University of Minnesota

Finnish Mental Hospital Trial

Study Category: The Prevention Trials (1946-1973)
Years: 1959 - 1971
Location: Finland
Principal Investigator: Turpeinen, O.
External Resource: View URL


Finnish pioneers in the epidemiology of nutrition and coronary heart disease (CHD) were the earliest to carry out a rigorous trial of diet and CHD.


The investigators used an innovative design, beginning in 1958, in which two Helsinki mental hospitals were assigned experimental diets for 6 years at which point the diets crossed over for another 6 years. (1)

The annual loss of subjects was 13-16 percent, and they were replaced by other patients annually. Age and sex composition remained stable. The Finnish high-fat diet was compared to one with soy milk, unsaturated margarine, vegetable oils, and reduced meat and dairy fat, resulting in a marked decrease in saturated and increased unsaturated fatty acids and an eventual 51 mg/dl difference in serum cholesterol levels due to diet. This is among the largest decrease reported for diet trials.


The approach demonstrated the feasibility of such institutional changes reducing serum and tissue concentrations of lipid, and at 6 years, the study found diminished clinical and electrocardiographic events and mortality in the experimental hospitals. (1) Conclusion of the trial after the 12 years and cross-over diets revealed the hypothesized lowering in risk factor levels and CHD events during the experimental diet periods. Coronary deaths were about half that in the control period.(2)


The trial was important because it was made in a region of high saturated fatty acid intake and high CHD event rates, because it was among the earliest trials and had an unique design of experimental and control diets crossed over after 6 years, and because it achieved significant changes in risk and disease rates, along with excellent adherence to the diet and institutional control. End differences could not be explained by entry differences in the groups. The authors conclude: “. . the use of a serum-cholesterol lowering diet, ie. a diet low in saturated fats and cholesterol and relatively high in polyunsaturated fates, exerted a substantial preventive effect upon coronary heart disease.” Limitations of the trial were the absence of individual subject randomization and the heavy rate of entry and exit of participants to and from the experimental groups. (HB)


1. Turpeinen, O., Karvonen, M.J., Pekkarinen, M., Miettinen, M., Reino, E., and Paavilainen, R. 1968. ‘Dietary prevention of coronary heart disease: long-term experiment’. American Journal of Clinical Nutrition, vol. 21, pp. 255-276.

2. Turpeinen, O., Karvonen, M.J., Pekkarinen, M., Miettinen, M., Elosuo, R., and Paavilainen, E. 1979. ‘Dietary prevention of coronary heart disease: The Finnish Mental Hospital Study’. International Journal of Epidemiology, pp. 99-118.