Courtney R. Davis

Definition of the Mediterranean Diet; A Literature Review

Numerous studies over several decades suggest that following the Mediterranean diet (MedDiet) can reduce the risk of cardiovascular disease and cancer, and improve cognitive health. However, there are inconsistencies among methods used for evaluating and defining the MedDiet. Through a review of the literature, we aimed to quantitatively define the MedDiet by food groups and nutrients. Databases PubMed, MEDLINE, Science Direct, Academic Search Premier and the University of South Australia Library Catalogue were searched. Articles were included if they defined the MedDiet in at least two of the following ways: (1) general descriptive definitions; (2) diet pyramids/numbers of servings of key foods; (3) grams of key foods/food groups; and (4) nutrient and flavonoid content. Quantity of key foods and nutrient content was recorded and the mean was calculated. The MedDiet contained three to nine serves of vegetables, half to two serves of fruit, one to 13 serves of cereals and up to eight serves of olive oil daily. It contained approximately 9300 kJ, 37% as total fat, 18% as monounsaturated and 9% as saturated, and 33 g of fibre per day. Our results provide a defined nutrient content and range of servings for the MedDiet based on past and current literature. More detailed reporting amongst studies could refine the definition further.

A Mediterranean diet lowers blood pressure and improves endothelial function: results from the MedLey randomized intervention trial

Background: The consumption of a Mediterranean diet (MedDiet) is associated with a lower risk of cardiovascular disease. However, its impact on blood pressure and endothelial function is not clear.Objective: We sought to determine the effects of adhering to the consumption of a MedDiet for 6 mo on blood pressure and endothelial function in older, healthy Australians.Design: A total of 166 men and women aged >64 y were allocated via minimization to consume either a MedDiet (n = 85) or their habitual diet (HabDiet; control: n = 81) for 6 mo. The MedDiet comprised mainly plant foods, abundant extra-virgin olive oil, and minimal red meat and processed foods. A total of 152 participants commenced the study, and 137 subjects completed the study. Home blood pressure was measured on 5 consecutive days at baseline (n = 149) and at 3 and 6 mo. Endothelial function (n = 82) was assessed by flow-meditated dilatation (FMD) at baseline and 6 mo. Dietary intake was monitored with the use of 3-d weighed food records. Data were analyzed with the use of linear mixed-effects models to determine adjusted between-group differences.Results: The MedDiet adherence score increased significantly in the MedDiet group but not in the HabDiet group (P < 0.001). The MedDiet, compared with the HabDiet, resulted in lower systolic blood pressure (P-diet × time interaction = 0.02) [mean: -1.3 mm Hg (95% CI: -2.2, -0.3 mm Hg; P = 0.008) at 3 mo and -1.1 mm Hg (95% CI: -2.0, -0.1 mm Hg; P = 0.03) at 6 mo]. At 6 mo, the percentage of FMD was higher by 1.3% (95% CI: 0.2%, 2.4%; P = 0.026) in the MedDiet group.Conclusion: Australian men and women who consumed a MedDiet for 6 mo had small but significantly lower systolic blood pressure and improved endothelial function. This trial was registered at www.anzctr.org.au as ACTRN12613000602729.

The Mediterranean Diet and Cognitive Function among Healthy Older Adults in a 6-Month Randomised Controlled Trial: The MedLey Study

Evidence from a limited number of randomised controlled intervention trials (RCTs) have shown that a Mediterranean dietary pattern may reduce the risk of cognitive decline and enhance cognitive function among healthy older adults. However, there are currently no data in non-Mediterranean older adult populations. The present study aimed to address this gap by examining the effect of a Mediterranean dietary pattern (MedDiet) for six months on aspects of cognitive function in a randomised controlled intervention trial (the MedLey study) that extended for a duration of 18 months. In the final analysed cohort, a total of 137 men and women (mean age of 72.1 ± 5.0 years) randomly assigned to either a MedDiet or control diet (HabDiet) (i.e., habitual dietary intake), were assessed on a comprehensive neuropsychological test battery, including 11 individual tests. In multivariable-adjusted models, the MedDiet group did not perform significantly better than the HabDiet control group for executive functioning (adjusted mean differences: +2.53, 95% CI −2.59 to 7.65, p = 0.33); speed of processing (adjusted mean differences: +3.24, 95% CI −1.21 to 7.70, p = 0.15); memory (adjusted mean differences: +2.00, 95% CI −3.88 to 7.88, p = 0.50); visual-spatial ability (adjusted mean differences: +0.21, 95% CI −0.38 to 0.81, 0.48); and overall age-related cognitive performance (adjusted mean differences: +7.99, 95% CI −4.00 to 19.9, p = 0.19). In conclusion, this study did not find evidence of a beneficial effect of a MedDiet intervention on cognitive function among healthy older adults.

A mediterranean diet to improve cardiovascular and cognitive health: Protocol for a randomised controlled intervention study

The Mediterranean diet has demonstrated efficacy for improving cardiovascular and cognitive health. However, a traditional Mediterranean diet delivers fewer serves of dairy and less dietary calcium than is currently recommended in Australia, which may limit long-term sustainability. The present study aims to evaluate whether a Mediterranean diet with adequate dairy and calcium can improve cardiovascular and cognitive function in an at-risk population, and thereby reduce risk of cardiovascular disease (CVD) and cognitive decline. A randomised, controlled, parallel, crossover design trial will compare a Mediterranean diet supplemented with dairy foods against a low-fat control diet. Forty participants with systolic blood pressure above 120 mmHg and at least two other risk factors of CVD will undertake each dietary intervention for eight weeks, with an eight-week washout period between interventions. Systolic blood pressure will be the primary measure of interest. Secondary outcomes will include measures of cardiometabolic health, dietary compliance, cognitive function, assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB), psychological well-being and dementia risk. This research will provide empirical evidence as to whether the Mediterranean diet can be modified to provide recommended dairy and calcium intakes while continuing to deliver positive effects for cardiovascular and cognitive health. The findings will hold relevance for the field of preventative healthcare and may contribute to revisions of national dietary guidelines.

A Comparison of Regular Consumption of Fresh Lean Pork, Beef and Chicken on Body Composition: A Randomized Cross-Over Trial

Pork is the most widely eaten meat in the world and recent evidence shows that diets high in pork protein, with and without energy restriction, may have favourable effects on body composition. However, it is unclear whether these effects on body composition are specific to pork or whether consumption of other high protein meat diets may have the same benefit. Therefore we aimed to compare regular consumption of pork, beef and chicken on indices of adiposity. In a nine month randomised open-labelled cross-over intervention trial, 49 overweight or obese adults were randomly assigned to consume up to 1 kg/week of pork, chicken or beef, in an otherwise unrestricted diet for three months, followed by two further three month periods consuming each of the alternative meat options. BMI and waist/hip circumference were measured and body composition was determined using dual energy x-ray absorptiometry. Dietary intake was assessed using three day weighed food diaries. Energy expenditure was estimated from activity diaries. There was no difference in BMI or any other marker of adiposity between consumption of pork, beef and chicken diets. Similarly there were no differences in energy or nutrient intakes between diets. After three months, regular consumption of lean pork meat as compared to that of beef and chicken results in similar changes in markers of adiposity of overweight and obese Australian middle-aged men and women.

Older Australians Can Achieve High Adherence to the Mediterranean Diet during a 6 Month Randomised Intervention; Results from the Medley Study

Adherence to a Mediterranean diet (MedDiet) is thought to be achievable in non-Mediterranean regions, but this has yet to be investigated. We aimed to determine if an older Australian population could adhere to a MedDiet for six months. We conducted a randomised, parallel dietary intervention trial with two dietary arms: the Mediterranean diet (MedDiet) group and the habitual diet (HabDiet) control group. A 15-point Mediterranean diet adherence score and food and nutrient intakes were estimated from three-day weighed food records collected at baseline, two and four months. Erythrocyte fatty acids, serum carotenoids and urinary metabolites were assessed at baseline, three and six months. We enrolled 166 participants; 152 commenced and 137 completed the study (70 in the MedDiet group, 67 in the HabDiet group). Adherence scores were significantly higher in the MedDiet group at two months (between group difference 2.2, 95% CI 1.3, 2.9) and four months (between group difference 2.6, 95% CI 1.9, 3.3). Consumption of vegetables, fruits, fish, legumes, nuts and olive oil significantly increased in the MedDiet group compared to the control, and discretionary food intake decreased (p < 0.01). Measures of compliance including serum β-carotene, lycopene and erythrocyte monounsaturated fatty acids were significantly higher in the MedDiet group at three and six months (p < 0.05). Our results indicate that a population of older Australians can adopt a Mediterranean diet over a six month period.

A Mediterranean Diet Reduces F2-Isoprostanes and Triglycerides among Older Australian Men and Women after 6 Months

Background: Health benefits of a Mediterranean dietary pattern have been shown. However, there are few data on the effects of increased adherence to a Mediterranean diet (MedDiet) in non-Mediterranean countries.Objective: We aimed to determine whether adherence to a MedDiet would result in changes in plasma lipids, glucose and insulin, high-sensitivity C-reactive protein (hs-CRP), and F2-isoprostanes (F2-IsoPs) in an Australian population.Methods: The study was a 6-mo parallel, randomized, controlled dietary intervention trial. We recruited 166 participants aged ≥65 y. Participants were stratified on body mass index, sex, and age and assigned to receive either a MedDiet or a habitual diet (HabDiet). The primary outcome was cognitive function, reported elsewhere. As secondary outcomes, assessment of fasting total, LDL, and HDL cholesterol; triglycerides (TGs); glucose; insulin; hs-CRP; and F2-IsoPs was completed at baseline and at 3 and 6 mo. The MedDiet group followed a prescribed diet containing 15-45 mL extra-virgin olive oil/d, abundant vegetables, fruit, nuts, legumes, and whole grains, as well as moderate fish, poultry, and dairy foods. Dietary intake was measured by 3-d weighed food records at baseline and at 2 and 4 mo. Results were analyzed by using linear mixed-effects models.Results: Compared with the HabDiet, the MedDiet resulted in lower TGs at 3 mo (mean difference: -0.15 mmol/L; 95% CI: -0.23, -0.07 mmol/L; P < 0.001) and 6 mo (mean difference: -0.09 mmol/L; 95% CI: -0.18, -0.01 mmol/L; P = 0.03) and lower F2-IsoPs at 3 mo (mean difference: -103.5 pmol/L; 95% CI: -154.2, -52.7 pmol/L; P < 0.001) and 6 mo (-65.4 pmol/L; 95% CI: -117.1, -13.7 pmol/L; P < 0.001). Lipoprotein, glucose and insulin, and hs-CRP concentrations were not significantly different between groups.Conclusion: A high adherence to a MedDiet for 6 mo resulted in a significant reduction in TGs and F2-IsoPs among older Australians. This trial was registered at clinicaltrials.gov as ACTRN12613000602729.