In general, I’m unconvinced about fad diets, unless there is some really powerful published evidence in support. And those are rare. However, I think that there is some good evidence that the Mediterranean diet may be valuable to improving outcomes for several outcomes like cardiovascular diseases. Now we see that there is moderate evidence that the Mediterranean diet could add years to the life of the elderly.
There is a new study published that examines whether the Mediterranean diet could prolong the life of the elderly. Let’s take a look.
The Mediterranean diet
The Mediterranean diet is a diet that is common to the eating habits of people living in areas of the Mediterranean, including Greece, Southern Italy, and Spain. The diet generally includes proportionally high amounts of olive oil, legumes, unrefined grains, nuts, fruits, and vegetables. It also includes moderate to high consumption of fish, moderate consumption of dairy products (generally, cheese and yogurt), moderate wine consumption, and low consumption of other types of meat foods.
During the 1940s and 50s, scientists observed that people who consumed these diets seem to be objectively healthier (broadly defined) than other populations that ate other types of diets that included refined grains and non-fish meats.
I’ve previously written about this diet with respect to cardiovascular diseases, where a very large study seemed to show positive benefits, although there were some issues in the original research that was eventually corrected. There is also some moderate to good evidence that the diet has a benefit in preventing Alzheimer’s disease, lowering risks for some cancers, and improving blood glucose control for type 2 diabetics.
Mediterranean diet adoption for elderly
In a new study published in the British Journal of Nutrition, Marialaura Bonnacio et al. undertook a prospective cohort study, considered a moderate quality type of research study, to examine the health and diet of 5200 individuals aged 65 and over from the Molise region of Italy. These individuals were recruited as part of a larger study between 2005 and 2010. They were followed until 2015.
Participants completed a food survey that inquired about their diet during the year prior to enrolling in the study. Each survey was scored on how close they adhered to a Mediterranean diet (from a low score of 0 to a high of 9). One of the weaknesses of a cohort study is the reliance upon surveys and questionnaires, which can vary in quality depending on the participant. However, larger numbers of participants can mitigate the quality of the surveys.
Here are some of the key results:
- Individuals who stuck most closely to the “ideal” Mediterranean diet were also more likely to undertake more physical activity in their free time. Of course, this alone could have a large influence on health outcomes.
- When confounding factors such as age, sex, activity levels, socioeconomic status, smoking, and BMI were taken into account, individuals with a high adherence to the diet (scoring 7-9 on the scale mentioned above) had a 25% lower risk of any cause of death than those who only scored 0-3.
- In fact, a one-point increase in adherence to the diet was linked to about a 6% drop in the risk of death from any cause.
- The researchers found no significant links for specific causes of death, such as cancer or cardiovascular disease. There was a weak correlation between the diet and reduced risk of coronary artery or cerebrovascular disease mortality.
- The researchers also attempted to determine if removing certain components of the Mediterranean diet were linked to increases or reductions in risk. Although the statistical quality was weak, increases in saturated fats (or a reduction in consumption of fish), reduction in a moderate amount of alcohol, a reduction in cereals, all appear to reduce the size of the benefit of the diet.
There are some limitations to this study. First, cohort studies cannot establish a causal link between the Mediterranean diet and reduction in mortality in the elderly. Larger studies would be required to provide stronger evidence of causality. Second, it is possible that those that are already healthier better adhere to diets like this one. Lastly, as I mentioned above, self-reporting surveys, as used in this study, are prone to memory errors.
However, the researchers also included a meta-analysis of another six unrelated studies that also focused on the elderly. Those studies suggested a 5% reduction in mortality risk for every one point better adherence to the Mediterranean diet.
The researchers concluded that:
a prospective cohort study and a meta-analysis showed that closer adherence to the MD (Mediterranean diet) was associated with prolonged survival in elderly individuals, suggesting the appropriateness for older persons to adopt/preserve the MD to maximise their prospects for survival.
Overall, this is a lot of moderate evidence that adopting and adhering to a Mediterranean diet can reduce the rate of mortality for elderly individuals. It’s also possible that starting a healthy lifestyle, including this diet, at a young age would provide even a greater benefit.
Again, there are some weaknesses to this type of study, and it cannot establish a causal effect between the diet and lowered mortality risk for the elderly. However, this study, along with several others, are strongly suggestive of a benefit of the Mediterranean diet for individuals.
- Bonaccio M, Di Castelnuovo A, Costanzo S, Gialluisi A, Persichillo M, Cerletti C, Donati MB, de Gaetano G, Iacoviello L. Mediterranean diet and mortality in the elderly: a prospective cohort study and a meta-analysis. Br J Nutr. 2018 Aug 30:1-14. doi: 10.1017/S0007114518002179. [Epub ahead of print] PubMed PMID: 30157978.
- Dinu M, Pagliai G, Casini A, Sofi F. Mediterranean diet and multiple health outcomes: an umbrella review of meta-analyses of observational studies and randomised trials. Eur J Clin Nutr. 2018 Jan;72(1):30-43. doi: 10.1038/ejcn.2017.58. Epub 2017 May 10. Review. PubMed PMID: 28488692.
- Esposito K, Maiorino MI, Bellastella G, Chiodini P, Panagiotakos D, Giugliano D. A journey into a Mediterranean diet and type 2 diabetes: a systematic review with meta-analyses. BMJ Open. 2015 Aug 10;5(8):e008222. doi: 10.1136/bmjopen-2015-008222. Review. PubMed PMID: 26260349; PubMed Central PMCID: PMC4538272.
- Lavalette C, Adjibade M, Srour B, Sellem L, Fiolet T, Hercberg S, Latino-Martel P, Fassier P, Deschasaux M, Kesse-Guyot E, Touvier M. Cancer-Specific and General Nutritional Scores and Cancer Risk: Results from the Prospective NutriNet-Santé Cohort.Cancer Res. 2018 Aug 1;78(15):4427-4435. doi: 10.1158/0008-5472.CAN-18-0155. Epub 2018 Jul 26. PubMed PMID: 30049821.
- Solfrizzi V, Panza F, Frisardi V, Seripa D, Logroscino G, Imbimbo BP, Pilotto A. Diet and Alzheimer’s disease risk factors or prevention: the current evidence. Expert Rev Neurother. 2011 May;11(5):677-708. doi: 10.1586/ern.11.56. Review. PubMed PMID: 21539488.
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