MRFIT Study – What did it tell us?

The Australian Broadcaster ABC televised the program Heart of the Matter Part 1 – Dietary Villains on Thursday, 24 October 2013. This program listed the MRFIT study as more evidence that cholesterol is not implicated in heart disease.

The Multiple Risk Factor Intervention Trial (MRFIT) was a coronary heart disease prevention trial that was conducted at 22 US clinical centres (18 cities) from 1973 to 1982. The multiple risks evaluated were:

A number of popular commentators use this trial as proof that cholesterol is not implicated in heart disease.

The tobacco industry also used the results of the MRFIT study to argue that smoking is not harmful.

MRFIT Results

12,866 men between the ages of 35-57 with one or more of these risk factors were randomly assigned to the Special Intervention (SI) or Usual Care (UC) group and followed for 6-8 years.

UC men were given information on risk factors, referred to their usual sources of care, and re-examined annually.

SI participants received group and individual counselling on a fat-modified diet, a stepped-care drug treatment program for diastolic hypertension (after an initial attempt at blood pressure control by weight reduction, if indicated), and, for cigarette smokers, counselling aimed at cessation. ¹

In Special Intervention group, serum cholesterol was only 3– 2% lower than in Usual Care group. There was a 30% reduction of smokers in the Special Intervention group. CHD deaths were 7% lower in Special Intervention group.

So the results are not spectacular.

Note that the Usual Care group was not a No Treatment group. They were making changes that resulted in lowering their risk factors. CHD mortality was declining in the USA, Canada and Australia but not in the United Kingdom.

Initially, the drug hydrochlorothiazide was used in the trial to lower blood pressure. However, this drug:

The use of this drug did distort results.

The results after 16 years are more impressive. After 16 years, those who had been in the intervention group, CHD deaths were 11.4% lower and total mortality was 5.7% lower than the Usual Care group

Serum Cholesterol and Risk of Premature Death

There were 356 222 men aged 35 to 57 years, who were free of a history of hospitalization for myocardial infarction, that were initially screened by the MRFIT program in its recruitment program.

This provided researchers with a group that had standardised serum cholesterol measurements and long-term (6 years) mortality follow-up. ⁵

For the entire group aged 35 to 57 years at entry, the age-adjusted risks of CHD death in cholesterol quintiles are shown below.

Quintile	Cholesterol (mg/dL)	Cholesterol (mmol/L)	Age-Adjusted Risk
1	< 182	< 4.71	1
2	182-202	4.71-5.22	1.29
3	203-220	5.23-5.70	1.73
4	221-244	5.71-6.31	2.21
5	> 244	> 6.31	3.42

The conclusion from this paper is that:

For these men that were initially screen for the MRFIT cohort and without a history of myocardial infarction, low risk was defined as:

Only 2% of the men in the MRFIT cohort met these criteria. Only 6 of these men died from CHD during the 6-year follow-up, and the CHD death rate was 87% lower than for the rest of the cohort. ⁶

Significance of Dietary Fats

Results from the MRFIT were used to determine the effects of polyunsaturated fat acids on coronary heart disease. ⁷

WHO Trial in Belgium, Italy, Poland and UK

Another study was the WHO Collaborative Trial of Multifactorial Prevention of CHD which involved over 60,000 middle aged men in a total of 80 factories in Belgium, Italy, Poland and the UK ⁸. The interventions were:

Belgium had the greatest reduction in the risk factors with corresponding reductions in outcomes in the intervention group for:

Last updated on Wednesday 29 January 2025 at 07:02 by administrators

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1. Kjelsberg, M. O. et al. (1997) Brief description of the Multiple Risk Factor Intervention Trial. American Journal of Clinical Nutrition. 65191S–5S.
2. van Brummelen, P. et al. (1979) Influence of hydrochlorothiazide on the plasma levels of triglycerides, total cholesterol and HDL-cholesterol in patients with essential hypertension. Current Medical Research and Opinion. 6 (1), 24–29.
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