A Study of Diurnal Variation in Serum and Urine Osmolalities and in Serum Cortisol During Ramadan Fasting: Evidence Suggesting Increased Intrinsic Water Production
Daily abstinence from food and drink for some 15 hours in Ramadan is a unique type of fasting. Morning (0800 hour) and evening (1900 hour, just preceding sunset) estimation of serum and urine osmolalities and of serum cortisol were conducted on 22 healthy volunteers who fasted Ramadan of 1407 Hijri in Mosul on days 1, 14 and 28 of the month. A diurnal variation in serum and urine osmolalities that narrowed as Ramadan progressed was observed. The evening serum cortisol was high on days 1 and14 but decreased on day 28. In four of the 66 occasions comparing morning and evening serum osmolalities the evening values were 2 mOsmol/kg lower than morning values.
Our results were interpreted as unexplainable by vasopressin action on the kidney alone. Evidence that daily fasting triggers increased capacity to synthesize and store glycogen which is dictated by increased glucose needs
for the new prolonged intermeal interval is given. We maintain that glycogen synthesis during eating hours incorporates water intracellularly; water is released during daytime glycogenolysis in order to help prevent undue increase in serum osmolality during fasting. Our concept offers explanations for many phenomena that are experienced by people who fast Ramadan.
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