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Is water fasting safe?

A recent study investigated the safety of medically supervised, water fasting at an integrative medical center in Santa Rosa, California.

Fasting may take many forms, but it generally involves abstaining from certain foods and beverages for some period of time. Fasting is increasingly touted for its health-promoting benefits, including the breakdown of fats and lipids, reduced oxidative stress and inflammation, and an increased ability to modulate hormones and to resist the physiologic effects of stress. These benefits may explain the results of studies indicating that fasting benefits individuals with chronic conditions such as hypertension, metabolic syndrome, chronic pain, and fibromyalgia.

Previous studies on water fasting had serious complications

Water-only fasting involves a complete abstinence from food and beverages with the exception of pure water. This method was studied in the 1960s and 1970s as an obesity treatment, but serious complications—including death—were reported in a few cases and studies slowed or ceased. It was unclear whether water-only fasting caused these complications or whether they resulted from other causes such as unsafe fasting regimens. The practice continued and although protocols were developed to address safety concerns and contraindications for fasting, these measures have not been widely studied.

Using data collected over a five-year period from the charts of 768 patients at the True North Health Center in Santa Rosa, California in the United States, researchers assessed the frequency, severity, and nature of adverse events associated with water-only fasting. The center uses a detailed, medically supervised fasting protocol that meets standards set by the International Association of Hygienic Physicians. The protocol includes guidelines on contraindications, preparations for fasting, medical supervision, and refeeding after fasting.

The patients’ data were included if they fasted for at least two consecutive days with a refeeding period half of the fast length. As some patients fasted multiple times, data were aggregated across patient visits. Chart data on adverse events were derived from self-reports and clinical and diagnostic findings. Adverse events were graded based on severity as either mild, moderate, severe, life-threatening or disabling, or resulting in death. Fasts were categorized based on length, which ranged from two to seven days to twenty-two days or more. The results were recently published in the journal BMC Complementary and Alternative Medicine.

Water fasting led to mostly mild or moderate adverse events

Adverse events included complaints like headache, nausea, fatigue, musculoskeletal pain, dyspepsia, presyncope, and hypertension. During the entire protocol period, the highest-grade adverse events experienced in just over 70% of patient visits were either mild or moderate events that occurred over 555 visits. The highest-grade adverse events in about one-quarter of visits (212) were deemed severe but not life-threatening. There was only one life-threatening event and no deaths that occurred. Two events were considered serious adverse events based on the criteria set forth by the Department of Health and Human Services. These events occurred in older adults and required temporary hospitalizations. Older adults and those who fasted longer had more events of a higher grade, although these relationships were not considered strong associations.

This is the most comprehensive analysis of the adverse events associated with medically supervised water-only fasting to date. Overall, the results of this study suggest that medically supervised, water-only fasting is generally safe and well tolerated; however, the study is not without limitations. As it was limited to one health center, results may not generalize to other sites or patient populations. Randomized controlled trials with comparison groups and investigator blinding are needed to further corroborate these results. Further research is needed to investigate factors that contribute to adverse events such as the duration of treatment, age, and pre-existing conditions.

Written by Suzanne M. Robertson, Ph.D.

Reference: Finnell, John S., Bradley C. Saul, Alan C. Goldhamer, and Toshia R. Myers. “Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting.” BMC complementary and alternative medicine 18, no. 1 (2018): 67.



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