30 for mortality
The numbers presented are from the best studies that are currently available. Some of these studies will NEVER be repeated and so this is all we'll ever have to go on. There will be continued study in some areas and we aim to incorporate this forward into our site. We're constantly monitoring the literature for updates (if you think there is something we've missed, email us!). The conclusions we draw are a best estimate, folks. We've presented what we think is the closest thing to the truth about this intervention, but our data is only as good as the studies that underlie it — and often, the studies aren't as complete or as good as we'd like. We present one number here for the NNT, but please realize this is an estimate and there is a range for what this intervention can offer a given person. That range will depend upon the person's spectrum of disease (mild/moderate/severe), their demographic, their subtype of disease, the setting of the intervention, their general health, and literally thousands of other variables. Using these numbers in practice means taking a number of large leaps about all of these variables, and also about the veracity of the underlying research. Therefore, as with any 'high quality' data, the application of data requires a doctor's expertise and deliberate consideration.
In Summary, for those who adhered to the Mediterranean diet:
- 94% saw no benefit
- 6% were helped by preventing a repeat heart attack
- 3% were helped by preventing death
- 3% were helped by preventing cancer
- 0% were harmed
In Other Words:
- 1 in 18 were helped (preventing repeat heart attack)
- 1 in 30 were helped (preventing death)
- 1 in 30 were helped (preventing cancer)
- None were harmed
Where We Get The Numbers:
Source: de Lorgeril M, Salen P, Martin, J, et.al. Mediterranean Dietary Pattern in a Randomized Trial. Archives of Internal Medicine 1998, 158: 1181-7.
de Lorgeril M, Renaud S, Mamelle N, et al. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. The Lancet; Jun 11, 1994; 343:1454-9.
Efficacy Endpoints: Overall survival, new cancers, heart attack
Harm Endpoints: None
Narrative: Background: The Mediterranean population is known to have a lower incidence of coronary heart disease compared to other groups.1 It is unclear what the reason for this is, speculation is mostly dietary and includes the protective effects of olive oil (linoleic acid) or flavonoids in red wine, the heavy reliance on fruits and vegetables, and the relative paucity of dairy and red meat. The “typical” Mediterranean diet:
- abundant fruits and vegetables
- olive oil as the principal source of fat
- fish and poultry consumed in low to moderate amounts
- dairy consumption is mostly of cheese and yogurt (less butter/cream)
- red meat consumed in low amounts
- red wine in low to moderate amounts
Mediterranean diets are low in saturated and omega-6 fats, but high in omega-3 fats, oleic acids, fiber, antioxidants, vegetable proteins, and B vitamins.
Study Descriptions: In this single blinded secondary prevention trial 605 survivors (10% female) of a first acute myocardial infarction were randomized to the American Heart Association Step 1 diet or to a Mediterranean-type diet for 5 years. Patients randomized to the Mediterranean-type diet were given free quantities of a rapeseed oil-based margarine. Rapeseed oil is similar in composition to olive oil, though it is composed of slightly higher amounts of linolenic acids.
The study was terminated early due to significant benefit found at intermediate analysis at ~4 years. Death occurred in 34/303 (8.0%) in the control group versus 14/302 (4.6%) in the Mediterranean diet group (p=0.03). There were new cancers discovered in 17/302 (5.6%) of the control group versus 7/302 (2.3%) in the Mediterranean diet group (p=0.05). There were 33 (8.2%) non-fatal MI’s in the control group versus 8 (2.6%) in the Mediterranean diet group.
Patients who developed cancer in both groups had much higher rates of smoking. There were no significant differences in the 2 groups in terms of tobacco use, medications used (including anti-lipids), exercise, weight, blood pressure, and psychosocial factors that were addressed in a separate paper.2 The only significant difference found between the control and experimental groups was in nutrient intake. Interestingly, there was no significant difference between the groups in terms of serum cholesterol, triglycerides, or HDL at the end of the study.
Caveats: It is not certain to what degree each diet was followed in each group, though surveys and serum samples of the experimental group point to strong Mediterranean diet adherence. The authors specifically tried to evaluate for a placebo effect from the diet counseling via surveys and concluded there was none. The fact that the patients were 90% male makes it harder to draw conclusions about the possible impact of diet in women.
The magnitude of this study’s results is astonishing. To compare saving a life post-heart attack with this diet (NNT= 30) and with statins (NNT=83) suggests that diet is nearly three times more powerful as a life-saving tool. A few factors make this particularly remarkable. Cancers were also reduced, while some authors have raised concerns about statins increasing cancer risk (without supporting evidence in the industry-sponsored trials to date). Imagine that the control group had been following a typical dietary pattern rather than the AHA recommended diet; the size of the effect could be even greater. Finally, the study suggests that cholesterol, which was not reduced by the Mediterranean diet, may not be as important a dietary consideration for heart disease prevention as currently thought and practiced.
It is difficult to make sweeping statements from a single study, but given the existing data and lack of harms the Mediterranean diet seems beneficial and should be strongly recommended at this time.
Author: Joshua Quaas, MD
Published/Updated: September 17, 2010
