Trial design

This trial investigated whether a Mediterranean diet improves health outcomes for women who have been treated for early stage breast cancer. The trial was the first of its kind in New Zealand and was run by the Department of Nutrition at the University of Auckland.

The study investigators aimed to test whether a Mediterranean diet helps those who’ve been treated for breast cancer to lose weight, reduce the symptoms of metabolic syndrome and lower inflammation levels in order to improve overall health.

The investigators say obesity, metabolic syndrome and inflammation are all associated with increased risk of cancer development, progression and recurrence.

A Mediterranean diet is plant-based and typically consists of a high intake of olive oil, legumes, whole grains, fruit, vegetables, nuts, seeds, fish and red wine.

The Auckland study was open to women aged 50 and over who had received treatment for breast cancer (grade 1 to 3), a body mass index (BMI) of >25 and were 3-4 months on from active treatment.

Participants could be on hormonal therapy. Exclusions included those on anti-inflammatory medication; those who drink more than 2 standard alcoholic beverages per day; those diagnosed with diabetes mellitus or those who smoke tobacco. Participants needed to provide medical information regarding their breast cancer grade. 

Study participants were randomly split into three groups. One group was asked to follow a Mediterranean diet and received dietary support and information. The treatment diet did not restrict food volumes, just altered food types. Another group followed a New Zealand healthy eating diet with dietary support and information. The third group continued with their usual diet.

Face-to-face group education for those in the first two groups occurred once-monthly, with a newsletter sent via email two weeks later.

The study ran for 12 months and body weight, blood tests, gene changes and quality of life status were measured at the start of the trial and then again when the trial ended.


Compared to the 'usual diet' control group, both the 'Mediterranean diet' and 'NZ healthy eating diet' groups lost weight, with significant decreases in body mass index (BMI) and waist circumference, and had improved blood biomarkers, such as blood lipids and blood glucose. Both diet groups showed satisfactory adherence to their diets. The researchers concluded that nutritional education and group support appears to exert beneficial effects on health in breast cancer survivors; of lesser importance is the type of diet that forms the basis of the education. 

The published results can be read here.