Carbohydrates and Proteins

Carbohydrates
Calories/gram: 4
Carbohydrates may be classified as monosaccharides, disaccharides, or polysaccharides by the number of monomer (sugar) units they contain. They are found in large proportion in foods such as rice, noodles, bread and other grain-based products. Monosaccharides contain 1 sugar unit, disaccharides contain 2, and polysaccharides contain 3 or more. Polysaccharides are often referred to as complex carbohydrates because they are long chains of sugar units, whereas monosaccharides and disaccharides are simpler. The difference is important because complex carbohydrates take longer to digest and absorb since their sugar units are processed one-by-one off the ends of the chains; the spike in blood sugar levels caused by substantial amounts of simple sugars is thought to be at least part of the cause of increased heart and vascular disease associated with high simple sugar consumption. Simple carbohydrates are absorbed quickly and thus raise blood sugar levels more rapidly.


Protein
Calories/gram: 4

Most meats such as chicken contain all the essential amino acids needed for humans.
Proteins are the basis of animal body structures (eg, muscles, skin, hair etc.). They are composed of amino acids, sometimes many thousands, which are characterized by inclusion of nitrogen and sometimes sulphur. The body requires amino acids to produce new body protein (protein retention) and to replace damaged proteins (maintenance). Amino acids not needed are discarded, typically in the urine. In animals, amino acid requirements are classified in terms of essential (an animal cannot produce them internally) and non-essential (the animal can produce them from other nitrogen containing compounds) amino acids. Humans use about 20 amino acids, and about ten are essential in this sense. Consuming a diet that contains adequate amounts of essential (but also non-essential) amino acids is particularly important for growing, pregnant, nursing, or injured animals, all of whom have a particularly high requirement. Protein nutrition which contains the essential amino acids is a complete protein source, one missing one or more is called incomplete. It's possible to combine two incomplete protein sources (eg, rice and beans) to make a complete protein source.
Dietary sources of protein
Plant sources include beans, peas, pulses, whole grains, nuts and oil seeds; while red meat, poultry, fish, milk, cheese, yogurt and eggs are obtained from animals. Red meat is a good source of essential amino acids and iron and is traditionally regarded as 'first class' protein. But too much consumption of red meat may be harmful as it is a major source of undesirable saturated fat. One can eat more fish or chicken without the fatty skin instead of excess red meat. Vegetarians can obtain plenty of both from plant sources, whole grain cereals and from low fat diary products. A protein deficiency especially in infants and growing children can cause growth retardation, severe wasting of muscle