By: Janet Riley
To read last week’s headlines, one might think it prudent to substitute a glass of olive oil for your regular daily orange juice. According to the Los Angeles Times, “Mediterranean diet sinks low-fat menu.” A Mediterranean diet, even drenched in olive oil and studded with nuts, beats a low-fat diet hands-down in preventing strokes and heart attacks in healthy older people at high risk of cardiovascular disease, according to new research.”
Reports said that thousands of people were followed over approximately five years. One group was placed on a Mediterranean diet and provided supplemental olive oil. A second group was placed on a Mediterranean diet supplemented with nuts. And a third was instructed to follow a low fat diet, was not given any total caloric restrictions and received non-food gifts.
As I’ve learned to do, I decided to check out the original study and read the comments. Here’s the scoop: People in the low fat diet control group had a difficult time following advice to reduce fat in the diet, a challenge that is well known. Their diet was 37 percent fat, when nutritionists consider a low fat diet to be much lower – in the ten percent range.
Despite the glowing headlines, the nutrition community was skeptical and even hostile. Here’s a sampling of comments, including one from the noted low-fat diet promoter Dean Ornish, M.D.:
Flawed Study: Control Group Was Not Eating a Low-fat Diet!
Dean Ornish, M.D., Sausalito, CA
This study is highly flawed:
• The control group did not follow a low-fat diet. The authors wrote, “We acknowledge that, even though participants in the control group received advice to reduce fat intake, changes in total fat were small.” This is not surprising since they gave the control group little support in following this diet during the first half of the study.
In the “low-fat” group, total fat consumption decreased insignificantly from 39% to 37% (Table S7, appendix). This is much higher than the American Heart Association guidelines of a low-fat diet (<30% fat) or ours for reversing heart disease (<10% fat).
• There was no significant reduction in heart attacks, death from cardiovascular causes, or death from any cause. They only found a significant reduction in death from stroke (Table 3). They only found a reduction in cardiovascular causes when these were pooled with deaths from stroke (Table 3).
The conclusion should be, “We found a significant reduction in stroke in those consuming a Mediterranean diet when compared to those who were not making any significant changes in their diet.”
Cannot believe you published this article
John Forrest, M.D., Physician, San Diego, CA
Dr. Lenz’s comments are right on. The control “low fat group” was not on anything resembling a low fat diet. Please compare published results of Pritikin, Ornish, and Esselstyn for results while on a low fat diet. Allowing their conclusion that Mediterranean diet was shown to be better for CV protection than a low fat is shameful for the premier medical journal. As you can see I am enraged at your handling of this material and would appreciate an editorial response.
Why the astonishing low cardiac event incidence in the control group?
Matthew Higgins, Hoboken, NJ
The study finds 109 cardiac events among 2,450 control panel participants, out of 9,763 total years of participation. This translates into event incidence (heart attack, stroke, or death) of about 1.1 percent a year. (Event in the Mediterranean diet group was even lower, of course, at about 0.8 percent a year.) For a middle aged male, “high risk” group, cardiac event incidence should be at least twice as high. Indeed, 1.1 percent annual risk is what one should find for an exceptionally healthy group. The authors seem to acknowledge this point: “As with many clinical trials, the observed rates of cardiovascular events were lower than anticipated, with reduced statistical power to separately assess components of the primary end point.” But the results seem to speak not to statistical power to discriminate between control and intervention incidence, but rather to the overall representativeness and design of the panel. I wonder if the authors have a response. Otherwise, the headline could be: “Study participation cuts heart disease risk in half–with no lifestyle changes.”
One reporter who caught on was Sanjay Gupta, M.D. on CNN who said, “I think the headline may be ‘low fat diet very hard to stay on’,” Gupta said. “But if the question they were trying to answer was which is better, they didn’t answer that.”
While the study’s focus wasn’t meat, the disparity in headlines versus comments from nutrition researchers suggests reporters need to “crack” these studies a little harder to deliver more accurate reports.