Research appearing in the Journal of the American College of Cardiology (2006; 47: 354-61) looked at the incidence of thiamin deficiency in patients with congestive heart failure, when compared to a healthy control group. The researchers found that 33% of a cross section of 100 hospitalized congestive heart failure (CHF) patients were found to be deficient in thiamin, as compared with only 12% in a control population (50 subjects).

Patients on the diuretic furosemide (sold under the brand name Lasix) tend to be deficient in thiamin. A study appearing in The American Journal of Medicine (1991;151-155) measured thiamin status in 23 patients with congestive heart failure, and who were taking furosemide.  A high thiamin pyrophosphate effect, which indicates thiamin deficiency, was found in 21 of the 23 subjects. Thiamin deficiency was only found in two out of 16 controls. This result was confirmed by other research appearing in the Journal of the American College of Cardiology (2006; 47: 354-61), which found that 33% of 100 hospitalized patients with congestive heart failure were thiamin deficient. Only 12% of healthy controls were found to be thiamin deficient.

Beriberi is the disease of thiamin deficiency. Wet beriberi affects the cardiovascular system and is characterized by an enlarged heart, and congestive heart failure. There is some research that indicates supplementation with thiamin may be of benefit to patients with congestive heart failure. A study appearing in The American Journal of Medicine (May 1995;98:485-490)looked at 30 patients with severe congestive heart failure who were also taking furosemide. In the double-blind study, the patients were given either IV thiamin (200 milligrams per day) or a placebo. The thiamin group experienced improvement in left ventricular ejection fraction–increasing by 22% in 27 patients who completed the full seven-week therapy. The authors of the study concluded that thiamin supplementation would be a beneficial addition to conventional therapy for congestive heart failure.