"We found that one-third of congestive heart failure patients admitted to our hospital had red blood cell levels of thiamin that were lower than normal and would suggest deficiency. In contrast to some previous studies, we did not find a relationship between the development of thiamin deficiency and the amount or duration of diuretic use and urinary thiamin excretion. In fact, what was important was that a relatively small dose of thiamin from a multi-vitamin was protective against developing thiamin deficiency," said Mary E. Keith, Ph.D. from St. Michael's Hospital in Toronto, Ontario, Canada.
Dr. Keith said that heart failure may increase the body's need for certain nutrients, including thiamin, so even patients who are eating relatively well may not be getting enough of them. At the same time, the illness may make it harder to maintain a proper diet. She said that this study helps focus attention on the role of diet in managing serious conditions, such as heart failure.
"Physicians and the public have exclusively focused on drug therapy to the detriment of at least one of the foundations of good health-appropriate nutrition," she said.
Thiamin, also called vitamin B1, helps the body to digest carbohydrates and perform other functions. Like other B vitamins, thiamin is not stored in the body, so poor diet can lead to deficiency in a relatively short period of time and possibly worsen the symptoms of heart failure. Although thiamin deficiency has not been extensively studied among heart failure patients, the researchers said that there are several reasons to be concerned about the problem. For instance, many heart failure patients have poor diets, and some earlier studies have indicated that diuretic medicines prescribed to help treat the condition may increase the losses of thiamin.
This study is the largest study yet of thiamin deficiency among hospitalized heart failure patients, and it included participants with various degrees of illness. The researchers, including lead author Stacy A. Hanninen, R.D., M.S.C., measured the thiamin levels of 100 consecutively admitted patients with heart failure. They also measured the thiamin levels of 50 healthy people. The heart failure patients were almost three times as likely to be deficient in thiamin as the control subjects (33 percent versus 12 percent, p = 0.007).
"Our sample is quite representative of our hospitalized population of heart failure patients. We also used a direct measurement of thiamin status--the erythrocyte thiamin pyrophosphate--which is more specific than earlier assays that indirectly measured enzyme activity. Finally, our study also investigated factors other than diuretic medication, such as diet, medical status and demographic factors that might be contributing to the development of thiamin deficiency," Dr. Keith said.
In contrast to earlier studies, these results did not show an association between the use of diuretic medications and thiamin deficiency. However, Dr. Keith said that their report is not the final word on this point.
"The relationships between thiamin loss, thiamin status and diuretic use are not definitively established and controversy remains. Our population was a cross-section of hospitalized patients who had differing levels of disease severity and had differing doses of diuretics prior to their admission, which may have accounted for the lack of relationship between diuretic dose and thiamin deficiency," she said.
Dr. Keith also pointed out that although they observed that patients taking supplements were less likely to be deficient in thiamin, the association did not reach statistical significance (p = 0.06). Further studies are needed to determine whether improving thiamin levels, either with supplements or via other means, will improve heart failure symptoms.
Professor John G.F. Cleland, F.A.C.C., from the University of Hull in Hull, U.K, who was not connected with this study, said that there are many reasons for heart failure patients to have difficulties maintaining proper nutrition, so it is surprising that so little attention has been paid to nutrition in heart failure.
"Patients with advanced heart failure commonly suffer from cardiac cachexia, but little is known about the mechanisms underlying this problem or how to treat it. Deficiency in one dietary component, such as thiamin, is unlikely to occur in isolation and might be a marker for shortages of other micronutrients. Recent research suggests that targeted multi-micronutrient supplementation may improve quality of life and left ventricular function in elderly patients with heart failure," Dr. Cleland said.
Jill Kalman, M.D. from the NYU Medical Center in New York, N.Y., who also was not connected with this study, said the results help point the way toward improving care for heart failure patients.
"If we can start to point out where there are certain metabolic deficiencies in heart failure, learn where we can replace them in an effective and safe fashion, and make a difference eventually in terms of outcomes, I think that's where this is an important article," Dr. Kalman said.
Dr. Kalman said that it is also important to find out whether any heart failure treatments may be causing metabolic deficiencies.
This study was funded by a research grant from the Canadian Foundation for Dietetic Research, Dietitians of Canada, Toronto, Ontario.
Dr. Cleland is a consultant to Numico, a company interested in nutritional supplements for heart failure patients.