Consuming a Mediterranean diet can help people live longer, reported six newspapers (11th December 2007). The newspapers were generally accurate in their reports of a large cohort study, which looked at the relationship between diet and mortality in older people.
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Six newspapers (1-6) on 11th December 2007 reported that consuming a Mediterranean diet can cut the risk of dying early.
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The reports are based on a prospective cohort study of 380,296 people aged between 50 and 71 years, who completed a survey of their dietary habits and were then followed-up over a five-year period (7). The study found that significantly fewer people who most closely followed a Mediterranean-type diet died of cancer, heart disease or all causes, when compared with those who least closely followed such a diet.
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The newspapers generally provided accurate reports of the study. The article in the Daily Mail (1) reported a total of 21,541 deaths, though in fact only 12,105 people died during the five-year follow-up.
Evaluation of the evidence base for the relationship between adherence to Mediterranean dietary patter and mortality in a US population
Where does the evidence come from?
The research was led by Dr Panagiota N. Mitrou and colleagues of the National Cancer Institute, Bethesda, Maryland, USA.
What were the authors' objectives?
To investigate the relationship between adherence to the Mediterranean dietary pattern and mortality in a US population.
What was the nature of the evidence?
The evidence came from a prospective cohort study of 380,296 people (214,284 men, 166,012 women) aged between 50 and 71 years. All participants completed a survey on their demographic and health-related behaviours, were free of chronic disease at study entry and had an energy intake in the normal range. Participants also completed a 124-item food frequency questionnaire on their dietary habits. For the period 1995/96 to 2001, all deaths and causes of death in the study group were verified using official sources.
What were the factors of interest?
Individual participants were scored on their conformity to the Mediterranean dietary pattern. On the basis of this score, participants were then divided into three groups according to their level of conformity (highest, medium, lowest).
The authors analysed the association between conformity with the Mediterranean diet and mortality (all-cause mortality and mortality from cardiovascular disease (CVD), cancer and other causes). The statistical analysis was adjusted for various potential risk factors, including: age, total energy consumption, smoking history, level of education, body mass index (BMI), level of physical activity, race, marital status, and (in women) menopausal status.
What were the findings?
During the five years of follow-up there were a total of 12,105 deaths (5985 due to cancer, 3451 due to CVD).
Comparing the highest and lowest groups, higher conformity with the Mediterranean dietary pattern was associated with a statistically significant reduction in all-cause mortality (23% average reduction in men, 22% in women), cancer mortality (21% in men, 14% in women) and CVD mortality (24% in men, 21% in women).
This association remained when the authors conducted sensitivity analyses and subgroup analyses, with the exception of the subgroup of participants with a BMI of 30 or higher who had never smoked.
What were the authors' conclusions?
The authors concluded that their study provided strong evidence that higher conformity with the Mediterranean dietary pattern is associated with lower all-cause and cause-specific mortality.
How reliable are the conclusions?
The conclusions are based on a large and generally well conducted prospective cohort study. Attempts were made to follow-up all the participants who were included in the study and important factors that may have influenced mortality were taken into account during the analysis. However, with this kind of study design there remains potential for confounding (e.g. smoking was associated with decreased conformity with the Mediterranean dietary pattern, meaning that the pattern of outcomes might be at least partly attributable to smoking).
Participants' dietary habits appear to have only been measured at baseline but not during follow-up, so it is possible that participants changed their dietary habits over time. However, it is unlikely that this would occur to the extent that would negate the overall findings of the study.
The authors' conclusions appear appropriate given the evidence presented, though it should be noted that the study was limited to a population of older people with no history of chronic illness (e.g. cancer, heart disease, emphysema, diabetes) and that it did not look at the relationship between diet and the overall occurrence of cancer, heart disease or any other illness.
Systematic reviews
Information staff at CRD searched for systematic reviews relevant to this topic. Systematic reviews are valuable sources of evidence as they locate, appraise and synthesize all available evidence on a particular topic.
There were no related systematic reviews identified on the Cochrane Database of Systematic Reviews (CDSR). One related systematic review was identified on the Database of Abstracts of Reviews of Effects (DARE)(8).
References and resources
1. How the Mediterranean diet could help you live longer. Daily Mail, 11 December 2007, p35.
2. Mediterranean diet, exercise are key to long life. Daily Telegraph, 11 December 2007, p4.
3. Mediterranean diet prolongs life. The Independent, 11 December 2007, p6.
4. A Med-style diet is key to living longer. Daily Express, 11 December 2007, p21.
5. Med diet is tops. The Sun, 11 December 2007, p6.
6. Mediterranean diet cuts mortality rates, says study. The Guardian, 11 December 2007, p12.
7. Mitrou PN, Kipnis V, Thiébaut ACM, Reedy J, Subar AF, Wirfält E, Flood A, Mouw T, Hollenbeck AR, Leitzmann MF, Schatzkin A. Mediterranean dietary pattern and prediction of all-cause mortality in a US population: results from the NIH-AARP diet and health study. Archives of Internal Medicine, 2007;167(22):2461-2468.
8. Serra-Majem L, Roman B, Estruch R. Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutrition Reviews 2006;64(2 Supplement):S27-S47. [Provisional DARE Abstract]
Consumer information
NHS Direct - Diet recommendations
Previous Hitting the Headlines summaries on this topic
Mediterranean diet halves risk of lung disease. Hitting the Headlines archive, 16 May 2007.
Further information about Hitting the Headlines
Further information about Hitting the Headlines, together with selected relevant links, can be found at http://www.library.nhs.uk/hth/.
