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Nutrition is the process by which nutrients are taken in and used by the body to support overall health and essential functions, such as metabolism, growth, and maintaining and repairing body tissues. When nutrition is imbalanced, it's called malnutrition. Now, malnutrition can be overnutrition, or the ingestion of more nutrients and energy than the body needs; or undernutrition, where nutrient and energy intake is insufficient to meet the body’s daily needs.
Okay, let’s review the different types and causes of malnutrition. First, starvation-related malnutrition, also called primary protein-calorie malnutrition, occurs when nutritional needs aren’t met due to starvation, like with anorexia nervosa. Then, there’s chronic disease–related malnutrition, also known as secondary protein-calorie malnutrition, where dietary intake is insufficient to meet the increased metabolic demands related to chronic inflammatory conditions, like rheumatoid arthritis. Lastly, there’s acute disease–related or injury-related malnutrition, where there is significant inflammation, like with major infections, burns, and trauma, and dietary intake is unable to supply enough calories for energy or protein for tissue repair.
So, there are several risk factors for malnutrition, including socioeconomic factors, like food insecurity; health conditions, like prolonged physical illness, surgery, trauma, or prolonged immobility; incomplete diets, like with fad diets or poorly planned veganism; and malabsorption, like with vitamin B12 deficiency that occurs when intrinsic factor is lost after a gastrectomy.
Now, as protein stores are depleted, synthesis of plasma proteins, like albumin, decreases. This lowers oncotic pressure in the intravascular space, which causes a shift of fluids out into the interstitial tissues, leading to edema, as well as drying of the skin and mucous membranes. Protein deficits can also result in brittle nails and hair loss, as well as decreased muscle mass. Finally, other clinical manifestations include weight loss, decreased muscle strength, easy fatigability, and decreased ability to perform activities of daily living.
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