It is imperative to consider critical factors that determine protein requirements in different groups such as in adults. Protein is an essential component of tissues in the body and a vital nutrient to support growth. The human body has essential compounds, including proteins that always degraded and resynthesised. Proteins help in the healing process by restoring the degrading tissues (Wu & Self 2018). Peptide linkages bond large molecules (protein) comprising of amino acids to support growth. Protein provides the necessary amino acids the beginning elements for the synthesis of tissues as well as the essential tissue proteins. Amino acids are conventionally known as the “currency” of protein nutrients (Zayas 2012). Given that the body is in a constant state of wear and tear, the maintenance of tissues is critical. Therefore, whether ill or healthy, proteins and amino acids are necessary to maintain the repairs of the body tissues.
Essential Functions of Proteins in an Adult
Proteins play critical physiological functions in the body of an adult, including the sick. The nutrients are crucial to forming supervisory compounds in the body. Some of the standard protein substances include all enzymes, some hormones, and various other regulatory components. Without proteins, the body would not produce these important components, while their regulatory functions would be affected. Proteins play a vital role in protecting the body against illnesses (Wu & Self 2018). The body manufactures antibodies upon detecting invading antigens, to help fight the disease. Antigens are giant protein molecules that are created to fight the invading antigens. They support the ailing body to fight against infections and restore the tissues destroyed (Wu & Self 2018). While antibodies still work in an adult body, they tend to be swifter and more efficient in a sick person. During this state, the body requires more proteins than in normal circumstances. In healthy people, some diseases do not have the opportunity to begin due to the working of the antibodies created from proteins.
The body has intracellular and extracellular fluids, those maintained within and those outside the cells. The fluids contained outside the cells are either interstitial, in the spaces between cells or intravascular, within the body’s blood vessels. Proteins are critical in this process by attracting water that supports fluid balance in the different containers (Zayas 2012). Furthermore, the body functions optimally when a balance between acids and bases is evident. Thus, proteins are essential in maintaining this balance in fluids within the body. Proteins achieve this function by accepting and releasing hydrogen ions into the various fluids that balance the acids and bases. As a result, proteins enhance optimal balance for other components, including tissue fluids (McCance & Huether 2018). While proteins support growth and repair of the constantly degrading cells, they play another unlikely role when the need arises. In some conditions, proteins become a source of glucose in the body whenever the supply is limited. From the analysis, it becomes evident that proteins are among the most critical components in the body of a health or a sick adult.
Factors that Influence Protein Requirement
Some researchers have considered the dynamics that influence protein requirements and utilization in the body of an adult under three different groups: the factors that result in the interaction between the diet’s chemical composition and the consumers’ metabolic processes; pathological and physiological factors; and the level at which the consumer meets the energy level. Under the first group of elements, research reveals the presence of sub-influencers such as the protein’s amino acid composition, dietary protein to total energy-yielding sources ratio, and minerals and vitamin levels (Gilani, Xiao, & Cockell 2012). In most practical cases, the degree of caloric intake limits protein anabolism. The limitation might merely depend on the availability of food. Furthermore, it might indirectly depend on the surplus or deficiency of some nutrients. Infections can also play an essential role in the dietary outcome of the individual as related to protein intake (Gilani, Xiao, & Cockell 2012). All the factors play different roles and under different circumstances at the level of protein requirement in the body.
The Interaction between Diet’s Chemical Composition and the Metabolic Processes
Digestibility is an essential factor to consider when evaluating the protein requirement. The FAO/WHO Expert Consultation’s report revealed the importance of protein quality corrected for digestibility as a suitable method in assessing the value of proteins. The scoring pattern is useful in evaluating the level of protein required for both children and adults (Great Britain, Whitehead, & Panel on Dietary Reference Values 1991). The method is also used to measure the quality of protein in the diet consumed by different age groups. However, experts caution approach due to the risk of overestimating needs and underestimating the quality of protein. While caution is necessary for children, adults consume mixed diets, thus minimising the concern for amino acid composition (Great Britain, Whitehead, & Panel on Dietary Reference Values 1991). Regardless of the method used in assessing the quality of protein, digestibility remains an essential factor in determining protein requirement in adults.
The nutritional value of dietary proteins relies on the level at which the nutrients are digested. Consequently, metabolic processes have a significant effect on protein requirements in an adult’s body. Plant proteins are harder to digest than animal proteins since digestive enzymes do not readily enter plant cells due to woody parts and cellulose (van Dooren 2016). As a result, the factor also depends on the type of protein, either animal or plant, since they differ in digestibility
The method of cooking affects the chemical composition of the diet, and thus, digestibility. Heat changes the structure of proteins though not the content of the amino acid. However, overheating might damage the content or lead to products that resist digestive enzymes (Gilani, Xiao, & Cockell 2012). Consequently, the changes affect the level of protein ingested into the gastrointestinal tract through digestion.
The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is the commonly applied measure of protein value. The measure reveals that the level and composition of amino acids in the diet affects the protein requirement (Burd et al. 2013). Therefore, any effects on amino acid composition also affect the level of protein requirement in the body of an adult. The composition of amino acids affects the nutritional value of protein consumed (Burd et al. 2013). Thus, the change modifies the interaction between chemical score and efficient value of protein in the foods and diets consumed.
Physiological Factors and Pathological Conditions
Research on physiological factors and pathological conditions has revealed that during infections and infestations. The level of protein requirement differs from when an adult is healthy. Similarly, age determines the level of protein requirement due to changes in the body and related rate of growth. Diseases lead to lower efficiency of protein utilization due to various factors, such as metabolic disturbances, impaired absorption, and competition for nutrients between the host and the parasite (Areta et al. 2013). At the same time, the body suffers from increasing use of energy in febrile conditions and reduced food intake. The rate of growth in adults differs as they advance in age, suggesting that the protein requirement for young adults differ from older adults. The efficiency of protein utilization also varies in the course of the lifecycle (Rizzoli et al. 2014). Younger individuals require more protein than the elderly due to their high rate of growth. Dietary protein is necessary to meet the growth requirements. Thus, consumption of dietary proteins during different stages should differ.
During Lactation
Lactating mothers require higher intakes due to the protein content in the breast milk. The protein content during the first six months after birth remains constant but reduces with time. Consequently, FAO/WHO/UNU recommends additional proteins to cater for the increasing demand during breastfeeding. The diet for such mothers should include milk protein and vary depending on the kind of food consumed by an individual. In addition, an increase in the intake of protein, including an element to consider the 70% efficiency of dietary utilization is required (Great Britain, Whitehead, & Panel on Dietary Reference Values 1991). Energy needs necessitate the increased need for protein during breastfeeding. However, the recommended additional protein might be greater considering the protein cost of non-protein nitrogen of the breast milk.
Biological Value
The biological value of the diet determines the level of protein requirement in the body. The level is measured by the efficiency of food protein after absorption from the gastrointestinal system. Diets that possess adequate amino acids make it possible for the body to integrate the protein from the food into body proteins effectively (Vilcacundo & Hernández-Ledesma 2017). Thus the biological value of the diet depends on the closeness in the reflection of amino acids to the proteins contained in tissues in the body. Proteins turn into amino acids in the body tissues depending on the level of the match. Vilcacundo and Hernández-Ledesma (2017) add that the adult body requires more proteins that are a close match and quickly change into body proteins. Some foods such as the egg-white protein have a very high biological value. Furthermore, animal proteins differ from plant protein in biological value as the latter varies from one type of diet to another. Therefore, proteins that are not a match are excreted as urea.
Protein Efficiency Ratio
The quality of food protein is measured using tools such as the protein efficiency ratio (PER). The measure performs a comparison of the level of weight (in grams) achieved in growth after consuming a particular amount of protein for a specific period. The amount of protein should come from a specific type of protein. The protein efficiency ratio of a diet determines the biological value of the food (Zayas 2012). The two measures the level of protein that is retained in the body tissues. The amount of animal proteins is higher than that of plant proteins due to their incompleteness.
Chemical Score of Protein
The chemical score estimation can also determine the protein quality of a diet. The chemical score of a food is calculated using the level of every essential amino acid that a gram of the food provides divided by the amount considered ideal for the gram of food protein (Sarmadi & Ismail, 2010). The ideal depends on the optimal amount of amino acid required by the body from a gram of food protein. The chemical scores vary from 0 to 1.0 (Zayas 2012). Therefore, such value determines the level of protein required by the body of an adult.
The Need to Meet Energy Level
Caloric insufficiency is another essential factor that influences protein requirements in an adult body. Research reveals a relationship between protein and energy requirements (Houston et al. 2008). The efficiency of utilization of protein reduces when the intake of calories goes below a particular optimum level. Notably, the level of calorie intake in an adult diet fluctuates from one day to another. The changes depend on, among other things, the level of exercise or training. Thus, active adults tend to consume more calories than less active ones (Witard, McGlory, Hamilton, & Phillips 2016). The level of fluctuation also differs depending on what the consumer does with fat and carbohydrate intake. Therefore, high caloric intake affects the level of protein the body requires.
The Protein Content of Foods
The protein content of foods determines the level of nutrients required by an adult body. The level of requirement is determined by nitrogen balance, including the overall nitrogen in the diet as well as the excreta. Generally, the actual, in this case, is based on nitrogen instead of protein. The food composition tables measure the overall nitrogen in the diet using the Kjeldhal technique (Rizzoli et al. 2014). The outcome of the method is multiplied by a particular factor in calculating the content of protein in the diet. In general, most protein diets have approximately 16 percent nitrogen. Multiplying the entirety of dietary nitrogen by 6.25 gives the estimated amount of “crude protein” or protein intake. Notably, the level of nitrogen in protein diets varies across foods, with some having a lower percentage than others. The Joint FAO/WHO Committee (FAO/WHO 1973) recommended essential elements to consider when converting nitrogen to protein (Consultation 2011). The conversion depends on the percentage of nitrogen in the diet.
General Considerations for Adults and Elderly
The FAO/WHO/UNU Consultation reviewed evidence from research on nitrogen balance to determine the level of the protein requirements of young male adults. The study sets the safe intake of good quality, highly digestible proteins at 0.75 g/kg per day for the particular group (Consultation 2011). However, the review revealed a limitation in data for adult women. The researchers established no difference between males and females in obligatory urinary nitrogen loss. In addition, based on the short-term nitrogen balance, the research on young females consuming proteins from diverse sources revealed no much variance from that of adult males. Consequently, it is possible that the utilization efficiency of protein from food to meet the physiological requirements is fundamentally similar (Consultation 2011). Consequently, the expert advice suggests a similar intake of dietary protein for both adult males and females.
From a review of the previous evidence, researches tend to agree that comparable measures should be used for elderly individuals. The DRI Committee of IOM (2002) made similar recommendations for males and females, as well as all adults, young and older. The 1985 FAO/WHO/UNU recommendations are the basis for the revised RNI for protein intake for such individuals. The organization recommends 1.00 g protein/kg body weight/day. However, the outcome is adjusted for 80 percent of protein quality (Consultation 2011). The reference weight for the participating females and males are 55 kg and 62 kg respectively. In this case, the weight is 57 kg for elderly males and 49 kg for elderly females (Consultation 2011). Consequently, research shows that the level of protein requirement for adults, whether young or old is comparable. However, other factors such as the health of the participant and the nature of the diet determine the level of protein requirements.
Conclusion
Assessment of dietary values plays a vital role since every individual require different levels of protein. Notably, protein is necessary for the growth since body cells are damaged and new ones formed. The discussed factors are critical in determining the diet of an adult. Research shows the importance of considering all the elements because the level of protein utilization in adults is similar for both males and females as well for the elderly. In addition, significant differences on protein requirements for health and ailing individuals primarily due to caloric insufficiency and the wearing out of the body due to the infection and infestation is evident. The information is critical when making dietary decisions. For instance, the quantity of proteins required might increase when a person is unwell or active when one is healthy and inactive. People should understand the circumstances under which the differences in energy requirements occur. It also informs the decision on whether to consume animal or food protein depending on the protein requirement.
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