Dietary guidelines : Protein

Protein is a basic building block of humans. Amino acids are the basic building block of protein.

Protein can also serve as a fuel source.

Protein is second to water as most common element of human body.

Proteins are molecules consisting of one or more long chains of amino acid called polypepetides. Proteins differ from one another in their sequence of amino acids.

Proteins are important in the structure (building and maintaining) and the functioning of all cells.

Protein is a major component of all cells especially muscle, hair and skin.

Protein is needed for all biochemical reactions in the human body.

Once formed, proteins only exist for a certain period of time and are then degraded and recycled by the cell's machinery through the process of protein turnover. A protein's lifespan is measured in terms of its half-life and covers a wide range. They can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells.

There are 20 amino acids in the human body.

Nine are essential amino acids (They cannot be synthesized by the body). phenylalanine, valine, threonine, trytophan, methionine, leucine, isoleucine, lysine and histidine.                                                                                                        

There are five amino acids which humans are able to synthesize in the body. alanine, aspartate, asparagine, glutamine and serine

There are six conditionally essential amino acids which the body is able to synthesis under certain conditions.

arginine, cysteine, glycine, glutamine, proline and tyrosine.

Sources of protein.

Meat, dairy products, eggs, fish, legumes (peas, beans and lentils) are sources of complete protein.

Whole grains and cereals.  Have limited of lysine or threonine. Whole grains and cereals with a concentration greater than 7.0% of amino acids, are buckwheat, oats, rye, millet, maize, rice, wheat, sorghum, amaranth, and quinoa.

Foods with protein concentrations greater than 7.0% percent are nuts, pumpkin seeds, hemp seeds, sesame seeds, and sunflower seeds.

Vegetables are poor sources of protein. The protein content of yams,  cassava and sweet potato is between 0 and 2 percent.

Fruits are a poor source of amino acids.

Legumes, cereals, nuts and seeds, and animal protein contain different proportions of all amino acids especially lysine, threonine and tryptophane.

No food is complete protein. Most foods containing protein also contain carbohydrates, oil, fibre, vitamins and minerals.

No food is the complete protein. The best source of protein is often a combination of various foods, because different foods are rich in different amino acids.

Digestion

Digestion involves breaking down peptides containing multiple amino acids into peptides containing 1, 2, 3 or 4 amino acids.  Digestion involves hydrochloric acid and enzymes present in the gastro-intestinal tract.

Absorption rates depend on type of protein.

Dietary requirement of protein depends on:

Body weight

Rate of growth and development (during childhood increased need of protein)

Physical activity

Carbohydrate intake

Pregnancy or breastfeeding

Presence of illness or injury

Recovering from malnutrition, trauma or an operation

Adult women need 46gm/day

Adult men need 56gm/day

Based on weight of 57 kg female and 70 kg male and 0.8 gm/kg and a sedentary lifestyle.

Active people need 1.6gm/kg-1.8gm/kg