Fundamentals of Human Nutrition/Dietary intake
5.5 Dietary Intake:PROTEIN
Dietary Intake: Protein AMDR/DRI VALUES Protein is needed in the body because it repairs body tissue, regulates hormones and enzymes, and helps antibodies function so that it can fight infection. Proteins are made up of amino acids, which give structure to muscles and tissue. Therefore, the intake of protein is essential for the body to function. The Acceptable Macronutrient Distribution Range (AMDR) for proteins for adults is 10 to 35 percent. The amount of protein a person is supposed to consume per day is known as the Dietary Reference Intake (DRI). For protein, the DRI is 0.36 grams of protein per pound of body weight or .8 grams of protein per kilogram of body weight. An average man should consume about 56 grams of protein per day, and an average woman should consume about 46 grams per day. The average man weighs more than the average woman; therefore, men should eat more protein. For example, if a woman weighs 135 pounds, the DRI for protein would be 48.988 grams of protein. We can calculate this by using the weight in kilograms and multiplying it by 0.8. 135 pounds equals 61.235 kilograms; therefore, you can multiply 61.235 by .8, which will equal 48.988 grams. (Protein in the Vegan Diet) Pregnant women obviously need more protein. Women should average 71 grams if they are pregnant or breastfeeding.
Vegetarian Source of Protein
Vegetarians may have a hard time eating enough protein. This is because meat, fish, eggs, and dairy are usually the main sources of protein. The problem with meat is that it is most likely high in cholesterol. “Meat and poultry choices should be lean or low-fat.” (Choose MyPlate, 2015) If it isn’t lean or low-fat, it can be high in cholesterol and also make you gain weight. This is bad because it can lead to coronary heart disease, which can result in a heart attack. If you are a vegetarian, foods that you may wish to consume include green peas, quinoa, pumpkin seeds, dried beans, peanut butter, and almonds. This may be needed for people that don’t eat meat. Vegans and Vegetarians on average eat less protein than people who eat meat. (Protein in the Vegan Diet) People that don’t eat enough protein can also take protein supplements. The majority of people don’t need these supplements. However, some athletes who need to gain weight may take them. Also, it may be essential for bodybuilders to take these supplements. Some bodybuilders wake themselves up so that they can eat protein.
How Protein Affects the Body
Protein can make you lose weight. This is because protein can make people feel extremely full so they would consume fewer calories throughout the day. Protein intake can also help you gain muscle. This is because in order to gain muscle, one person must gain more muscle protein than the muscle that is being broken down after a workout. For example after lifting weights, many people will consume a protein shake in order to repair muscles so that the muscle can get bigger. However some athletes believe they should be eating protein throughout the time. Therefore, they might eat protein an hour after workout instead of right away.
To gain muscle, the body needs to synthesize more muscle protein than it breaks down. Animal proteins support muscle adaptations with weight or other exercise training more easily compared to plant based proteins since proteins from animals contain more complete amino acids. To increase muscle mass for an individual who regularly lifts weights, it is recommended that they intake a range of 1.2-1.7 grams of protein per kilogram of body weight per day. A common but false recommendation is to get a gram of protein per pound of body weight. This much protein intake has no benefit to gaining muscle mass and may actually cause negative consequences. No more than 2 grams of protein per kilogram of body is necessary to build muscle.
Choose MyPlate. (2015, February 23). Retrieved December 1, 2015, from http://www.choosemyplate.gov/protein-foods Protein in the Vegan Diet. Retrieved December 7, 2015, from http://www.vrg.org/nutrition/protein.php Turner, L., & Whitney, E. (2011). Study guide: Understanding nutrition, Twelfth edition. Belmont, CA: Wadsworth.
Gunnars, K. (2014, March 20). Protein Intake – How Much Protein Should You Eat Per Day? Retrieved December 1, 2015, from http://authoritynutrition.com/how-much-protein-per-day/
The recommended dietary allowance (RDA) for an average person is 0.8g/kg, but some groups may need a higher amount (such as children, women during pregnancy and lactation, or athletes). An upper level has been set at 30% of the total calorie intake. 
There are three main risks associated with high protein diets: dehydration, kidney damage and bone damage.
- Dehydration occurs by the need to excrete large amounts of urea and other nitrogenous wastes from protein catabolism. It can be prevented by increasing fluid consumption. 
- Kidney damage has been proved in people with prior renal problems. Kidneys would not be able to eliminate all the waste products of protein metabolism. However, no studies have shown significant proof of this link in healthy individuals.  
- Bone damage has been a controversial topic over the last years. Some studies claim catabolic effect and others claim anabolic effect. Those that claim catabolic effect (lose of bone density) blame the acids generated by the oxidation of aminoacids. These acids would destabilize the acid-base balance. In order to excrete the excess acid load, the bone will release calcium, magnesium and other compounds to serve as the buffers. Studies claiming anabolic effect point at the intake of fruits, vegetables and dietary calcium to balance out the excess of acid.  [3-7]
Proteins serve an immense role such as being enzymes, aiding in cell structure, hormonal function, and their role in being transport carriers. The human body is nothing without proteins (Dietary Reference Intakes: Macronutrients, 2005). There is rising concern about the media, popular diet books, and health professionals promoting high protein diets without enough scientific data. These sources are promoting high levels of protein intake in order to manage weight and increase muscle synthesis (Bilsborough & Mann, 2006). Although the importance of protein can be clearly seen, excess protein intake can lead to major problems such reduced liver and brain function, weight gain, and high cholesterol.
Excess protein has the potential of reducing liver and brain function due to the extra production of ammonia by the human body. Ammonia is a toxin produced by the liver, and in normal levels, it is effectively removed from the body by the urinary system. During excess protein intake, overproduction of ammonia results, and this causes the liver to be overworked. This then leads to toxin buildup in both the liver and the bloodstream. This specific issue can lead to hepatic encephalopathy, and this condition is associated with decline in brain in nervous system function (Appleby & Media, 2015).
Weight gain is another problem associated with excess protein intake. The human body is only able to use up a certain amount protein daily; therefore, the excess protein is stored as fat. Each gram of protein has 4 calories, and these extra calories quickly add up by the end of the week if additional protein is continuously being eaten (Appleby & Media, 2015).
Another problem associated with high levels of protein intake is high cholesterol. High cholesterol is mainly correlated with high protein foods, such as from animal products, which contain ample amounts of cholesterol. High cholesterol leads to hardened arteries, which may in turn lead to severe health problems like heart attack and stroke. According to the guidelines set out by the National Heart, Lung and Blood Institute, cholesterol intake should not be more than 200 milligrams per day. Since protein-rich animal products contain high levels cholesterol, it is important to eat in moderation in order to stay within guideline range (Appleby & Media, 2015).
The recommended plan for protein intake laid out by the Institute of Medicine, is that 10-15 percent of the calories taken in daily should be high rich protein. Women need about 46 grams of protein daily, while men need about 56 grams of protein daily. Specifically, people who partake in high levels of physical activity need more protein daily as opposed to others; however, this must be checked with a medical doctor before increasing protein intake (Appleby & Media, 2015).
While protein can slow digestion and help one feel full, too much protein is a dangerous thing. For an 80-kilogram person, the liver can’t metabolize much more than 221–301 grams of protein per day; this is about 2.76-3.76 grams of protein per kilogram. Too much protein consumption can result in ammonia and urea buildup in the bloodstream, which is toxic to the brain. The liver usually converts amino acids from protein into urea to be removed by the kidneys but when too much protein is consumed, the liver will start to slow down and fail to convert ammonia into urea. High protein consumption coupled with very low fat and carb intake can lead to a form of protein poisoning known as rabbit starvation. If needed, the human body can only utilize about 1000 calories from protein as energy a day. This is because the liver is only capable of producing about 250 grams of glucose from protein and any more than this is useless and dangerous. Attempting to consume a normal 2000-calorie based diet on mostly protein will lead to rabbit starvation. The name comes from the fact that humans cannot live on a diet of only rabbit meat because it is too lean with only about 8% fat.
Appleby, M., & Media, D. (2015). Three Problems Associated With Too Much Protein Intake. Retrieved from http://healthyeating.sfgate.com/three-problems-associated-much-protein- intake-6546.html
Bilsborough, S. & Mann, N. (2006, April 1). A Review of Issues of Dietary Protein Intake in Humans. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/16779921?dopt=Abstract&holding=f1000,f1000m,isrctn
Dietary Reference Intakes: Macronutrients. (2005). Retrieved from http://iom.nationalacademies.org/Global/News Announcements/~/media/C5CD2DD7840544979A549EC47E56A02B.ashx
Rabbit starvation results from low fat, low carb, protein-only diets. (n.d.). Retrieved December 2, 2015, from http://www.raising-rabbits.com/rabbit-starvation.html
 Sareen Grooper, Jack Smith (2009). Advanced Nutrition and Human Metabolism.
 William Martin, Lawrence Armstrong and Nancy Rodriguez (2005). Dietary protein intake and renal function. Retrieved from http://www.nutritionandmetabolism.com/content/2/1/25
 Uriel Barzel, Linda Massey (1998). Excess dietary protein can adversely affect bone. Retrieved from http://jn.nutrition.org/content/128/6/1051.full
 Robert Heaney (1998). Excess dietary protein may not adversely affect bone. Retrieved from http://jn.nutrition.org/content/128/6/1054.full
 Bess Dawson-Hughes (2003). Interaction of dietary calcium and protein in bone health in humans. Retrieved from http://jn.nutrition.org/content/133/3/852S.full
 Robert Heany and Donald Layman (2008). Amount and type of protein influences bone health. Retrieved from http://ajcn.nutrition.org/content/87/5/1567S.full
 Robert McLean et al. (2011). Dietary acid load is not associated with lower bone mineral density except in older men. Retrieved from http://jn.nutrition.org/content/141/4/588.full
In the United States, protein deficiencies are not as common as protein excess is. This is because almost all of our food has a significant amount of protein in it. Protein-rich foods provide us with essential amino acids that are needed for daily function. Foods that supply us with essential amino acids include, but are not limited to, meat, dairy products, and eggs. (Tuso, Ismail, Ha, Bartolotto, 2013)
Essential amino acids also come from various combinations of plant-based foods such as quinoa. (Tuso, Ismail, Ha, Bartolotto, 2013) While protein deficiency is not a rampant issue within the United States, it can be detrimental for those who suffer from it. Those who suffer from protein deficiencies are unable to perform daily tasks properly and suffer from many harmful symptoms.
Here are different types of protein deficiencies according to Protein Deficiencies Diseases:
- Protein S deficiency
- Protein C deficiency
- Protein S and C deficiencies are not a result of malnutrition but are instead inherited disorders. (Chen, 2014) In contrast to this, marasmus and kwashiorkor are both results of extreme malnourishment and deficiencies of protein.
Protein S and C
People who are deficient in protein S and C are lacking the proteins that are present in the fluid of the blood. Protein S and C deficiencies are rare congenital disorders that cause abnormal blood clotting. (Chen, 2014) Protein C deficiencies are more common than protein S deficiencies and affect 1 out of 300 people. (Chen, 2014) Protein S deficiencies are found in every 1 out of 20,000 people – making it a much more rare deficiency. (Chen, 2014) These deficiencies make themselves present and are “characterized by pain, redness, swelling, and tenderness in the affected areas.” (Protein Deficiencies Diseases) Complications as a result of these deficiencies may occur as childhood strokes, recurring miscarriages, recurrent clots in veins, and pulmonary embolism. (Chen, 2014) It is crucial for people who suffer from these protein deficiencies to avoid activities that can cause blood clotting or seek professional help by potentially going on a blood thinner.
Marasmus is a devastating and common deficiency seen in young, malnourished children. Marasmus is the “most common form of acute malnutrition in nutritional emergencies” and it can often lead to fatality. (Types of Undernutrition) Young children and infants who suffer from this deficiency try to conserve energy by reducing physical activity and their bodies reduce growth. (Types of Undernutrition) Because these children are not getting the nutrients or protein that they need, their bodies’ organs will begin to limit their function, which puts the children at extreme risk.
Malnourishment can also take on the form of extreme bloating and stomach swelling which is known as kwashiorkor. The swollen stomach is a result of fluid retention within the individual. (“Med-Health”) This form of malnourishment comes from a lack of proteins from carbohydrate sources and is more common in older children. (“Med-Health”) Clinical signs of kwashiorkor include (Types of Undernutrition):
- Loss of appetite
- Apathy and irritability
- Changes in hair color
Chen, Yi-Bin. "Congenital Protein C or S Deficiency: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine, 26 Nov. 2014. Web. 02 Nov. 2015. https://www.nlm.nih.gov/medlineplus/ency/article/000559.htm (Links to an external site.)
Tuso, Philip J., Mohamed H. Ismail, Benjamin P. Ha, and Carole Bartolotto. "Nutritional Update for Physicians: Plant-Based Diets." The Permanente Journal. The Permanente Journal, n.d. Web. 02 Nov. 2015. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3662288/#b33-permj17_2p0061 (Links to an external site.)
"Med-Health.net." Protein Deficiency Diseases. N.p., n.d. Web. 02 Nov. 2015. http://www.med-health.net/Protein-Deficiency-Diseases.html (Links to an external site.)
"Clinical Forms of Acute Malnutrition." Types of Undernutrition: Growth Failure -. UNICEF, n.d. Web. 02 Nov. 2015. http://www.unicef.org/nutrition/training/2.3/3.html (Links to an external site.)