The human body needs a balance of protein, fat, and carbohydrate to maintain health and vitality. When the body does not get enough food, undernutrition occurs. When the body does not get enough nutrients, malnutrition occurs. Both undernutrition and overnutrition can cause malnutrition . While deficiency in each macronutrient is problematic, protein deficiency is extremely dangerous and can cause protein-energy malnutrition (PEM) (Maleta K., 2006).
There are two types of protein-energy malnutrition: one is associated with protein deficiency in the absence of sufficient caloric intake, the other presents with both protein and energy deficiency. The main disorders associated with protein-energy malnutrition are kwashiorkor and marasmus syndrome. Kwashiorkor is caused by protein deficiency while marasmus is caused by energy deficiency. A third condition called marasmic kwashiorkor presents symptoms of both kwashiorkor and marasmus.
These diseases are prevalent in the developing world, where they affect mostly infants and children. They are also present in economically developed countries, where they affect food-insecure populations and the elderly, especially the hospitalized elderly. PEM can have secondary causes, namely chronic diseases such as chronic kidney disease, cancer cachexia, AIDS, and anorexia (Grover & Ee, 2009) (Merck Manuals, 2021).
The Dangers of Kwashiorkor & Marasmus
The severity of kwashiorkor and marasmus varies from subclinical deficiency to wasting syndrome to starvation. Adequate nutrition is necessary to combat both diseases, but, unfortunately, it is not enough to undo the metabolic damage done, especially with regards to stunted growth.
Kwashiorkor is caused by insufficient protein intake in the presence of sufficient calories. Sadly, this severe form of malnutrition is very common in developing countries, where infants and children do not get enough dietary protein. Certain African regions report kwashiorkor rates as high as 15% (WHOs Africa Nutrition Report Highlights an Increase in Malnutrition in Africa., 2021). Kwashiorkor has acute onset, and its main characteristic is edema. Edema usually starts in the legs, but it can spread to the entire body, including the abdomen and the face. Kwashiorkor is also usually accompanied by fatty liver, muscle wasting, loss of hair and decreased hair pigmentation, stunted growth, skin lesions, anemia, diarrhea, apathy and listlessness (NHS website, 2019).
Malnutrition & Portein Deficiency
Marasmus protein deficiency occurs when a person’s diet is deficient in both protein as well as calories. Marasmus starts generally immediately after birth. Infants affected by marasmus are slow to develop and present stunted growth, extremely low body weight, muscle wasting, depletion of adipose tissue, hypotension, and they suffer from repeated infections.
PEM conditions present also with deficiency of micronutrients, especially iron, iodine, zinc and vitamin A. According to Merk Manual the mortality rate in children affected by PEM varies from 5% to 40%. Severe PEM causes electrolyte imbalance, sepsis, heart failure, and hypothermia, which can lead to shock and death. Patients affected by kwashiorkor recover more rapidly than patients affected by marasmus.
As mentioned above, PEM therapy includes adequate nutrition; supportive care is considered on a case-to-case basis. Appetite stimulants are generally part of PEM therapy for patients affected by anorexia. Patients with cachexia can often be prescribed anabolic steroids or growth hormone. Refeeding syndrome is a complication of PEM therapy, which can be accompanied by hyperglycemia, diarrhea, fluid imbalance, and arrhythmias (Merck Manuals, 2021).
WHOs Africa Nutrition Report highlights an increase in malnutrition in Africa. (2021, September 1). WHO | Regional Office for Africa. https://www.afro.who.int/news/whos-africa-nutrition-report-highlights-increase-malnutrition-africa
Type-2 diabetes is a chronic metabolic condition that affects an estimated 425 million people worldwide. It is one of the biggest public health problems, and this already high number is estimated to surpass 600 million cases by 2045. Type-2 diabetes is a disease of lifestyle that affects the way the body metabolizes glucose. People who suffer from type-2 diabetes have either an inability to effectively utilize insulin or do not produce enough insulin to maintain a glucose level within the normal range of 70-100 mg/dL. Type-2 diabetes is also known as diabetes mellitus type2, noninsulin-dependent diabetes mellitus (NIDDM), and adult-onset diabetes. It used to be known as adult-onset diabetes because, formally, it was diagnosed in adults over the age of 45. Nowadays, unfortunately, type-2 diabetes is more and more prevalent in children as well, and, according to the National Diabetes Statistics Report, 193,000 children and teenagers under the age of 20 have been diagnosed with diabetes in 2015 (type-1 and type-2).
Healthy Blood Sugar Metabolism
In normal blood sugar metabolism, the beta cells of the pancreas produce and release insulin in response to the carbohydrate portion of a meal. Insulin is responsible for shuttling glucose away from the bloodstream and into liver and muscle cells. With repetitive excess glucose, cell receptor sites become resistant to insulin, causing glucose to remain in the bloodstream and build up to dangerously high levels. Therefore, type-2 diabetes is linked to insulin resistance. Additionally, as blood sugars remain elevated, the pancreas is forced to produce and release more insulin, which eventually puts a strain on the organ.
How Is Type 2 Diabetes Different From Type 1 & Gestational Diabetes?
There are two other types of diabetes: type-1 diabetes and gestational diabetes (GD). Type-1 diabetes is an auto immune disorder in which the beta cells of the pancreas are attacked and destroyed by the immune system. People with type-1 diabetes produce little to no insulin and become insulin-dependent for the rest of their lives. The damage is irreversible. Gestational diabetes only occurs in pregnancy. It affects 2 in 10 pregnant women, and it is generally diagnosed between the 24th and the 28th week of gestation. GD is caused by pregnancy hormones (namely, human placental lactogen) that cause the body to become insulin resistant.
It was originally thought that type-2 diabetes could not be cured and was genetic in nature. Medicine and nutrition are evolving sciences, and we now know that while there can be a genetic component to type-2 diabetes, it is mainly a disease of lifestyle. Risk factors may include family history, race (Black, Hispanics, American Indians, Asians Americans are at higher risk), age, low activity level, fat distribution (accumulation of abdominal fat), and body weight. Other medical conditions linked to developing type-2 diabetes are prediabetes, PCOS, and gestational diabetes. Women with gestational diabetes are at higher risk of developing the developing type-2 diabetes in their lifetime. Also, women who deliver babies weighing more than 4 kg have a higher risk of developing type-2 diabetes.
Symptoms Of Type 2 Diabetes
Symptoms of type-2 diabetes are unintended weight loss, increased thirst, frequent urination, increased hunger, fatigue, blurred vision, slow-healing sores, frequent infection, darkening of skin usually in the areas of the armpits and neck. Diabetes has serious long-term complication that are disabling and life-threatening. They range from stroke to heart disease, to high blood pressure and atherosclerosis, neuropathy, kidney damage, slow healing and infections, skin conditions (including bacterial and fungal infection), hearing impairment, sleep apnea, eye damage and blindness. In recent years, type-2 diabetes has been linked to increased risk of Alzheimer’s disease, which is now called by some type three diabetes.
Type-2 diabetes is diagnosed using the glycated hemoglobin (A1C) test. This test indicates average glucose levels for the past three months. Normal levels are below 5.7%. A result between 5.7 and 6.4% is considered prediabetes. A A1C result of 6.5% and above on two separate tests is considered diabetes. When A1C is not available, physicians may use a random glucose test, a fasting glucose test, or a glucose tolerance test. The latter is the preferred test used to check for gestational diabetes.
How Does Conventional Medicine Approach Type 2 Diabetes?
Conventional medical treatment is based on the use of medication to improve blood sugar control. Medications come with side effects and drug interactions. Most medications for type-2 diabetes are oral drugs while a few are injectable. Patients who are not able to manage their blood glucose through oral medications may require insulin injections as well. There are several classes of diabetes medications: alpha-glucosidase inhibitors aid in the breakdown of starches and sugars. Biguanides decrease intestinal absorption of glucose, help muscles absorb glucose, and decrease the amount of glucose that the liver makes. Metformin is a biguanide. This medication comes with a host of side effect which affect the gastrointestinal tract, including abdominal pain and diarrhea. Dopamine agonist is another type of medication, though its mechanism is still not understood. Dipeptidyl Peptidase-4 inhibitors (DPP-4) help the pancreas make more insulin, and they also reduce blood sugar without causing hypoglycemia. Glucagon-like peptide 1 receptor agonists (GLP-1) mimic the natural hormone incretin by stimulating the growth of beta cells and decreasing appetite. GLP-1 receptor agonists also influence glucagon utilization. Meglitinides help the body release insulin, though they may cause hypoglycemia and need to be prescribe with caution. Sodium-glucose cotransporter-2 inhibitors (SGLT 2) prevent the kidneys from holding onto glucose and promote glucose excretion through urine. Sulfonylureas stimulate pancreatic insulin production. Thiazolidinediones help fat tissue utilize insulin more efficiently, and they decrease glucose in the liver.
It is important to note that people suffering from type-2 diabetes also are often affected by other conditions like heart disease, high blood pressure or high cholesterol, and, therefore, the choice of medication(s) for treatment of type-2 diabetes must be based on the patient’s complete clinical picture. For example, GLP-1 receptor agonists are usually preferred for diabetes patients affected by cardiovascular disease, heart failure or chronic kidney disease. As stated above, these medications come with side effects. They also cause depletion. For example, medication like glyburide, glipizide, and chlorpropamide deplete CoQ10, while metformin depletes vitamin B12.
Nutrients That May Be Linked To Type 2 Diabetes
Nutrients that are linked to the development of type-2 diabetes, or are found in insufficient levels in people suffering from a type-2 diabetes, are vitamin A, magnesium, vitamin D and chromium. Vitamin A boosts beta cell activity, and new research points to vitamin A insufficiency as playing a role in developing type-2 diabetes. Low magnesium levels, both intracellular and extracellular, are generally associated with type-2 diabetes. Insulin and glucose are important for magnesium metabolism, and magnesium has a key role in regulating insulin action, glucose uptake, and vascular tone. Studies confirm that low vitamin D level is a risk factor for type-2 diabetes. Low vitamin D is linked to beta cell disfunction, insulin resistance, and systemic inflammation all of which can contribute to type-2 diabetes. Chromium is an essential trace mineral important for insulin regulation as well as for carbohydrate and lipid metabolism. Supplementation with chromium picolinate has been shown to reduce insulin resistance and to lower risk of cardiovascular disease and type-2 diabetes.
What Happened To Diabetics Before Injectable Insulin?
Before the advent of diabetes medication and injectable insulin the treatment of choice was a reduced carbohydrate diet. For decades, after the introduction of drugs, the medical establishment would prescribe a low-fat diet comprised of at least 40% to 50% of carbohydrates. However, the past few years have seen a shift in the nutrition therapy treatment proposed by the medical community. New evidence-based approaches are being developed, and different diets like the low carbohydrate diet and the Mediterranean diet are being researched. The goal of nutrition therapy for the management of type-2 diabetes should focus on promoting healthy eating, stabilizing glucose levels, lowering lipid levels and blood pressure, and promoting weight loss. This needs to be done in a manner that feels achievable by the patient and can be sustainable in the long-term.
In 2013, the American Diabetes Association created a list of recommendations and interventions focused on nutrition therapy which include reduced calorie diet, carbohydrate counting, simplified meal plans, fat intake, healthy food or exchange choices, behavioral strategies, and physical activity. The most recent nutritional guidelines from the ADA conclude that there is no ideal macronutrient ratio for all people suffering from type-2 diabetes and that recommendations need to be individually tailored to each patient’s clinical picture and goal(s). The ADA recommends that patients receive individualized nutrition therapy and work with a nutritionist or registered dietitian specializing in nutrition therapy for diabetes. This new approach has lead researchers to perform studies on the outcomes of several diets. One of the most studied diets has been the Mediterranean diet.
The Mediterranean Diet & Type 2 Diabetes
The Mediterranean diet is rich in functional foods that have active ingredients associated with the management and prevention of diseases like type-2 diabetes. Regular consumption of such functional foods has been associated with reduced cholesterol levels, lower inflammation, and enhanced insulin sensitivity, all factors necessary to prevent and manage type-2 diabetes. The functional foods that are key components of the Mediterranean diet are fruits, vegetables, oily fish, olive oil, tree nuts, and legumes. These foods contain phytochemicals that have been shown to have anti-inflammatory and antioxidant properties as well as beneficial effects on glucose metabolism and the cardiovascular system. It is also interesting to note that exercise seems to enhance the beneficial effect of these functional foods.
Current research also points towards lower carbohydrate diets as being effective for the management of type-2 diabetes. Low carbohydrate diets focus on high vegetable intake, moderate to high protein intake, moderate to high fat intake while restricting the intake of carbohydrates to fruits, whole grains and legumes.
Regardless of the type of diet prescribed, patients suffering from type-2 diabetes should practice calorie deficit through portion control to aid in weight loss which has been proven to be the best tool to manage hemoglobin A1C levels.
How Does Age Affect Risk Factor In The Development of Type 2 Diabetes?
Age is also an important risk factors for the development of diabetes, and one that we must take into consideration when choosing nutrition therapy for type-2 diabetics. While childhood diabetes has reached epidemic proportions in this country, most people diagnosed with type-2 diabetes are diagnosed after the age of 45. Once condition that is associated with age and affects an estimated 43% of men and 26% of women is sarcopenia. Sarcopenia is characterized by a progressive loss of muscle mass and strength at the rate of 3% to 8% per decade. Muscle tissue is an important site for glycogen storage, and it has an important role in glucose metabolism. Therefore, loss of muscle mass negatively impacts glucose management as sarcopenia greatly reduces glycogen storage capacity.
High Protein Diets And Metabolic Disease
Historically, high protein diets have always been feared for patients with metabolic diseases because of the detrimental effect protein could have on kidney function. A recent meta-analysis conducted by Devries et al. indicated that high protein diets (1.5 g per kilogram of body weight) does not negatively impact kidney function on glomerular filtration rate in adults without kidney disease. In the past, it was also thought that excess protein would raise glucose levels through gluconeogenesis process. However, these findings have been discredited by several studies which have proven that gluconeogenesis is a demand- driven process.
New evidence advocates for consumption of higher protein by healthy older adults (1.0-1.2 g/kg/day) to preserve muscle mass and function. Older adults who are malnourished or at risk of malnutrition are recommended even higher amounts (1.2-1.5 g/kg/day). Improving muscle mass and physical performance in older population will directly improve management of type-2 diabetes. One study compared hypocaloric high protein diets versus high carbohydrate diets in older adults with sarcopenia. The researchers found that both diet had similar effects on the total amount of weight lost, but the high protein diet improved insulin sensitivity and preserved lean body mass while the high carbohydrate diet did not. Another study compared a high protein diet with a standard protein diet; the high protein diet induced a greater reduction in fat mass in men and women with type-2 diabetes. While glycemic control improved similarly in all groups, the change in insulin concentration was related to the extent of fat mass lost. This suggests that the higher protein diet may have a more favorable effect on glycemic control than a standard protein diet.
While dietary changes are foundational to the management of type-2 diabetes, behavioral modification cannot be discounted. It is human nature to be resistant to change, and we cannot underestimate the emotional and psychological importance of food. For these reasons, dietary modifications need to be sustainable in the long term. Emphasis needs to be placed on patient education and support so that the new dietary habits are not abandoned at the first obstacle.
Nutritionists and dietitians working with diabetes patients need to work closely with their physicians as well so that medications can be promptly adjusted accordingly. I worked extensively with type-2 diabetes clients, and I am always shocked by the number of people who come to me who are on several medications but do not test their blood sugar regularly. In my practice I do not work with clients who refuse to wear a continuous glucose monitor or refuse to monitor their blood sugar levels several times a day via finger prick.
Weight loss is important for overweight and obese people suffering from type-2 diabetes. Losing weight improves glycemic control and decreases fasting blood sugar concentrations; it can improve insulin action and reduce the need for medication. A meta-analysis of gastric bypass patients showed that more than 2/3 of extremely obese patients with type-2 diabetes who underwent gastric bypass surgery had normalized glycemic control after losing at least 30% of their bodyweight. Patients with severe pancreatic beta cell dysfunction may not be as responsive to weight loss as those with less extensive disease.
Complimentary and Alternative Medicine Treatment of Type 2 Diabetes
Complementary and alternative medicine can be used successfully as adjuvant therapy for the treatment of diabetes. The most common used CAM for type-2 diabetes includes herbal medicine and nutriceuticals, acupuncture, chiropractic adjustments and meditation. Alpha-lipoic acid (ALA) is an antioxidant found in organ meats and dark leafy greens which can lower blood sugar and help prevent or reduce neuropathy. Chromium is a trace mineral found in vegetables and whole grains that helps with glucose metabolism. Cinnamon decreases glucose uptake from the G.I. tract, similar to alpha-glucosidase inhibitors medications. Preliminary studies show that antioxidants found in foods like olive oil, dark chocolate and green tea can lower blood sugar and cholesterol, but more research is needed. Ginseng has been used for hundreds of years by certain cultures as a blood sugar remedy. Practitioners must be cautious when using herbs and supplements in clients who take diabetes medication: always check for drug-herb and drug-nutrient interactions before recommending CAM.
Acupuncture is helpful in reducing the pain associated with peripheral neuropathy. Chiropractic care can help stabilize glucose levels by removing spine misalignment, which ameliorates central nervous system communication and can improve pancreatic function.
Lastly, there is increasing evidence that epigenetics plays a role in the metabolic programming of the fetus. While more research is needed to fully understand epigenetic expression and its relation to the disease, we know that maternal and paternal nutrition can cause genetic dysregulation associated with several components that contribute to type-2 diabetes risk. This might be the reason why children born to mothers affected by gestational diabetes have a higher incidence of type-2 diabetes later in life.
While the medical underpinnings of diabetes are well understood, medications alone cannot reverse type-2 diabetes. Lifestyle and dietary changes should be the primary focus in addressing this metabolic disease. CAM are crucial components in any treatment plan and should have greater prominence in how Western medicine approaches type-2 diabetes.
Type 2 diabetes – Symptoms and causes [Internet]. Mayo Clinic. [cited 2020 Dec 2]. Available from: https://www.mayoclinic.org/diseases-conditions/type-2-diabetes/symptoms-causes/syc-20351193
Gray A, Threlkeld RJ. Nutritional recommendations for individuals with diabetes. In: Feingold KR, Anawalt B, Boyce A, Chrousos G, de Herder WW, Dungan K, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000 [cited 2020 Dec 1]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK279012/
Gestational diabetes: medlineplus genetics [Internet]. [cited 2020 Dec 3]. Available from: https://medlineplus.gov/genetics/condition/gestational-diabetes/
Ong TP, Ozanne SE. Developmental programming of type 2 diabetes: early nutrition and epigenetic mechanisms. Current Opinion in Clinical Nutrition and Metabolic Care. 2015 Jul;18(4):354–60.
Trasino SE, Benoit YD, Gudas LJ. Vitamin a deficiency causes hyperglycemia and loss of pancreatic β-cell mass. J Biol Chem. 2014 Dec 1;jbc.M114.616763.
Barbagallo M, Dominguez LJ. Magnesium and type 2 diabetes. World J Diabetes. 2015 Aug 25;6(10):1152–7.
Xuan Y, Zhao H, Liu J-M. Vitamin D and type 2 diabetes mellitus (D2). J Diabetes. 2013 Sep;5(3):261–7.
A scientific review: the role of chromium in insulin resistance. Diabetes Educ. 2004;Suppl:2–14.
Biessels GJ, Kappelle LJ, Utrecht Diabetic Encephalopathy Study Group. Increased risk of Alzheimer’s disease in Type II diabetes: insulin resistance of the brain or insulin-induced amyloid pathology? Biochem Soc Trans. 2005;33(Pt 5):1041–4.
Westman EC, Yancy WS Jr., Humphreys M. Dietary treatment of diabetes mellitus in the pre-insulin era (1914-1922). Perspect Biol Med2006;49:77 83. doi:10.1353/pbm.2006.0017 pmid:16489278
Wheeler ML, Dunbar SA, Jaacks LM, et al. Macronutrients, food groups, and eating patterns in the management of diabetes: a systematic review of the literature, 2010. Diabetes Care2012;35:434-45. doi:10.2337/dc11-2216 pmid:22275443
Franz MJ, Boucher JL, Evert AB. Evidence-based diabetes nutrition therapy recommendations are effective: the key is individualization. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy. 2014;7:65.
Nguyen NT, Nguyen X-MT, Lane J, Wang P. Relationship between obesity and diabetes in a us adult population: findings from the national health and nutrition examination survey, 1999–2006. OBES SURG. 2011 Mar 1;21(3):351–5.
Ley SH, Hamdy O, Mohan V, Hu FB. Prevention and management of type 2 diabetes: dietary components and nutritional strategies. The Lancet. 2014 Jun 7;383(9933):1999–2007.
Lindström J, Absetz P, Hemiö K, Peltomäki P, Peltonen M. Reducing the risk of type 2 diabetes with nutrition and physical activity – efficacy and implementation of lifestyle interventions in Finland. Public Health Nutrition. 2010 Jun;13(6A):993–9.
Klein S, Sheard NF, Pi-Sunyer X, Daly A, Wylie-Rosett J, Kulkarni K, et al. Weight management through lifestyle modification for the prevention and management of type 2 diabetes: rationale and strategies. A statement of the american diabetes association, the north american association for the study of obesity, and the american society for clinical nutrition. Am J Clin Nutr. 2004 Aug 1;80(2):257–63.
Salas-Salvadó J, Bulló M, Babio N, Martínez-González MÁ, Ibarrola-Jurado N, Basora J, et al. Reduction in the incidence of type 2 diabetes with the mediterranean diet: results of the predimed-reus nutrition intervention randomized trial. Diabetes Care. 2011 Jan 1;34(1):14–9.
Beaudry KM, Devries MC. Nutritional strategies to combat type 2 diabetes in aging adults: the importance of protein. Front Nutr [Internet]. 2019 [cited 2020 Dec 1];6. Available from: https://www.frontiersin.org/articles/10.3389/fnut.2019.00138/full
McCarty MF. Toward a wholly nutritional therapy for type 2 diabetes. Medical Hypotheses. 2000 Mar 1;54(3):483–7.
Forouhi NG, Misra A, Mohan V, Taylor R, Yancy W. Dietary and nutritional approaches for prevention and management of type 2 diabetes. BMJ [Internet]. 2018 Jun 13 [cited 2020 Dec 1];361. Available from: https://www.bmj.com/content/361/bmj.k2234
Pharmavite. Common drug classes, drug-nutrient depletions, & drug-nutrient interactions. www.aafp.org/dam/AAFP/documents/about_us/sponsored_resources/Nature%20Made%20Handout.pdf. Accessed September 20, 2019.
Rhee TG, Westberg SM, Harris IM. Use of complementary and alternative medicine in older adults with diabetes. Diabetes Care [Internet]. 2018 Apr 10 [cited 2020 Dec 2]; Available from: https://care.diabetesjournals.org/content/early/2018/04/10/dc17-0682
Complementary and alternative medicine for diabetes – health encyclopedia – university of rochester medical center [Internet]. [cited 2020 Dec 1]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=134&ContentID=166
Grundy SM. Dietary therapy in diabetes mellitus. Is there a single best diet? Diabetes Care. 1991 Sep;14(9):796–801.
Alkhatib A, Tsang C, Tiss A, Bahorun T, Arefanian H, Barake R, et al. Functional foods and lifestyle approaches for diabetes prevention and management. Nutrients [Internet]. 2017 Dec 1 [cited 2020 Dec 1];9(12). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5748760/
Proteins differ greatly in their nutritive value, and there are numerous methods used in nutrition science to establish protein quality and bio-availability. Protein quality refers to a protein’s digestibility as well as its amino acid profile and how well the protein is used by the body to perform specific metabolic functions. One way that protein quality can be evaluated is by categorizing proteins as complete (also referred to as high-quality) or incomplete (also referred to as low-quality). Complete proteins contain all the essential amino acids that the body requires from food whereas incomplete proteins lack one or more of the essential amino acids.
Methods To Evaluate Protein Quality
Different methods are used to evaluate protein quality: biological value (BV) and net protein utilization are two of them. These methods not only look at a food’s protein profile, but they also look at how the body utilizes the protein in a specific food. Biological value is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism’s body. BV uses nitrogen to establish how readily the digested protein can be used in protein synthesis. Proteins are the major source of nitrogen in our diet, and BV assumes protein to be the only source of nitrogen. The difference between the amount of nitrogen ingested and the amount of nitrogen excreted tells us how much nitrogen has been incorporated in an organism’s body. The ratio of nitrogen incorporated into the body over nitrogen absorbed gives the biological value. Unlike other measures of protein usability, BV does not consider how readily the protein can be digested and absorbed.
What Is Net Protein Utilization?
Net protein utilization (NPU) also estimates nitrogen retention. Unlike BV, though, this method estimates nitrogen retention by determining the difference between body nitrogen content of animals fed no protein and those fed a test protein. This value divided by the amount of protein consumed is the NPU, which is defined as the “percentage of the dietary protein retained”. While both NPU and BV estimate retained nitrogen, in the calculation of NPU the denominator is the total protein eaten whereas in the calculation of BV it is the amount absorbed.
Protein and Kidney Health As Used In Nutritional Science
Biological value and net protein utilization are commonly used in nutrition science as a guideline for protein choice in diseased states that need to restrict protein intake. Kidney disease is one of these conditions. People suffering from kidney disease need to restrict protein intake. Eliminating protein altogether is not an option, as protein malnutrition would cause even more harm. Therefore, people suffering from kidney disease need to focus on protein foods of high biological value that the body can metabolize efficiently and that yield very little waste. The diet of a person suffering from kidney disease not in dialysis needs to provide around 0.6 to 0.8g per kg of body weight of proteins. At least 50% of proteins needs to be of high biological value (eggs, meat and poultry, fish, and dairy). People on dialysis have higher protein needs that those who are not on dialysis; therefore, patients on peritoneal dialysis need 1.3g per kg of body weight; patients in hemodialysis are recommended 1.2g per kg of body weight.
Sarwar G, Blair R, Friedman M, Gumbmann MR, Hackler LR, Pellett PL, et al. Inter- and Intra-laboratory Variability in Rat Growth Assays for Estimating Protein Quality of Foods. Journal of AOAC INTERNATIONAL. 1984 Sep 1;67(5):976–81
Stipanuk MH, Caudill MA, editors. Biochemical, physiological, and molecular aspects of human nutrition. 4th ed. St. Louis, Mo: Elsevier; 2019. 959 p.