used for vision), antibody proteins are needed for immune protection, control of growth and cell differentiation uses proteins (hormones). These are just a few examples of the many, many functions of proteins.
A balanced diet is one that contains each of the three nutrients: carbohydrates, proteins and fats. Although each nutrient is critical, their combination in the diet is of primary importance. A well-balanced diet consists of 50% carbohydrates, 30% proteins, and 20% fat.
This combination ensures that all the nutrients are included for proper growth and development.
Protein foods are classified in two ways: complete and incomplete. Complete proteins, which come from animal sources such as chicken, fish, dairy and soybeans, contain all the essential amino acids that help build your muscle and body tissue. Incomplete proteins, found in plant foods, such as grains, seeds, nuts, beans and vegetables, provide a varying but limited array of amino acids. A greater variety and amount of incomplete proteins must be consumed to cover all the amino acids needed for protein building. For example, many cereals are low in an amino acid called lysine, but high in methionine and cystine. Lima beans, soybeans and kidney beans are high in lysine but low in methionine and cystine. Many cultures, including Mexican and Indian cultures, have limited animal protein sources but eat combinations of incomplete foods. Examples of appropriate combinations include:
- rice and beans
- cereal and milk
- beans and corn
- bread and cheese