Dietary protein daily requirement

C. The main role of dietary proteins is provision of the amino acid building blocks for synthesis of cellular proteins, many of which require daily renewal to maintain physiologic functions and respond to the needs of the body. 

Every patient with diabetes requires some form of dietary assessment, and often therapy. This is important to allocate the relative amounts of energy derived from carbohydrate, protein and fat of total recommended daily calories in proportion to the patient s body weight and height and daily requirements, while avoiding atherogenic diets. Diets with high carbohydrate content (50-60%), low fat (30-35%) and adequate protein (10-15%) is recommended. Fibre-rich foods are preferable. The use of non-nutritive sweeteners (saccharin, aspartame, ace-sulfame K and sucralose) are acceptable. Alcohol intake should be assessed since excess consumption... 

The average daily dietary intake of protein in North America is about 100 g compared with an estimated requirement for adults of 50 to 70 g. In addition to dietary protein, another 50 to 60 g of protein enters the intestinal contents daily in Gl secretions and from desquamated mucosal cells. Normal daily fecal loss of protein is about 10 g. 

The answer is c. (Murray, pp 123-148. Scriver pp 2367-2424. Sack, pp 159-175. Wilson, pp 287-317.) The daily intake of 62.5 g of high-quality protein is above the minimum daily requirement for a 70-kg adult (45 g protein per day). As the obligatory nitrogen losses are covered by the dietary intake, this man will be in nitrogen balance (i.e., 0) and nitrogen loss will equal nitrogen intake. 

The daily requirement for degradable protein (ERDP) is given by (FME X 11) g, where FME (MJ/day) is the fermentable metabolisable energy intake. The contribution of dietary ERDP to satisfying metabolisable protein demand may be calculated, as for the cow, as 0.6375 X ERDP. 

The remaining essential amino acids should be provided in the proportions relative to lysine provided in Table 13.7 in Chapter 13. For example, the methionine requirements for lactation are 0.30 of that of lysine, resulting in a daily methionine requirement of 19.5 g/day or 2.6 g/kg diet. Conducting a similar calculation for all the essential amino acids, and assuming that the non-essential amino acids are typically 1.5 times this level, results in a minimum Heal digestible protein content of 120 g/kg, or a dietary protein level of approximately 143 g/kg diet (120/0.84). 

The average minimum requirement of dietary protein for N equilibrium in the adult need only contain 6 gm of essential amino acids. However, the diet of 90 gm of protein usually consumed provides about 45 gm of essential amino acids. To this are added the essential amino acids entering the gut as endogenous proteins. In consequence, about 75 gm of essential amino acids are absorbed daily. This amount can be contrasted with the total amounts of essential and non-essential amino acids in the plasma, namely 0.2 and 0.5 gm. It is thus to be expected that free amino acids will be rapidly transported out of the blood into the tissues. It will also be noted that, although the tissues contain some 70 gm of free amino acids, only 10 gm are as essential amino acids. Nevertheless, the daily turnover of 300 gm of body protein requires 150 gm of essential amino acids. Most of this has to come from recycling of essential amino acid released by the tissues, since the diet customarily provides about 45 gm essential amino acids. Nitrogen equilibrium can still be achieved when the essential amino acid content of the diet is as low as 6 gm. This implies very efficient recycling of amino acids within the body. 

All but two of the 127 countries studied meet or exceed the recommended daily requirement of 38.7 g of protein per person. But it should be noted that, on a worldwide basis, much protein is diverted to meet dietary energy deficits it is estimated that 11% of the energy comes from protein. Remember, too, that many of the countries that are low in total protein depend to a large extent on protein from plant sources which is required in greater amounts than animal protein. 

The presence of proteins in the diet is essential for health. An important question, therefore, is what is the minimal amount of protein that must be provided to maintain health It is not an easy question to answer. Even when no protein or amino acid is consumed, in an otherwise adequate diet, urea is lost from the body due to body protein break down. The daily loss of protein is about 0.34 g per kg or about 24 g protein each day for a 70 kg person (i.e. when no protein is consumed). However, this amount does not represent the minimal intake required, since other factors, (such as the amount of energy consumed, other components in the diet, and trauma physical activity can affect this amount.) The recommended dietary allowance (RDA) for a young adult is 0.8 g per kg per day (Table 8.6). 

Osteoporosis is a disease or metabolic disturbance, particularly in postmenopausal women, that indicates a need for a very high dietary calcium intake. High calcium requirements appear to be related to the very high protein intake of the modem Western diet. A decreased protein intake, as can be obtained on a total vegetarian (vegan) diet, can allow for calcium balance, in a variety of age groups, from one third to one fifth the amount of daily calcium required with a Western diet. 

Dietary requirements for AAs and protein usually are stated as proportions of the diet. However, the level of feed consumption has to be taken into account to ensure that the total intake of protein and AAs is appropriate. The protein and AA requirements derived by the NRC (1994) relate to poultry kept in moderate temperatures (18-24°C). Ambient temperatures outside of this range cause an inverse response in feed consumption i.e. the lower the temperature, the greater is the feed intake and vice versa (NRC, 1994). Consequently, the dietary levels of protein and AAs to meet the requirements should be increased in warmer environments and decreased in cooler environments, in accordance with expected differences in feed intake. These adjustments are designed to help ensure the required daily intake of AAs. 

The human organism contains 1-1.4 kg calcium, and about 1% of this is in the extracellular fluid. The rest is largely in bone. The serum calcium concentration is 9-11.5 mg/dL, of which 4.5-5.0 mg/dL is in the free, ionized, biologically active form. The rest is protein bound or complexed with a variety of chelators, such as citrate. The daily dietary calcium requirement is 400-500 mg, and each day, 300-400 mg calcium is lost in the urine and an additional 150 mg in the feces. Inorganic phosphorus (largely as HP042 ) amounts to 2.7-4.5 mg/dL in adult serum. 

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