ZURICH, SWITZERLAND. Diuretics such as furosemide (Lasix) are universally used in the treatment of hypertension and congestive heart failure. Medical researchers at the Zurich University Hospital now warn that the use of diuretics may lead to a thiamin (vitamin-B1) deficiency that in turn may further impair heart function. The researchers cite several recent studies that have clearly established an association between diuretics and urinary thiamin loss. They also point to other studies that have found that 50 per cent of elderly people and 80 per cent of heavy alcohol users suffer from a thiamin deficiency even without taking diuretics. A very recent study concluded that injection of 200 mg/day of thiamin followed by six weeks of oral supplementation with 200 mg/day improved the heart function very significantly in heart failure patients taking diuretics (left ventricular ejection fraction increased by 22 per cent).
The use of diuretics has also been linked to an increase in homocysteine levels and a decrease in magnesium levels. Magnesium is very important for heart health and is also necessary in order to convert thiamin to its active form (thiamin pyrophosphate). The Swiss researchers make the interesting observation that poor appetite is a powerful indicator of a thiamin deficiency in elderly patients with congestive heart failure. They suggest that supplementation with 20-50 mg/day of thiamin should be tried in elderly heart failure patients. This intervention is inexpensive, safe and usually shows results within a few days. They also suggest that supplementation with folic acid and magnesium may be beneficial in order to counteract the homocysteine increase and magnesium depletion often accompanying diuretic use. [52 references]
Suter, Paolo M. and Vetter, Wilhelm. Diuretics and vitamin B1: are diuretics a risk factor for thiamin malnutrition? Nutrition Reviews, Vol. 58, October 2000, pp. 319-23