The human body is uniquely equipped to handle starvation. Within 8 hours of no food intake the body begins to alter metabolism. After a period of 8-12 hours the body has likely used up all its reserves of glucose and must begin to break down the glycogen stored in the liver and muscles for energy. After glycogen stores are depleted the body resorts to using amino acids for energy. The body can survive for about three days this way before shifting metabolism again to preserve lean body tissue. To prevent excess muscle loss, the body begins to rely on fat stores to create ketones for energy. This process is known as ketosis. Significant weight loss will occur in this period. The larger one’s composition of fat the longer they can survive this way. Once all the fat is depleted the body will once again have to use muscles for energy through a process known as gluconeogenesis. This will continue until vital organs, which are composed of muscle, become atrophied which leads to total organ failure and subsequently death. Human bodies are incredibly resilient maintaining itself for weeks to months without food. As seen in patients with Anorexia Nervosa and prisoners of war, if someone has been starved for a prolonged period of time, they cannot resume eating normally right away as this could cause a fatal syndrome known as Refeeding Syndrome. (Silver, 2018)
Refeeding syndrome describes the metabolic and clinical signs associated with rehabilitation of malnourished subjects. During a period of refeeding a patient may experience low levels of phosphate, potassium, and magnesium all of which can lead to heart function abnormalities; sodium retention, and hyperglycemia. Under severe conditions these changes themselves can lead to multiple organ failure and death. The pathophysiology behind refeeding syndrome is related to the switch the body made from utilizing carbohydrates as a primary energy source to using proteins and fats as a primary energy source. Upon refeeding the body instantly shifts back to carbohydrate metabolism which leads to an increase in insulin and re-uptake of glucose and micronutrients from the blood stream. Low levels of these micronutrients in the blood have serious effects such as hypotension, bradychardia, weakness, heart failure, and arrhythmia. To avoid this, patients should be re-nourished slowly following a protocol of 10 kcal/kg per day and slowly increasing calories consumed each day. Patients should also be on a vitamin B complex, thiamin, and multivitamin supplements during refeeding. (Obeid, Hachem, and Ayoub, 2014)
As I researched starvation and refeeding I learned, the physiology of starvation itself has not been examined in depth since the 1940’s during the Minnesota Starvation and Refeeding experiment in which scientists purposefully starved and re-fed 32 male subjects (Brooke, et al, 1950). Scientific review boards have deemed that experimenting in this way, purposefully starving a subject to gain knowledge, is unethical. Due to this scientists are limited to observing ‘natural” cases of starvation as one may observe in a patient with Anorexia Nervosa or a patient undergoing chemotherapy. This has led to a lack of in depth knowledge on how the body shifts metabolism and the steps it takes to create fuel during starvation. Most of our knowledge currently comes from the study of animal starvation or from the experiments that took place in the 1940’s. Most general practitioners have not heard of refeeding syndrome and would not be able to diagnose it in a patient they were treating, The Physiology of starvation and refeeding needs to be included in every medical curriculum so patients experiencing malnutrition do not slip through the cracks and suffer a fatal heart attack that was entirely preventable.
Sources:
Keys, A., Brozek, J., Henschel, A., Michelsen, O., Taylor, H. L., Simonson, E., ... & WELLS, S. (1950). The biology of human starvation. Volumes 1 and 2. The biology of human starvation. Volumes 1 and 2.
Mehanna, H., Nankivell, P. C., Moledina, J., & Travis, J. (2009). Refeeding syndrome–awareness, prevention and management. Head & neck oncology, 1(1), 4.
Obeid, O. A., Hachem, D. H., & Ayoub, J. J. (2014). Refeeding and metabolic syndromes: two sides of the same coin. Nutrition & diabetes, 4(6), e120.
Silver, Natalie (2018). How Long can you live without food? Healthline. Retrieved from: <https://www.healthline.com/health/food-nutrition/how-long-can-you-live-without-food>
No comments:
Post a Comment