Entry #: 7
Date: 8 August 2017
Section: Extra-virgin olive oil and diabetes
Topic: Extra-virgin olive oil in human volunteers
Type: Human volunteer trial

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OliveNetTM Journal Club

Expert review of literature related to olives and olive oil

D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis

Title

Consumption of extra-virgin olive oil rich in phenolic compounds improves metabolic control in patients with type 2 diabetes mellitus: a possible involvement of reduced levels of circulating visfatin

Author(s)

Santangelo et. al.

Citation / Year

(1) / 2016

Keywords

Extra-virgin olive oil, phenolic compounds, type 2 diabetes, inflammation, liver function, human volunteer trial

Summary

This study represents a small trial, in terms of both number of participants (total n=11) and time (total = eight weeks with four week intervention period), aimed at investigating the effects of extra-virgin olive oil consumption in overweight people with type 2 diabetes. The purpose was to build on the knowledge that the Mediterranean diet has beneficial health effects which have been largely attributed to the consumption of extra-virgin olive oil. More specifically, the emerging evidence of the beneficial effects of the Mediterranean diet in prevention and treatment of type 2 diabetes provides a basis for this study (2, 3). In short the 11 participants (seven male, four post-menopausal females; mean age = 64.63 ± 8.52 years; BMI = 29.13 ± 2.50 kg/m2), were monitored for an eight week period. Participants were advised on lifestyle habits which included 30 minute moderate-intensity exercise (walking) per day, limited consumption of alcohol (one alcohol unit [10 g/day] for women and two alcohol units per day [20 g/day] for men), and avoidance of consumption of polyphenol-rich food (e.g. wild berries, grapes, cocoa, coffee) for the intervention period. For the first four weeks, participants were asked to replace other raw dietary fats with refined olive oil (25 mL [22 g or two tablespoons] per day). For the following four weeks, participants were asked to consume extra-virgin olive oil (containing a high phenolic content [577 mg/kg]) in place of the refined olive oil. It is important to note that the first four weeks served as the wash out period. The refined olive oil and extra-virgin olive oil, consisted of an identical fatty acid composition and vitamin E content, however, phenolic compounds were not detectable in the refined olive oi which served as a control.

Key points and implications

The authors measured a series of anthropometric and biochemical parameters related to inflammation, and liver function, at baseline, after the first four week refined olive oil period, and at the end of the eight week intervention; essentially, the aim was to determine the effects of a four week period of consumption of extra-virgin olive oil on parameters related to type 2 diabetes. The main findings indicated a reduction in body weight, BMI, fasting plasma glucose levels and HbA1c following the four week consumption of extra-virgin olive oil. Similarly, reductions in serum levels of aspartate aminotransferase and alanine aminotransferase (non-specific markers of hepatocellular [liver] damage), were observed. Only modest reductions in IL-6 and adiponectin (not reaching significance) and no changes in TNFa and apelin, were found. However, consumption of extra-virgin olive oil resulted in a significant reduction in visfatin; a direct correlation between plasma visfatin (adipocyte hormone), levels and type 2 diabetes mellitus has been indicated (4, 5). Overall, this is a relatively small study with a limited intervention period. Nevertheless, the findings do provide important and direct evidence for the potential beneficial effects of consumption of extra-virgin olive oil with high phenolic content in overweight people with type 2 diabetes.

Related publications

  1. C. Santangelo et al., Consumption of extra-virgin olive oil rich in phenolic compounds improves metabolic control in patients with type 2 diabetes mellitus: a possible involvement of reduced levels of circulating visfatin. J Endocrinol Invest 39, 1295-1301 (2016).
  2. M. Georgoulis, M. D. Kontogianni, N. Yiannakouris, Mediterranean diet and diabetes: prevention and treatment. Nutrients 6, 1406-1423 (2014).
  3. J. Salas-Salvado et al., Prevention of diabetes with Mediterranean diets: a subgroup analysis of a randomized trial. Ann Intern Med 160, 1-10 (2014).
  4. E. Adeghate, Visfatin: structure, function and relation to diabetes mellitus and other dysfunctions. Curr Med Chem 15, 1851-1862 (2008).
  5. Y. H. Chang, D. M. Chang, K. C. Lin, S. J. Shin, Y. J. Lee, Visfatin in overweight/obesity, type 2 diabetes mellitus, insulin resistance, metabolic syndrome and cardiovascular diseases: a meta-analysis and systemic review. Diabetes Metab Res Rev 27, 515-527 (2011).