A Mediterranean diet high in fish, seafood and cereals and low in dairy products was not found to be linked to longer life, but this could be because these groups include a lot of different foods with different effects and the low numbers of people consuming fish and seafood in the sample.
The study was the work of Professor Dimitrios Trichopoulos at the Harvard School of Public Health in Boston, Massachusetts in the US, together with professor Antonia Trichopoulou and Dr Christina Bamia from the University of Athens Medical School, and is published in the 23 June issue of BMJ.
A lot of studies have made the headlines in recent years with findings that show strong links between following a Mediterranean diet and longer life, but this is the first to look inside the diet and examine links between particular foods and longer life.
For the study Trichopoulos and colleagues used data covering over 23,000 men and women who took part in the Greek section of the European Prospective Investigation into Cancer and Nutrition (EPIC) study.
The participants filled in questionnaires about their diet and lifestyle at the start of the study and then were interviewed periodically for about 8.5 years afterwards. Participants were also asked about their health, whether they smoked, how physically active they were, and whether they had ever been diagnosed with cancer, diabetes or heart disease.
Diets were scored from 0 to 10 depending on how closely they followed a traditional Mediterranean diet.
The main outcome measure was death from all causes.
The results showed that after a mean follow up of 8.5 years:
- 652 deaths from any cause had occurred among 12,694 participants with Mediterranean diet scores between 0 and 4.
- 423 deaths from any cause had occurred among10,655 participants with Mediterranean diet scores of 5 or more.
- After taking into account potential confounders, there was a statistically significant reduction in deaths among participants who stuck to a Mediterranean.
- For every two units of increase in the score the adjusted mortality ratio was 0.864 (95 per cent confidence interval ranged from 0.802 to 0.932).
- The individual foods that most contributed to this effect were: alcohol, ie ethanol (23.5 per cent), low consumption of meat and meat products (16.6 per cent), high consumption of vegetables (16.2 per cent), high consumption of fruits and nuts (11.2 per cent), high ratio of monounsaturated to saturated fats (10.6 per cent) and high consumption of pulse foods (9.7 per cent).
- High consumption of cereals and low consumption of dairy food had minimal effects, while high consumption of fish and seafood was linked to a non-significant increase in death rates.
"The dominant components of the Mediterranean diet score as a predictor of lower mortality are moderate consumption of ethanol, low consumption of meat and meat products, and high consumption of vegetables, fruits and nuts, olive oil, and legumes."
They suggested that the minimal impact of high cereal and low dairy consumption was possibly due to the fact these food groups contain many different types of of food each with different effects on health. And the non-significant effect from fish and seafood could be due to their low consumption in this sample.
"Anatomy of health effects of Mediterranean diet: Greek EPIC prospective cohort study."
Antonia Trichopoulou, Christina Bamia, and Dimitrios Trichopoulos.
doi: 10.1136/bmj.b2337 (Published 23 June 2009)
Written by: Catharine Paddock, PhD