Diuretics thiamin excretion

Diuretics, long-term Accelerate thiamin excretion and... 

Thiamin that is not bound to plasma proteins is rapidly filtered at the glomerulus. Diuresis increases the excretion of the vitamin, and patients who are treated with diuretics are potentially at risk of thiamin deficiency. Some of the diuretics used in the treatment of hypertension may also inhibit cardiac (and other tissue) uptake of thiamin, thus further impairing thiamin status, which may be a factor in the etiology of heart failure (Suter and Vetter, 2000). 

Chronic alcoholism may also precipitate beriberi since alcohol cannot be converted to fat in the body, but must be metabolized by the same thiamin- dependent processes as carbohydrate and protein. Furthermore, alcohol increases urinary excretion of water (diuretic effect) and water-soluble vitamins. A similar, but lesser, effect may result from the heavy consumption of caffeine (in beverages such as coffee, colas, and tea) coupled with a diet chronically high in refined foods which are rich in carbohydrates. (Like alcohol, caffeine is a diuretic. Also, it stimulates the utilization of stored carbohydrate for energy.)... 

Alcohol is an important factor in causing thiamin deficiency because it inhibits the active transport of thiamin across the gut and when abused it impairs the quality of the diet consumed. Diuretics accelerate the excretion of thiamin and appear to override the renal conservation mechanism. Their use is of potential concern in elderly people whose diet may be poor for other medical reasons and their physicians may be unaware of their need for supplemental nutrient. 

---