People who fast during religious festivals excrete more of a toxic form of arsenic in their urine from the body than those who eat at regular intervals.
Millions of people in some of the poorest regions of the world (e.g. Bangladesh, West Bengalen) are exposed to high levels of arsenic through contaminated drinking water (see EVISA news). Long-term exposure to arsenic in drinking water is known to cause cancer of the skin, lungs, bladder and kidneys as well as causing changes to the skin such as pigmentation and thickening. There are indications that the development of cancer caused by arsenic exposure in such populations is besides other factors dependent on dietary and nutritional factors which can modulate arsenic metabolism.
Many of the people affected practice fasting for at least one month every year during Ramadan when they refrain from consumption of food and fluid during daylight hours. How such practices may modulate arsenic metabolism has not been previously investigated. The new studyParvez Haris at De Montfort University in Leicester
and colleagues investigated this issue by determining total arsenic and arsenic speciation in urine samples from a group of 29 volunteers in the UK. The subjects, not exposed to contaminated water, provided urine samples at the beginning of the fasting and at the end of approximately 12 h of fasting period.
Inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled with ICP-MS was used to measure the total arsenic and arsenic speciation in the urine samples, respectively. The mean total levels of arsenic at the beginning of fasting (18.3 µg g–1 creatinine) and at the end of approximately 12 h of fasting (17.7 µg g–1 creatinine) did not differ significantly (p > 0.05). However, the percentages of urinary arsenic as the methylated arsenic species methylarsonate (MA) were found to be significantly different (p < 0.05) and this species was observed more frequently at the end of fasting, although its overall concentration was similar. There were no significant differences (p > 0.05) in both the concentrations and percentages of other urinary arsenic species detected, namely arsenobetaine (AB) and dimethylarsinate (DMA). Arsenite (As(III)) and arsenate (As(V)) were also analyzed, but were not detected.
The researchers concluded that fasting for a period of 12 h results in a significant increase in the percentage of urinary arsenic as MA, and its frequency of detection in the volunteers at the end of the fasting period is almost nine fold higher. This suggests that metabolism of arsenic is altered by fasting. The original study
Eid I. Brima, Richard O. Jenkins
, Paul R. Lythgoe
, Andrew G. Gault, Dave A. Polya
, Parvez I. Haris, Effect of fasting on the pattern of urinary arsenic excretion
, J. Environ. Monit., 9/1 (2007) 98. DOI: 10.1039/b613340a Related studies:
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, Environ. Res. (U.S.A), 100/1 (2006) 115-122. doi:10.1016/j.envres.2005.03.009 Related News:
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EVISA News, June 22, 2005: Arsenic desaster in Bangladesh man-made ?
EVISA News, June 27, 2005: Susceptibility to arsenic toxicity influenced by genes
EVISA News, July 29, 2005: Arsenic-free water still a pipedream
EVISA News, January 18, 2005: Hungarians exposed to high arsenic levels in drinking water
EVISA News, September 7, 2006: New Agilent HPLC column for routine determination of arsenic species in human urine by HPLC-ICP-MS
last time modified: January 17, 2007