Malnutrition is an acute problem of the 21st century

Malnutrition is a form of malnutrition. Malnutrition may result from inadequate nutrient intake, malabsorption, abnormal metabolism, nutrient loss through diarrhea, or increased nutritional requirements (as occurs with cancer or infection).

Malnutrition progresses gradually; each stage usually takes a long time to develop. First, nutrient levels in the blood and tissues change, then intracellular changes in biochemical function and structure occur. Eventually, signs and symptoms appear.

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Risk factors for malnutrition

Undernutrition is associated with many disorders and circumstances, including poverty and social adversity. The risk of its occurrence is also greater at certain times (infancy, early childhood, adolescence, pregnancy, breastfeeding, old age).

Infancy and Childhood. Infants and children are particularly susceptible to nutritional deficiencies because of their high energy and essential nutrient requirements. Newborns with vitamin K deficiency may develop hemorrhagic disease of the newborn, a life-threatening disorder. An exclusively breastfed infant may develop vitamin B12 deficiency _if the mother is a strict vegetarian. Undernourished infants and children are at risk for protein-energy malnutrition, iron deficiency, folate deficiency, vitamin A deficiency, vitamin C deficiency, copper deficiency, and zinc deficiency. During puberty, nutritional requirements increase because the rate of overall growth accelerates. Malnutrition in girls and young women may be due to the neurogenic anorexia nervosa that characterizes them.

Pregnancy and lactation. Nutrient requirements increase during pregnancy and lactation. Deviations from the normal diet may occur during pregnancy, including pica (consumption of non-nutritive substances such as clay and activated charcoal). Iron deficiency anemia is quite common, as is folate deficiency anemia, especially among women who have taken oral contraceptives.

Old age. Aging, even in the absence of disease or nutritional deficiency, results in sarcopenia (progressive loss of lean body mass), beginning after age 40 and ultimately resulting in a loss of approximately 10 kg (22 lb) of lean mass in men and 5 kg (11 lb) in women. The causes include decreased physical activity and food intake and increased cytokine levels (especially interleukin-6). In men, sarcopenia is also caused by decreased androgen levels. With aging, basal metabolic rate (primarily due to a decrease in lean body mass), total body weight, height, and skeletal mass decrease and mean fat mass (as a percentage of body mass) increases by approximately 20–30% in men and 27–40% in women.

From the age of 20 to 80, food intake decreases, especially in men. Anorexia due to the aging process itself has many causes: adaptive relaxation of the fundus of the stomach decreases, secretion and activity of cholecystokinin, which causes a feeling of satiety, increases, and the release of leptin (an anorexic hormone produced by adipocytes) increases. Reduced sense of smell and taste reduce the pleasure of eating, but usually only slightly reduce the amount of food consumed. Anorexia can have other causes (for example, loneliness, inability to buy food and prepare food, dementia, some chronic disorders, use of certain drugs). A typical cause of malnutrition is depression. Sometimes neurogenic anorexia, paranoia or manic states interfere with eating. Dental problems limit the ability to chew and subsequently digest and assimilate food. Difficulty swallowing (eg, due to seizures, strokes, other neurological disorders, esophageal candidiasis, or xerostomia) is also a common cause. Poverty or functional impairment limits access to nutrient intake.

People in nursing homes are particularly at risk of developing protein-energy malnutrition syndrome (PEMS). They are often disoriented and unable to express that they are hungry or what foods they prefer. They may be physically unable to feed themselves. They may be very slow at chewing or swallowing, and it may be tedious for another person to feed them enough food. Insufficient intake and absorption of vitamin D, as well as insufficient sun exposure, lead to osteomalacia.

Various disorders and medical procedures. Diabetes, some chronic GI disorders, bowel resections, and some other GI surgeries lead to impaired absorption of fat-soluble vitamins, vitamin B, calcium, and iron. Celiac disease, pancreatic insufficiency, or other disorders may lead to malabsorption. Decreased absorption may contribute to iron deficiency and osteoporosis. Liver disease impairs the accumulation of vitamins A and B, and interferes with the metabolism of protein and energy sources. Renal failure predisposes to deficiencies of protein, iron, and vitamin D. Inadequate food intake may result in anorexia in patients with cancer, depression, and AIDS. Infections, trauma, hyperthyroidism, extensive burns, and prolonged fever increase metabolic demands.

Vegetarian diets. Iron deficiency can occur in "egg-and-milk" vegetarians (although such a diet can be a guarantee of good health). Strict vegetarians can develop vitamin B ₁₂ deficiency if they do not consume yeast extracts or Asian-style fermented foods. They also have reduced intake of calcium, iron, and zinc. A fruit-only diet is not recommended because it is deficient in protein, Na, and many micronutrients.

Fad diets. Some fad diets lead to vitamin, mineral and protein deficiencies, heart, kidney and metabolic disorders and sometimes death. Very low-calorie diets (<400 kcal/day) cannot maintain health over the long term.

Medicines and dietary supplements. Many drugs (eg, appetite suppressants, digoxin) decrease appetite, while others impair nutrient absorption or metabolism. Some drugs (eg, appetite stimulants) have catabolic effects. Certain drugs can impair the absorption of many nutrients; for example, anticonvulsants can impair the absorption of vitamins.

Alcohol or drug dependence. Patients with alcohol or drug dependence may neglect their nutritional needs. Absorption and metabolism of nutrients may also be impaired. Intravenous drug users commonly become malnourished, as do alcoholics who consume more than one liter of hard liquor per day. Alcoholism can cause deficiencies in magnesium, zinc, and certain vitamins, including thiamine.

Symptoms of Malnutrition

Symptoms vary depending on the cause and type of nutritional deficiency.

The diagnosis is based on the results of both the medical history and diet, physical examination, body composition analysis and selective laboratory tests.

History. The history should include questions about food intake, recent changes in weight, and risk factors for malnutrition, including medication and alcohol use. Unintentional loss of more than 10% of usual weight over three months indicates a high probability of malnutrition. Social history should include questions about whether money is available for food and whether the patient can buy and prepare food.

When examining a patient by organs and systems, it is necessary to focus on symptoms of nutritional deficiency. For example, headache, nausea, and diplopia may indicate vitamin A intoxication.

Physical examination. Physical examination should include measurement of height and weight, fat distribution, and anthropometric determination of lean body mass. Body mass index [BMI = weight (kg)/height (m)] adjusts weight for height. If the patient's weight is <80% predicted for height or if the BMI is <18, malnutrition should be suspected. Although these findings are helpful in diagnosing malnutrition, they are of little specificity.

The area of the muscle region of the middle upper forearm is used to estimate the muscle mass of the body. This area is calculated based on the triceps skin fold thickness (TSF) and the circumference of the middle forearm. Both measurements are taken on the same site, with the patient's right arm in a relaxed position. The average circumference of the middle upper forearm is approximately 32 + 5 cm for men and 28 ± 6 cm for women. The formula for calculating the area of the muscle region of the middle upper forearm in square centimeters is presented above.

This formula adjusts the upper forearm muscle area for fat and bone. Average values for the mid-upper forearm muscle area are -54 ±11 cm for men and 30 ±7 cm for women. A value less than 75% of this standard (depending on age) indicates depletion of lean body mass. This measurement is affected by physical activity, genetic factors, and age-related muscle loss.

The physical examination should focus on specific symptoms of nutritional deficiencies. Symptoms of PEM (eg, edema, cachexia, rash) should be sought. The examination should also focus on signs of conditions that may predispose to nutritional deficiencies, such as dental problems. Mental status should be assessed because depression and cognitive decline can lead to weight loss.

The widely used Complete Nutritional Assessment (CNA) uses information from the patient's history (eg, weight loss, changes in food intake, gastrointestinal symptoms), physical examination data (eg, loss of muscle and subcutaneous fat, edema, ascites), and the physician's assessment of the patient's nutritional status. The validated Mini Nutritional Assessment (MNA) is used and is also widely used to assess nutritional status in older adults.

Diagnosis of malnutrition

The extent of laboratory testing required is unclear and may depend on the patient's financial situation. If the cause is obvious and can be corrected (e.g., a life-threatening situation), testing is of little use. Other patients require a more detailed assessment.

Signs and symptoms of malnutrition

Region/System	Symptom or sign	Deficit
General appearance	Cachexia	Energy
Skin	Rash	Many vitamins, zinc, essential fatty acids
	Rash on sun-exposed areas	Niacin (pellagra)
	Ease of bruising	Vitamins C or K
Hair and nails	Hair thinning or loss	Protein
	Premature graying of hair	Selenium
	"Spoon-shaped" nails	Iron
Eyes	"Night blindness"	Vitamin A
	Keratomalacia	Vitamin A
Mouth	Cheilitis and glossitis	Riboflavin, niacin, pyridoxine, iron
	Bleeding gums	Vitamin C, riboflavin
Limbs	Edema	Protein
Nervous system	Paresthesia and numbness of the feet and hands	Thiamine
	Cramps	Ca, Mg
	Cognitive and sensory disorders	Thiamine (beriberi), niacin (pellagra), pyridoxine, vitamin B
	Dementia	Thiamine, niacin, vitamin B
Musculoskeletal System	Loss of muscle mass	Protein
	Bone deformities (bow legs, deformed knee joints, curvature of the spine)	Vitamin D, Ca
	Bone fragility	Vitamin D
	Pain and swelling of joints	Vitamin C
Gastrointestinal tract	Diarrhea	Protein, Niacin, Folic Acid, Vitamin B
	Diarrhea and taste perversion	Zinc
	Dysphagia and pain when swallowing (Plummer-Vinson syndrome)	Iron
Endocrine	Enlarged thyroid gland	Iodine

Muscle area of the middle upper forearm in adults

Standard (%)	Men (%)	Women (%)	Muscle mass
100 ±20	54±11	30±7	Adequate
75	40	22	Acceptable
60	32	18	Exhaustion
50	27	15	Cachexia

Mean muscle mass of the mid-upper forearm ± 1 standard deviation. Based on data from the National Health and Nutrition Examination Surveys I and II.

The most commonly used laboratory test is serum protein measurement. Decreases in albumin and other proteins [eg, prealbumin (transthyretin), transferrin, retinol-binding protein] may indicate protein deficiency or PEM. As malnutrition progresses, albumin levels decline slowly; prealbumin, transferrin, and retinol-binding protein levels decline rapidly. Albumin measurement is relatively inexpensive and predicts morbidity, mortality, and case-fatality better than other proteins. However, the correlation of albumin levels with morbidity and mortality may be due to nondietary as well as dietary factors. Inflammation produces cytokines that cause albumin and other dietary protein markers to leave the circulation and enter the tissues, decreasing their serum levels. Because prealbumin, transferrin, and retinol-binding protein decrease more rapidly during starvation than albumin, their measurement is sometimes used to diagnose or assess the severity of acute starvation. However, it is not clear whether they are more sensitive or specific than albumin.

The total lymphocyte count can be calculated and often decreases as malnutrition progresses. Malnutrition leads to a significant decrease in CD4 ⁺ T cells, so this measurement is useful in patients who do not have AIDS.

Skin tests using antigens help to identify weakened cellular immunity in PEM and some other disorders associated with malnutrition.

Other laboratory tests (measurements of vitamin and mineral levels) are used selectively to diagnose specific types of deficiency conditions.

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