The Cardiodiet Trial

Medelhavskost
Mediterranean food with low carbohydrate levels.

Is a Mediterranean diet with reduced carbohydrate content a better choice than traditional low-fat diet for patients with coronary heart disease?

After treatment at the coronary care unit (CCU) for ischemic heart disease (angina pectoris with or without myocardial infarction, IHD) patients are usually helped at a specialized cardiovascular rehabilitation unit which includes specialized nurses, physical therapists and dieticians. A great majority of patients treated at CCU have either pre-diabetes or frank diabetes in Sweden.

There are no modern studies on the best dietary advices in IHD to be given in combination with current advanced standard medication and other invasive treatments of this severe condition. The 10 year long LOOK-Ahead trial of patients with type 2 diabetes could not show any reduction of CVD by the combination of increased physical activity and weight reduction based on a low-fat diet (LFD) in a randomized setting in 5145 patients with type 2 diabetes.

On the other hand, a study of patients at high risk for CVD showed lowered incidence of CVD with a Mediterranean type of diet when this was compared to traditional LFD, in a setting without aim to lose weight. The Mediterranean diet also halved the risk to develop diabetes in a subset of patients that were diabetes-free at baseline, compared with LFD.

We have published three papers from a randomized study of patients with type 2 diabetes in which a low carbohydrate diet, 20 energy % (E%) from carbohydrates was compared with a traditional low-fat diet (55-60E% from carbohydrates) for two years with the goal to achieve weight reduction. Both diets reduced body weight similarly (-4kg) after 6 months but only the low-carbohydrate diet (LCD) reduced HbA1c and concomitantly allowed a 29% reduction of insulin doses. We have also published increased quality of life (QOL) and diminished low-grade inflammation in the LCD group compared with LFD.

Comparison between a Mediterranean diet and traditional Low Fat Diet

Kostråd Medelhavskost - häftenPhoto credit: Emma Busk Winquist

We aim to compare a diet which is a combination of the LCD we have already tested and the Mediterranean diet described above with a traditional LFD. The new test-diet should have an energy % from carbohydrates between 25-30% and participants should be encouraged to consume olive oil, nuts and legumes.

The controls will be informed to eat LFD with 55-60 E% from carbohydrates with emphasis on potatoes, grain or rice combined with choosing low-fat dairy products. There is no general aim to reduce weight in either group.

As in our study of type 2 diabetes, above, dieticians will provide patients with folders containing suitable recipes and an easily accessible central dietician will also be ready to answer questions and queries for both groups. Every 3 months participants will be encouraged to attend group meetings, as in our previous study.

Outcome

The outcome will be diabetes incidence and/or glycaemic control by HbA1c. Secondary outcomes are QOL (questionnaires) and CVD incidence. Food patterns (compliance) will also be assessed by questionnaires and all variables will be assessed yearly. The study setting is primarily Linköping, Norrköping and Jönköping. Assuming a 50% participation-rate we will recruit ca 400 participants/year, i.e. 1200 in 3 years. The study has 90% power to detect a hazard ratio 0.75 of either diabetes incidence or lowered CVD recurrence of the Mediterranean diet. It makes a large difference for the patient to develop diabetes, or not, and in patients with prevalent diabetes it is crucial to achieve target HbA1c.

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