9.2 Protein-Energy Malnutrition Assessment
4 min read•july 30, 2024
Protein-energy malnutrition (PEM) is a serious form of undernutrition that can affect people of all ages, but especially young children. It's caused by not getting enough protein and calories, leading to wasting, stunted growth, and weakened immunity.
Assessing PEM involves measuring body size, composition, and biochemical markers. Key indicators include weight-for-age, height-for-age, and mid-upper arm circumference. Blood tests for proteins like albumin and prealbumin can also show nutritional status at the cellular level.
Protein-energy malnutrition: Pathophysiology
Definition and Causes
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- Protein-energy malnutrition (PEM) is a form of undernutrition resulting from chronic deficiency of protein and energy. It is most common in young children but can impact all age groups.
- Primary PEM is caused by inadequate intake of protein and calories (poverty, food insecurity, poor feeding practices)
- Secondary PEM occurs due to nutrient malabsorption (intestinal disorders), impaired utilization (metabolic diseases), or increased requirements (burns, infections, trauma)
Clinical Forms and Manifestations
- is a severe form of PEM characterized by wasting and depletion of subcutaneous fat and muscle. It typically occurs in the first year of life.
- is a severe form of PEM characterized by , fatty liver, skin lesions (flaky paint dermatosis), and hair changes (sparse, thin, reddish). It typically manifests in older children.
- PEM impairs cellular growth and function, weakens the immune system, delays wound healing, and leads to loss of muscle mass and subcutaneous fat.
- Prolonged PEM can result in stunted growth (short stature), impaired cognitive development (lower IQ scores), increased risk of infections (pneumonia, diarrhea), and organ damage (liver, heart, kidneys).
Anthropometry for malnutrition identification
Body Size and Composition Measurements
- Anthropometry involves taking body measurements to assess nutritional status and identify PEM. Key measurements include weight, height/length, head circumference, , and skinfold thickness.
- Low weight-for-age (underweight) is an indicator of acute and/or chronic PEM. It is defined as weight-for-age < -2 standard deviations (SD) of the WHO Child Growth Standards median.
- Low height/length-for-age (stunting) reflects chronic PEM. It is defined as height/length-for-age < -2 SD of the WHO Child Growth Standards median.
- Low weight-for-height/length (wasting) indicates acute PEM. It is defined as weight-for-height/length < -2 SD of the WHO Child Growth Standards median. Severe wasting is < -3 SD.
- MUAC is a simple screening tool for PEM. MUAC < 11.5 cm (severe), 11.5-12.5 cm (moderate), > 12.5 cm (mild/normal). It is useful for children aged 6-59 months.
Body Fat and Muscle Assessments
- Triceps skinfold thickness < 3rd percentile for age and sex suggests PEM and depletion of fat stores. Other skinfold sites (subscapular, suprailiac) may also be measured.
- BMI-for-age is used to screen for PEM in children and adolescents aged 5-19 years. BMI-for-age < -2 SD indicates thinness (PEM).
- Arm muscle area (AMA) estimates skeletal muscle mass using MUAC and triceps skinfold. AMA < 5th percentile indicates .
- Bioelectrical impedance analysis (BIA) measures body composition based on electrical conductivity of tissues. Low phase angle suggests cell membrane integrity loss and malnutrition.
Biochemical markers of protein-energy status
Serum Proteins
- Biochemical markers provide objective measures of protein and energy status at the cellular level. They are used in conjunction with anthropometric and dietary data.
- Serum albumin is the most abundant plasma protein and reflects protein status over the previous 14-20 days. Levels < 3.5 g/dL suggest protein depletion.
- Serum prealbumin (transthyretin) has a shorter half-life than albumin and is a more sensitive indicator of recent protein intake. Levels < 15 mg/dL indicate .
- Serum transferrin is a transport protein for iron. Levels < 200 mg/dL may indicate protein depletion, but it is also affected by iron status.
- Serum retinol-binding protein (RBP) transports vitamin A and has a short half-life. Levels < 2.6 mg/dL suggest protein deficiency.
Functional and Metabolic Indicators
- Total lymphocyte count (TLC) assesses immune function and protein status. TLC < 1200 cells/mm3 indicates protein depletion and impaired immunity.
- Nitrogen balance studies compare nitrogen intake (from protein) to nitrogen excretion (urine, feces, sweat). Negative nitrogen balance indicates protein catabolism and malnutrition.
- Creatinine-height index (CHI) estimates muscle mass based on 24-hour urinary creatinine excretion. CHI < 60% of standard suggests protein malnutrition.
- Insulin-like growth factor-1 (IGF-1) mediates growth hormone action. Low IGF-1 levels reflect chronic undernutrition and growth impairment.
Dietary adequacy for malnutrition prevention
Protein and Energy Requirements
- Dietary assessment methods such as 24-hour recalls, food frequency questionnaires, and food records are used to evaluate protein and energy intake.
- Protein requirements vary by age, sex, body size, and physiological state. The Recommended Dietary Allowance (RDA) for protein is 0.8 g/kg/day for adults, 1.2-2.0 g/kg/day for children, and up to 1.5 g/kg/day for pregnant/lactating women.
- Energy requirements depend on age, sex, body size, physical activity level, and health status. The Estimated Energy Requirement (EER) equations predict energy needs based on these factors.
- Inadequate energy intake leads to use of protein for energy, reducing its availability for growth and maintenance. Protein sparing occurs when sufficient calories are provided.
Protein Quality and Diet Diversity
- Protein quality is determined by digestibility and amino acid composition. High-quality, complete proteins (eggs, meat, fish, dairy, soy) contain all essential amino acids. Lower-quality, incomplete proteins (most plant proteins) are limited in one or more essential amino acids.
- Protein-energy ratio (P/E ratio) is the proportion of protein to total energy in the diet. A P/E ratio of 0.06-0.08 (6-8% of calories from protein) is considered adequate for most healthy individuals. Higher ratios may be needed for catch-up growth, wound healing, or other catabolic states.
- Dietary diversity scores and minimum acceptable diet indicators assess diet quality and micronutrient adequacy, which are important for preventing PEM in developing countries.
- Complementary feeding practices (timely introduction of solid foods, meal frequency, nutrient density) are critical for preventing PEM in infants and young children.
Key Terms to Review (17)
Academy of Nutrition and Dietetics Standards: The Academy of Nutrition and Dietetics Standards are a set of guidelines and criteria established to ensure the quality and effectiveness of nutrition services delivered by registered dietitian nutritionists (RDNs). These standards encompass various aspects of practice, including ethical behavior, competence, and professional development, ensuring that RDNs provide evidence-based care in the assessment and management of nutritional needs, including those related to protein-energy malnutrition.
Anthropometric measurements: Anthropometric measurements are quantitative assessments of the physical dimensions and composition of the human body, typically including parameters like height, weight, body mass index (BMI), and circumferences of various body parts. These measurements are essential for evaluating growth, health status, and nutritional needs, serving as vital tools in clinical nutrition, public health, and individual dietary assessments.
Biochemical analysis: Biochemical analysis refers to the laboratory techniques used to measure and evaluate biochemical markers in biological samples, which provide valuable insights into an individual's nutritional status and metabolic processes. This analysis helps in identifying deficiencies or imbalances in nutrients, which is crucial for accurate nutrition assessment, diagnosis of conditions like protein-energy malnutrition, and monitoring of nutritional progress over time.
Body Mass Index (BMI): Body Mass Index (BMI) is a numerical value derived from an individual's weight and height, calculated by dividing weight in kilograms by the square of height in meters. BMI is commonly used as a screening tool to categorize individuals into weight status categories, which can help in assessing overall health and risk for certain conditions. It serves as an important indicator in evaluating micronutrient deficiencies, nutritional assessments in healthcare, and monitoring nutritional progress.
Edema: Edema is the medical term for swelling caused by excess fluid trapped in the body’s tissues. It can occur in any part of the body but is most commonly noticed in the extremities, such as the legs, ankles, and feet. Understanding edema is crucial as it can indicate underlying health issues, including malnutrition or imbalances in protein levels, which are important when assessing a person's nutritional status.
Energy deficit: Energy deficit occurs when the number of calories consumed is less than the number of calories expended by the body. This state can lead to weight loss and, in severe cases, protein-energy malnutrition, as the body starts to use its own tissues for energy. Understanding energy deficit is crucial in assessing nutritional status and planning dietary interventions, especially in populations at risk of malnutrition.
Kwashiorkor: Kwashiorkor is a severe form of protein-energy malnutrition that primarily affects children, characterized by edema, irritability, and an enlarged abdomen. It occurs when there is inadequate protein intake despite sufficient calorie consumption, leading to imbalances in essential nutrients and resulting in various physiological disturbances.
Marasmus: Marasmus is a severe form of malnutrition characterized by inadequate intake of protein and calories, leading to significant weight loss and muscle wasting. This condition typically arises in infants and young children, resulting in a noticeable depletion of body fat and protein stores, which impacts growth and overall health. Recognizing marasmus is crucial, as it can have long-lasting effects on development and survival if not addressed promptly.
Mid-upper arm circumference (muac): Mid-upper arm circumference (MUAC) is a measurement taken around the midpoint of the upper arm, typically used to assess nutritional status, particularly in the context of protein-energy malnutrition. This simple and quick anthropometric measurement helps identify individuals who are malnourished or at risk of malnutrition, especially in vulnerable populations such as children and pregnant women.
Mini Nutritional Assessment (MNA): The Mini Nutritional Assessment (MNA) is a validated screening tool designed to assess the nutritional status of older adults, specifically to identify those at risk of malnutrition. This tool consists of a combination of anthropometric measurements, dietary assessments, and subjective questions about health and lifestyle, making it particularly useful for healthcare professionals in evaluating protein-energy malnutrition among seniors.
Muscle wasting: Muscle wasting, also known as muscle atrophy, refers to the loss of muscle mass and strength due to various factors such as malnutrition, illness, or lack of physical activity. This condition is significant in assessing an individual's nutritional status and overall health, particularly in the context of physical examination techniques, identifying malnutrition, and assessing protein-energy malnutrition.
Nutritional supplementation: Nutritional supplementation refers to the process of providing additional nutrients, either in the form of dietary supplements or fortified foods, to enhance an individual's nutritional intake. This practice is especially crucial in managing conditions like protein-energy malnutrition, where specific nutrient deficits can lead to severe health issues. By supplying essential vitamins, minerals, proteins, or calories, nutritional supplementation helps improve overall health and recovery in individuals facing malnutrition.
Protein deficiency: Protein deficiency occurs when an individual does not consume enough protein to meet their body's needs for growth, repair, and maintenance of tissues. This condition can lead to various health issues, particularly in vulnerable populations like children and the elderly, and is a key component of protein-energy malnutrition, which combines inadequate protein and calorie intake.
Therapeutic feeding: Therapeutic feeding is a specialized nutritional intervention designed to treat and prevent malnutrition, especially in individuals suffering from protein-energy malnutrition. This approach often includes the use of energy-dense, nutrient-rich foods or formulas aimed at rapidly restoring health and promoting recovery in vulnerable populations, such as children and those with chronic illnesses. Effective therapeutic feeding is critical in addressing the immediate nutritional needs while also focusing on the underlying causes of malnutrition.
Undernourished: Undernourished refers to a state where an individual's dietary intake does not meet their nutritional needs, leading to deficiencies in energy and essential nutrients. This condition can result in impaired growth, weakened immune function, and increased susceptibility to diseases, making it a critical issue in assessing protein-energy malnutrition.
Vulnerable populations: Vulnerable populations are groups of individuals who are at a higher risk for adverse health outcomes due to various factors, including socio-economic status, age, disability, and lack of access to healthcare. These populations often face barriers that limit their ability to obtain adequate nutrition and healthcare, making them particularly susceptible to conditions such as protein-energy malnutrition. Addressing the needs of these groups is crucial in ensuring equitable health outcomes and improving overall community well-being.
World Health Organization (WHO) Guidelines: World Health Organization (WHO) Guidelines are evidence-based recommendations developed by the WHO to inform health policies and practices globally. These guidelines aim to improve health outcomes and are particularly important for assessing and addressing issues such as protein-energy malnutrition, which can have profound effects on populations, especially in vulnerable groups such as children and the elderly.