Although evidence is scarce, most researchers agree that the “Paleo diet” had no dairy or grains and was high in meat, fish or shellfish, fruits, greens, roots, and nuts.
Studies on the effects of Paleo-type diets in modern people remain scarce, but evidence suggests they probably benefit weight control and overall health.
The traditional Mediterranean diet enjoys far more evidence of its health benefits, if only because it’s been studied much longer.
For example, see “Mediterranean Diet Cut Heart Deaths by 30%”, “Mediterranean Diet Affirmed by New Analysis”, and “Mediterranean Diet Bests Low-Fat Rival in Heart-Health Face-Off”.
While they vary, traditional Mediterranean diets share two relevant attributes:
- Rich in anti-inflammatory, antioxidant foods: Fish, vegetables, culinary herbs, and extra virgin olive oil. (Note: Refined, “pure” grade olive oil lacks the potent antioxidants in unrefined “extra virgin” oil and is far less heart-healthy.)
- Low in pro-inflammatory foods: Red meat, refined grains, and omega-6-rich cooking oils (e.g., corn, soy, safflower, sunflower, cottonseed) and processed foods.
Some researchers hypothesize that low-fat diets are counterproductive because they lack anti-inflammatory omega-3 fats and the anti-inflammatory antioxidants in extra virgin olive oil … both clinically shown to support cardiovascular health.
The evidence suggests that half of all diabetes cases could be prevented with weight loss achieved via lower-calorie diets and increased physical activity (Gillies CL et al. 2007).
In fact, lifestyle modification performs better than drugs such as metformin (Glucophage) or rosiglitazone (Avandia) for diabetes prevention (Knowler WC et al. 2002; Gerstein HC et al. 2006; Phung OJ et al. 2011)
However, over time, relatively few people at risk manage to achieve and maintain weight loss and engage in substantial exercise.
And until now there’s been little clinical study of a key question: can diet changes that do not lead to weight loss and do not include calorie restriction or more physical activity prevent diabetes?
For the first time, a clinical trial suggests that a Mediterranean diet plus added extra virgin olive oil (EVOO) can dent the risk of diabetes … even when people don’t lose weight or exercise more.
Mediterranean diet plus extra virgin olive oil (EVOO) deterred diabetes
For their study, Spanish researchers recruited 3,541 men and women aged 55 to 80 and free of diabetes for a relatively long four-year clinical trial (Salas-Salvadó J et al. 2014).
All of the participants had at least three cardiovascular risk factors, which also placed them at risk for diabetes.
The Spanish scientists randomly assigned them to one of three diets:
- Low-fat control diet
- Mediterranean diet, plus two ounces of extra virgin olive oil (EVOO) daily
- Mediterranean diet, plus one ounce of mixed nuts (1/2 oz walnuts, 1/4 oz almonds, 1/4 oz hazelnuts) daily
The participants were neither asked nor advised to exercise or to cut their usual calorie intake.
Dietitians gave personalized advice to participants assigned to either Mediterranean diet:
- Nut intake (added-nuts group only)
- EVOO intake (added-EVOO group only)
- Eat white meat instead of red or processed meat
- Raise intake of vegetables, fruits, legumes (beans), and fish
- Reduce alcohol intake, other than wine in moderation with meals.
- Avoid butter, fast food, sweets, pastries, or sugar-sweetened beverages.
- Dress dishes with “sofrito” sauce (tomato, garlic, onion, and spices simmered in olive oil).
Quarterly, the dietitians held individual and group trainings on typical Mediterranean foods, seasonal shopping lists, and meal plans … and they provided recipes to each group.
The participants on the low-fat control diet also got personalized advice and were invited to group sessions. Their diet plan called for substantial cuts to intake of animal and vegetable fats alike.
In each group session, dietitians administered a questionnaire to assess each volunteer’s adherence to their assigned diet, so that personalized coaching could be provided as needed.
Encouragingly, both of the Mediterranean diets beat the control diet:
The risk reduction for the Mediterranean diet with added EVOO was statistically significant … but it was not statistically significant for the Mediterranean diet with nuts.
Importantly, the results were calculated after accounting for the health and socioeconomic factors known to affect the risk of diabetes.
Eight years ago, Professor Ramón Estruch, M.D., of the University of Barcelona co-authored a similar 2006 trial testing Mediterranean diets plus EVOO or nuts against heart disease, with similar success (Estruch R et al. 2006).
As told The New York Times, “The strength of our study is that it has a large number of participants with a long follow-up and a randomized design. The diet works by itself without considering physical activity or changes in weight, which were insignificant between groups.” (NYT 2014)
- Estruch R, Martinez-Gonzalez MA, Corella D, Salas-Salvado J, Ruiz-Gutierrez V, Covas MI, Fiol M, Gomez-Gracia E, Lopez-Sabater MC, Vinyoles E, Aros F, Conde M, Lahoz C, Lapetra J, Saez G, Ros E; PREDIMED Study Investigators. Effects of a Mediterranean-style diet on cardiovascular risk factors: a randomized trial. Ann Intern Med. 2006 Jul 4;145(1):1-11. Summary for patients in: Ann Intern Med. 2006 Jul 4;145(1):I11. Estruch R, Ros E, Salas-Salvadó J, Covas MI, D Pharm, Corella D, Arós F, Gómez-Gracia E, Ruiz-Gutiérrez V, Fiol M, Lapetra J, Lamuela-Raventos RM, Serra-Majem L, Pintó X, Basora J, Muñoz MA, Sorlí JV, Martínez JA, Martínez-González MA; the PREDIMED Study Investigators. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013 Feb 25. [Epub ahead of print] Gerstein HC, Yusuf S, Bosch J, Pogue J, Sheridan P, Dinccag N, et al; DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication) Trial Investigators. Effect of rosiglitazone on the frequency of diabetes in patients with impaired glucose tolerance or impaired fasting glucose: a randomised controlled trial. Lancet. 2006;368:1096-105. [PMID: 16997664] Gillies CL, Abrams KR, Lambert PC, Cooper NJ, Sutton AJ, Hsu RT, et al. Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis. BMJ. 2007;334:299. [PMID: 17237299] Hadziabdić MO, Bozikov V, Pavić E, Romić Z. The antioxidative protecting role of the Mediterranean diet. Coll Antropol. 2012 Dec;36(4):1427-34. Serra-Majem L, Roman B, Estruch R. Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutr Rev. 2006 Feb;64(2 Pt 2):S27-47. Review. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, et al; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346:393-403. [PMID: 11832527] Phung OJ, Sood NA, Sill BE, Coleman CI. Oral anti-diabetic drugs for the prevention of Type 2 diabetes. Diabet Med. 2011;28:948-64. [PMID: 21429006] Salas-Salvadó J et al. Prevention of Diabetes With Mediterranean Diets: A Subgroup Analysis of a Randomized Trial. Ann Intern Med. 2014;160(1):1-10-10. doi:10.7326/M13-1725 Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010 Nov;92(5):1189-96. doi: 10.3945/ajcn.2010.29673. Epub 2010 Sep 1. Review. Tyrovolas S, Panagiotakos DB. The role of Mediterranean type of diet on the development of cancer and cardiovascular disease, in the elderly: a systematic review. Maturitas. 2010 Feb;65(2):122-30. doi: 10.1016/j.maturitas.2009.07.003. Epub 2009 Aug 4. Review. Urpi-Sarda M, Casas R, Chiva-Blanch G, Romero-Mamani ES, Valderas-Martínez P, Arranz S, Andres-Lacueva C, Llorach R, Medina-Remón A, Lamuela-Raventos RM, Estruch R. Virgin olive oil and nuts as key foods of the Mediterranean diet effects on inflammatory biomakers related to atherosclerosis. Pharmacol Res. 2012 Jun;65(6):577-83. doi: 10.1016/j.phrs.2012.03.006. Epub 2012 Mar 18. Review.