Type 2 diabetic? Stay off medication longer with a Mediterranean-style diet

Outcomes in a small portion of a much larger trial suggest that a Mediterranean style diet supplemented with extra virgin olive oil may help those with type 2 diabetes avoid having to take glucose-lowering medication for longer than either a Mediterranean-style diet supplemented with mixed nuts or a low-fat diet.

We've discussed outcomes from this large-scale, long-term study before: it's called the PREDIMED trial (Prevencion con Dieta Mediterranea). Briefly, between October 2003 and June of 2009 nearly 7,500 Spanish men and women between 55 and 80 years of age and without heart disease were randomly assigned to one of three diets: a Mediterranean-style diet supplemented with extra virgin olive oil, a Mediterranean-style diet supplemented with mixed nuts, or a control diet that simply recommended that the assigned participants reduce their overall fat intake.

The participants responded to medical, dietary, and demographic questionnaires at the start of the study, repeating the questionnaires on a yearly basis. From the initiation of the study those assigned to a Mediterranean-style diet received counseling on a quarterly basis on how to follow a Mediterranean-style diet, while those assigned to a low-fat diet received initial training but not quarterly counseling sessions until at least 3 years after starting the study.

For their analysis, the authors of this study limited their research to those participants who had been diagnosed with type 2 diabetes prior to enrolling in the study: about 3,200 people (Diabetes Care 2019;42:1390-1397). They had one simple question: after enrolling in the study, how long was it until the participant had to start taking glucose-lowering medication?

The authors took into account not only the usual demographic and dietary variables, they also took into account recently-revealed irregularities in the study's randomization.

They found that compared to those on the low-fat eating plan, those who followed either type of Mediterranean-style diet were 9% less likely to need to start glucose-lowering medication, and 13% less likely to need to start long-term insulin treatment.

When considering each Mediterranean-style diet alone, those whose diet was supplemented with about 4 Tablespoons of olive oil per day were 22% less likely to need to start medication, while those who diet was supplemented with an ounce of mixed nuts per day were 11% less likely to need to start medication.

What this means for you

What's particularly significant about this study is that the participants were not instructed to cut calories or to increase their physical activity: they simply changed their style of eating for the long term and avoided having to take glucose-lowering medication for longer than if they had gone on a low-fat diet.

Why were the results better for those on the Mediterranean-style diet supplemented with olive oil rather than nuts? The authors of this study could note only that the added extra virgin olive oil in those participants' diets assigned to that group represented about 22% of their total calories, while only 8% of the calories came from the nuts in the diet of those assigned to that group. Might more nuts have the same effect as the olive oil? We can't be sure. Either way, this study adds to the evidence for a Mediterranean-style diet being best for type 2 diabetics.

First posted: August 7, 2019