Human Nutrition - Types of Macronutrients

Context: This assessment is aimed at developing the student’s understanding of all of the macronutrients and the role they play in human metabolism. By prescribing this assessment, students are able to build on their understanding of the importance of nutrition in relation to human physiology and health. This assessment allows students to further advance their skills in sourcing and identifying reliable and credible information, which they will incorporate into their written work. Students are able to develop their academic writing skills, as they are expected to express their ideas in a coherent and logical manner, while also enhancing their critical analysis skills, through interpretation and translation of the information researched. Instructions: Students are to discuss all of the following macronutrients listed below, and in a 1500- word report, define and describe the macronutrients in terms of: ? The composition of the macronutrients ?  

Running head: HUMAN NUTRITION 1
Human Nutrition
Name of Author
Institution of Affiliation
Date of Submission

HUMAN NUTRITION 2
Human Nutrition
Introduction
This report discusses three types of macronutrients which include protein, carbohydrate,
and lipids. It describes these macronutrients in terms of their composition, biological functions,
sources, and their recommended daily intake. Besides, the report discusses conditions that can
result as a result of excess intake of these macronutrients. Furthermore, the report discusses the
conditions that can be contributed by the insufficiency of these macronutrients together with
signs and symptoms of these conditions.
1. Protein -Proteins are complex, organic compounds that contain long chains of amino
acids that form the basis of life. Proteins are important nutrients that are required by the
body for various functions.
Composition of protein
Proteins are large complex molecules that are composed of many amino acids. The amino
acids are connected through linkages referred to as peptide bonds. The peptide linkage is
produced the amino group of one amino acid reacts with carboxyl radicals of the other amino
acid. According to (Bjørklund & Chirumbolo, 2017), 20 amino acids are found in proteins that
are grouped into 7. Some examples of these amino acids include glycine, leucine, proline, and
tyrosine. Proteins are also composed of primary, secondary, tertiary and quaternary structures.
The biological functions of protein

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Proteins have various biological functions in human beings. Proteins have been
evidenced to catalyze biochemical reactions. Proteins in this category are referred to as enzymes
that are crucial for the chemical process such as cellular metabolism and digestion (Norton et al.,
2015). Also, proteins act as chemical signaling molecules referred to as hormones. Proteins in
this category are secreted by endocrine cells and released in the body to control specific
physiological processes such as growth and development. Proteins such as hemoglobin and
albumin transport substances in the blood throughout the body. Additionally, proteins act as
defense as they protect the body from attack by foreign pathogens.
Dietary sources of protein
Various diets are rich in protein. One of these diets is meat which includes poultry and
red meat. According to (Cespedes & Hu, 2015), three ounces of meat has about 21 grams of
protein. The other dietary source of protein is fish. Other dietary sources of protein include eggs,
legumes, soybeans, nuts, and seeds.
Recommended daily intake (RDI) of protein
The amount of protein needed to meet one’s basic nutritional requirement is 0.8 grams of
protein per kilogram of body weight. Consuming high amounts of protein than the RDI can result
in an increased risk of health complications. One main condition that is caused by excess
consumption of protein is amyloidosis. Excess proteins build up in organs such as heart, kidneys,
and liver thus affecting their functions. Also, excess protein intake can result in weight gain,
diarrhea, and increased risk of cardiovascular disorders. On the other hand, insufficient protein in
the body can lead to a condition referred to as kwashiorkor. The signs and symptoms of
kwashiorkor include loss of muscle mass, fatigue, edema, loss of body weight and diarrhea.

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2. Carbohydrates
Carbohydrates are complex biomolecules that consist of carbon, hydrogen and oxygen atoms.
They naturally occur as sugars, starches, and fiber. Sugars such as glucose, fructose, and sucrose
are characterized by the sweet taste and contain short-chain carbohydrates. Starches are long
chains of sugar molecules and when consumed, they are broken down into glucose by the
digestive system whereas fibers cannot be digested by the human digestive system.
Composition of carbohydrates
Carbohydrates are composed of elements of carbon, hydrogen, and oxygen in the ratio of
1:2:1 respectively. The basic form of carbohydrates is simple sugars referred to as
monosaccharides. When two simple sugars are combined they form disaccharides whereas when
two to ten simple sugars are combined they form oligosaccharides. Carbohydrates with more
than ten combined simple sugars are known as polysaccharides. Polysaccharides are a long chain
of simple sugars and simple sugars are linked together by linkage referred to as a glycosidic
bond. These long chains of simple sugars may be branched or unbranched and they may include
starch, cellulose, and glycogen.
The biological functions of carbohydrates
Carbohydrates have various biological functions in the body. One of these functions is
that they produce and supply energy to all cells in the body. In this case, glucose acts as a source
of energy and many processes such as respiration depend on glucose as their source of energy.
Carbohydrates are also important in energy storage. The excess glucose is stored in the form of
glycogen in muscles and liver and used later when glucose is insufficient in the body.
Furthermore, carbohydrates act as building macromolecules where some of the glucose is

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transformed into ribose and deoxyribose which are all vital building blocks of ATP, DNA, and
RNA.
Dietary sources of carbohydrates
Carbohydrates are found in a variety of diets. Some of the dietary sources of
carbohydrates include bread, potatoes, beans, corn, popcorn, spaghetti, maize, whole grains, etc.
In these diets, carbohydrates can be in the form of sugars, starches or fibers (Shikany et al.,
2014).
Recommended daily intake (RDI) of carbohydrates
Insufficient or excess consumption of carbohydrates can cause conditions in the body
thus the need to observe the RDI. The RDI in carbohydrates is given in percentage of the total
daily caloric intake. According to (Chang, 2017), the recommended daily intake of carbohydrates
should be based between 45 to 65 % of an individual’s total calorie intake. For example, if one
consumes a 2000 calorie diet, this would equate to between 225 and 325 grams of carbohydrates
daily (Singh, Kesharwani & Keservani, 2017).
Excess consumption of carbohydrates is linked to conditions such as type 2 diabetes and
obesity. Also, according to (Jelsøe, 2015), it has been evidenced that excess consumption of
carbohydrates results in high levels of blood sugars which over time leads to obesity, poor
metabolic health and increased risk of cardiovascular disorders. On the other hand, insufficient
intake of carbohydrates is linked to a condition referred to as ketosis (Sandler et al., 2015). The
signs and symptoms may include fatigue, dizziness, weakness, and dehydration.
3. Lipid-Lipids are molecules that are composed of hydrocarbons. They are characterized
by their insolubility in water, non-polar and soluble in alcohol.

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Composition of lipid
The main composition of lipid is hydrocarbons. The hydrocarbons are in their most
reduced form thus making lipids an outstanding form of energy storage in the body. Thus when
lipids are metabolized in the body, the hydrocarbons are oxidized thereby releasing large
amounts of energy (Song et al., 2016).
The biological functions of lipid
Lipids serve a diverse range of biological functions within the cell. One of these
functions is the storage and provision of energy. Storage lipids such as triacylglycerols release
fatty acid during fasting to provide energy for cell functions. Lipids also act as a structural
component of human cells Lipids such as phospholipids and cholesterol forms part of the cell
membrane and they confer several vital properties such as fluidity and flexibility of the
membrane for its normal functions. Lipids are also involved in the maintenance of temperature.
According to (Senior et al., 2019), layers of subcutaneous lipids such as triglycerides and
sphingolipids under the skin play a critical role in insulating and protecting the body from cold.
Furthermore, steroidal lipids such as testosterone and estrogen are involved in hormonal roles in
the human body.
Dietary sources of lipids
Several parts of lipids are sourced from different sources of diet. Fat particularly
saturated ones are sourced from animal foods such as butter, meat, milk, and cheese. Saturated
fatty acids can also be sourced from tropical oils such as cocoa, coconut and palm oil.
Unsaturated fat which forms a liquid at room temperature can be sourced from vegetable oils
such as peanut, olive and canola oils (Ludwig et al., 2018).

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Unsaturated fats which include omega-6 and omega 3 can be sourced from seafood such as
salmon and shellfish. A recent study has evidenced that nuts and seeds, particularly from
walnuts and soybeans contain omega-6 and omega-3. Furthermore, trans fats which include
hydrogenated fats can be sourced from processed foods such as cookies and potato chips.
Recommended daily intake (RDI) of Lipid
The recommended intake of lipids in adults is 20 to 35 percent of the total calories from
the fat diet. This is similar to 44 grams to 77 grams of lipid if one consumes 2,000 calories a day.
For children who are 2 to 3 years of age, the RDI of fat is 25 to 35 percent. Excess consumption
of lipids can result in the accumulation of fat deposits and cholesterols in artery walls thus
leading to high risk for heart disorders (Forouhi, Sattar & Imamura, 2017). On the other hand,
insufficient or lack of enough lipid in the body leads to a condition referred to as acid lipase
disease. The signs and symptoms linked with lack or insufficient lipids in the body include dry
hair or hair loss, hormonal issues, dry eyes, dry and scaly skin, and mental fatigue.
Conclusion
In conclusion, macronutrients which include carbohydrates, proteins and fats play a
critical role in body functions. They generally provide and store energy, act as a structural
component of the body and help in maintaining the normal functions of the body. Each of these
macronutrients has specific RDI since excess intake or insufficient intake of each of them can
result in serious health conditions.

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References
Bjørklund, G., & Chirumbolo, S. (2017). Role of oxidative stress and antioxidants in daily
nutrition and human health. Nutrition, 33, 311-321.
Cespedes, E. M., & Hu, F. B. (2015). Dietary patterns: from nutritional epidemiologic analysis to
national guidelines.
Chang, L. F. (2017). Effects of dietary fats and carbohydrate on insulin secretion, inflammation
and gastro-intestinal peptides in abdominally obese individuals: A randomized controlled
trial/Chang Lin Faun (Doctoral dissertation, University of Malaya).
Forouhi, N., Sattar, N., & Imamura, F. (2017). Macronutrients and cardiovascular risk in a global
context.
Jelsøe, E. (2015). Dietary guidelines: nutritional health communication versus sustainable food
policy. Journal of Transdisciplinary Environmental Studies, 14(2), 36-51.
Ludwig, D. S., Willett, W. C., Volek, J. S., & Neuhouser, M. L. (2018). Dietary fat: From foe to
friend?. Science, 362(6416), 764-770.
Norton, J. E., Espinosa, Y. G., Watson, R. L., Spyropoulos, F., & Norton, I. T. (2015).
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Sandler, R. S., Lyles, C. M., Peipins, L. A., McAuliffe, C. A., Woosley, J. T., & Kupper, L. L.
(2015). Diet and risk of colorectal adenomas: macronutrients, cholesterol, and
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Senior, A. M., Solon-Biet, S. M., Cogger, V. C., Le Couteur, D. G., Nakagawa, S.,
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Singh, P., Kesharwani, R. K., & Keservani, R. K. (2017). Protein, Carbohydrates, and Fats:
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