This week’s news came to us by way of a randomized controlled trial, which I’ve argued repeatedly is the best kind of study to determine how one thing causes another.
The Minnesota Coronary Experiment was a well-designed study that was conducted in one nursing home and six state mental hospitals from 1968 to 1973. More than 9,400 men and women, ages 20 to 97, participated. Data on serum cholesterol were available on more than 2,300 participants who were on the study diets for more than a year.
At baseline, participants were getting about 18.5 percent of their calories from saturated fat, and about 3.8 percent from unsaturated fats. The intervention diet was considered a more “heart healthy” one. It encouraged a reduction in the amount of calories from saturated fats (like animal fats and butter) and more from unsaturated fats, particularly linoleic acids (like corn oil). The intervention diet lowered the percent of calories from saturated fats to 9.2 percent, and raised the percent from unsaturated fats to 13.2 percent.
The average follow-up for these participants was just under three years. In that time, the total serum cholesterol dropped significantly more in those on the intervention diet (-31.2 mg/dL) than in those on the control diet (-5 mg/dL).
There was, however, no decreased risk of death. If anything, there seemed to be an increased mortality rate in those on the “heart healthy” diet, particularly among those 65 years and older. More concerning, those who had the greater reduction in serum cholesterol had a higher rate of death. A 30mg/dL decrease in serum cholesterol was associated with a 22 percent increase in the risk of death from any cause, even after adjusting for baseline cholesterol, age, sex, adherence to the diet, body mass and blood pressure.
Of course, this is only one study. It involved only institutionalized patients. Only about a quarter of the participants followed the diet for more…