Beer has a very low content of sodium and protein–and if an individual subsists solely on beer they have a very limited solute intake. This is important because the limit on how much free water excretion can be achieved in a day is dependent on urine osmolality (urine flow rate = rate of solute excretion / urine osmolality). For an individual drinking predominantly beer, they are taking in only about 300mosm of solute per day, which is then eliminated in the urine. This puts a cap of only about 4-5 Liters of electrolyte-free water that can be excreted in a day. Thus, if an individual drinks more than 4-5 Liters of beer in a day, in the absence of additional solute, they will become hyponatremic. On top of this mechanism, beer drinkers may also have non-osmotic secretion of ADH as a result of volume depletion from chronic GI losses or vomiting. This can result in profoundly low serum sodium levels and all the neurologic complications which go along with it. The same general mechanisms (low solute intake, high fluid intake) are also at play in elderly women eating a “tea and toast” diet.