Now We’re All Going Mediterranean?

I’m getting a lot of emails about this study:

BACKGROUND: Observational cohort studies and a secondary prevention trial have shown an inverse association between adherence to the Mediterranean diet and cardiovascular risk. We conducted a randomized trial of this diet pattern for the primary prevention of cardiovascular events.

METHODS: In a multicenter trial in Spain, we randomly assigned participants who were at high cardiovascular risk, but with no cardiovascular disease at enrollment, to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). Participants received quarterly individual and group educational sessions and, depending on group assignment, free provision of extra-virgin olive oil, mixed nuts, or small nonfood gifts. The primary end point was the rate of major cardiovascular events (myocardial infarction, stroke, or death from cardiovascular causes). On the basis of the results of an interim analysis, the trial was stopped after a median follow-up of 4.8 years.

RESULTS: A total of 7447 persons were enrolled (age range, 55 to 80 years); 57% were women. The two Mediterranean-diet groups had good adherence to the intervention, according to self-reported intake and biomarker analyses. A primary end-point event occurred in 288 participants. The multivariable-adjusted hazard ratios were 0.70 (95% confidence interval [CI], 0.54 to 0.92) and 0.72 (95% CI, 0.54 to 0.96) for the group assigned to a Mediterranean diet with extra-virgin olive oil (96 events) and the group assigned to a Mediterranean diet with nuts (83 events), respectively, versus the control group (109 events). No diet-related adverse effects were reported.

CONCLUSIONS: Among persons at high cardiovascular risk, a Mediterranean diet supplemented with extra-virgin olive oil or nuts reduced the incidence of major cardiovascular events.

Others have summarized the findings here and here. The findings presented are that eating a Mediterranean diet reduced the risk of cardiovascular events. We should note that there are plenty of conflicts of interest here, although that doesn’t discount the findings.

But there is one thing that eagle-eyed reader Brad F. pointed out to me in email. I take you to Table S5, in the appendix, which I have edited here. What you’re seeing are the percentage of people who endorsed eating these 14 items in the Mediterranean Diet Score 5 years into the study. In many columns, the differences between groups appear to be clinically small. I highlighted the really big differences I see.

MEDiet + EVOO MeDiet + nuts control
1. Use olive oil as main culinary fat 99.9 97.5 96.3
2. Olive oil >4 tablespoons 93.6 79.5 58.9
3. Vegetables ≥ 2 servings/d 74.1 73.7 64.5
4. Fruits ≥ 3 servings/d 65.2 67.9 60.9
5. Red or processed meats < 1/d 97.3 96.6 97.1
6. Butter. cream. margarine < 1/d 97.8 96.6 94.8
7. Soda drinks < 1/d 94.6 93.9 94.7
8. Wine glasses ≥ 7/ wk 29.9 32.3 25.1
9. Legumes ≥3 /wk 41.5 36.9 31.2
10. Fish or seafood ≥ 3/wk 74.7 75.9 66.1
11. Commercial bakery ≤ 2/wk 75.9 73.5 71.9
12. Nuts ≥ 3/wk 42.2 90.7 16.7
13. Poultry more than red meats 84 84 83.2
14. Use of sofrito sauce ≥ 2 /wk 86.9 84.3 65.1

Also sofrito sauce, I guess, but that’s made with olive oil! Although this is being sold as a “Mediterranean Diet” study, what it really looks like is a regular diet supplemented with either tons of olive oil or nuts. Otherwise, there’s not that much difference between what they are eating, no? You also have to remember that they gave the people free nuts or free olive oil as supplements for years.

So rather than say this study proved a Mediterranean diet reduced the risk of heart disease, what it might say is that giving people free olive oil or free nuts every day for years and recommending they take them for years reduces the risk of heart disease. But that’s not what I’m reading; nor evidently is Brad.

[Originally posted at The Incidental Economist]