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Scientific evidence of diets – Mediterranean diet

We are surrounded by advertisements about so-called “miracle diet”. Often these foods are beneficial to health, but individual food items cannot be considered curative. Only diet and lifestyle together can help prevent diseases. Just because some diet or recommendation is good for one person, it doesn’t mean it will fit others. Diet should be personalized as we all are different by many meanings including current health status, level of activity, etc. In the series of “Scientific evidence of diets” we will look at individual diets and their proven health benefits. Let’s start with Mediterranean diet.


WHAT IS MEDITERRANEAN DIET?


Starting in Italy thousands of years ago and spreading to other areas around the Mediterranean, like Greece, Turkey and Spain, Mediterranean diet is now promoted all over the world as successful approach for health and longevity. But in Mediterranean countries, is not just a “diet” in the way we usually think of them, but more like a lifestyle. The traditional Mediterranean diet is characterized by (Willett et al., 1995):

· a high intake of olive oil, fruit, nuts, vegetables, herbs and spices

· a moderate intake of fish and poultry, potatoes, whole grains and pulses

· a low intake of dairy products, red meat and meat products

· no processed foods, refined carbohydrates and sweets

· plenty of fresh water and some coffee or tea

· small amount of wine consumed with meals.


BENEFITS OF MEDITERRANEAN DIET


1. Improves cardiovascular health


People following the Mediterranean diet supplemented with extra-virgin olive oil or nuts have fewer instances of major cardiovascular events including stroke or heart attack (de Lorgeril et al., 1999; Serra-Majem et al., 2006; Sofi et al., 2010; Estruch et al., 2013; Estruch et al., 2018). Increased frequency of nut consumption (more than 3 servings per week) is associated with a significantly reduced risk of all-cause mortality in individuals at high cardiovascular risk (Guasch-Ferre et al., 2013). The beneficial effect on cardiovascular mortality is the same regardless of the type of nut eaten. Research has showed that these health benefits are likely due to their monounsaturated fats and omega-3 foods content (de Lorgeril and Salen, 2006). Following Mediterranean diet may also help to reduce the level of low-density lipoprotein (LDL; “bad cholesterol”). The effect is similar to the initial therapeutic dose of a cholesterol lowering drug, statin (Jenkins et al., 2003; Rees et al., 2013). Moreover, this diet helps to decrease hight blood pressure (Rees et al., 2013).


2. Fights against cardiodiabesity and metabolic syndrome


Cardiodiabesity is a hybrid term used to define and describe the well-known relationship between type 2 diabetes mellitus, obesity, metabolic syndrome and cardiovascular disease. Epidemiological and clinical trial studies have provided an evidence on the association between the adherence to a Mediterranean diet and a reduced incidence of cardiodiabesity risk (García-Fernández et al., 2014). Moreover, Mediterranean diet serves as an anti-inflammatory dietary pattern, which could help fight diseases related to chronic inflammation, including metabolic syndrome and type 2 diabetes (Babio et al., 2009). One of the reasons why Mediterranean diet can prevent diabetes is the fact that it helps to control excess insulin, a hormone that controls blood sugar levels. Furthermore, this diet is low in sugar, since the only sugar present usually comes from fruit, wine and the occasional dessert. Also, soda and sweetened drinks aren’t used. When it comes to drinks, many people drink plenty of fresh water, some coffee and red wine, too.

A Mediterranean-style diet might be effective in reducing the prevalence of the metabolic syndrome (Eposito et al., 2004). The results have shown that individuals with metabolic syndrome following Mediterranean diet have significantly reduced inflammatory markers (serum C-reactive protein and interleukins) and insulin resistance, significant decreases in waist circumference, blood pressure, blood glucose, total cholesterol and triglycerides and increase in high- density lipoprotein (HDL, “good”) cholesterol. Around 63% of the study participants has no longer metabolic syndrome when following the diet for at least two years (Eposito et al., 2004).


3. Reduces incidence of cancer


An inverse association with cancer mortality was only seen in those on Mediterranean diet and consuming three or more servings of walnuts each week (Guasch-Ferre et al., 2013). According to the European Journal of Cancer Prevention “the biological mechanisms for cancer prevention associated with the Mediterranean diet have been related to the favourable effect of a balanced ratio of omega-3 and omega-6 essential fatty acids and high amounts of fibre, antioxidants and polyphenols found in fruit, vegetables, and olive oil” (Giacosa et al., 2013).


4. Protects cognitive health

Mediterranean diet is associated with reduced risk of stroke, depression and cognitive impairment (Psaltopoulou et al., 2013). The diet is also associated with a reduced risk of developing mild cognitive impairment and Alzheimer's disease (Scarmeas et al., 2006; Singh et al., 2014). Both studies concluded the stricter the adherence to the diet, the greater the protection.


SUGGESTED MECHANISMS BEHIND THE BENEFITS OF THE MEDITERRANEAN DIET


Research data has suggested that the Mediterranean diet protects from cardiovascular disease, metabolic syndrome, type II diabetes through reduction in inflammation bought about by a variety of mechanisms including:

· reduction in plasma glucose and insulin levels

· reduction in insulin resistance and obesity

· decreased inflammation

· high content of antioxidant-rich foods

· high fibre meals

· improved omega-3 to omega-6 essential fatty acids ratio.


Support in body weight reduction is associated with the fact that Mediterranean diet:

· is plant-based diet and therefore, high in water and fibre foods

· supports moderate fat consumption

· does not include processed, sugary foods and refined carbohydrates

· include only a low alcohol consumption.


Protection from the congenital decline is associated with:

· better cardiovascular health

· reduced inflammation and oxidative stress within the brain itself

· increased micronutrients intake which supports mitochondrial health

· absence of harmful foods like processed meat or sugar.


CONCLUSIONS


A Mediterranean diet with either olive oil or nuts may reduce the risk of stroke, heart attack, and death from heart disease. I t may also help reverse metabolic syndrome. People following the Mediterranean diet experience reductions in oxidized LDL (“bad”) cholesterol. Moreover, this diet without calorie restriction appears to prevent the development of type 2 diabetes. The benefits of a Mediterranean diet are derived from the high and balanced intake of nutritious components from fruits, vegetables, legumes and nuts, without the added calories from processed foods.


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REFERENCES


· Babio N, Bulló M, Salas-Salvadó J. (2009). Mediterranean diet and metabolic syndrome: the evidence. Public Health Nutr. 12(9A):1607-1617.

· de Lorgeril M, Salen P. (2006). The Mediterranean diet in secondary prevention of coronary heart disease. Clin Invest Med. 29(3):154-158.

· de Lorgeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. (1999). Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation. 99:779-785.

· Eposito, K., Marfella, R., Ciotola, M., Di Palo, C., Giugliano, F., Giugliano, G., et al. (2004). Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome: A randomized trial. Journal of the American Medical Association. 292(12):1440-1446.

· Estruch, R., Ros, E., Salas-Salvado, J., Covas, M. I., Corella, D., et al. (2013). Primary prevention of cardiovascular disease with a Mediterranean diet. The New England Journal of Medicine, 368:1279-1290.

· Estruch R, Ros E, Salas-Salvadó J, Covas MI, Corella D, et al. (2018). PREDIMED Study Investigators. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med. 378(25):e34.

· García-Fernández E, Rico-Cabanas L, Rosgaard N, Estruch R, Bach-Faig A. (2014). Mediterranean diet and cardiodiabesity: a review. Nutrients. 6(9):3474-3500.

· Giacosa A, Barale R, Bavaresco L, Gatenby P, Gerbi V, et al. (2013). Cancer prevention in Europe: the Mediterranean diet as a protective choice. Eur J Cancer Prev. 22(1):90-95.

· Guasch-Ferre, M., Bullo, M., Martinez-Gonzalez, M. A., Ros, E., Corella, D., Estruch, R. et al. (2013). Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Medicine. 11(164).

· Jenkins, D. J. A., Kendall, C. W. C., Marchie, A. (2003). Effects of dietary lowering portfolio of cholesterol lowering foods vs lovostatin on serum lipids and C-reactive protein. Journal of the American Medical Association. 290(4):503-510.

· Psaltopoulou, T., Sergentanis, T. N., Panagiotakos, D. B., Sergentanis, I. N., Kosti, R. and Scarmeas, N. et al. (2013). Mediterranean diet and stroke, cognitive impairment, depression: A meta-analysis. Annals of Neurology. 74(4):580-591.

· Rees K, Hartley L, Flowers N, Clarke A, Hooper L, Thorogood M, Stranges S. (2013). 'Mediterranean' dietary pattern for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. (8):CD009825.

· Scarmeas N, Stern Y, Tang MX, Mayeux R, Luchsinger JA. (2006). Mediterranean diet and risk for Alzheimer's disease. Ann Neurol. 59(6):912-921.

· Serra-Majem L, Roman B, Estruch R. (2006). Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutr Rev. 64:S27-S47.

· Singh B, Parsaik AK, Mielke MM, Erwin PJ, Knopman DS, et al. (2014). Association of Mediterranean diet with mild cognitive impairment and Alzheimer’s disease: A systemic review and meta-analysis. Journal of Alzheimer’s disease. 39(2):271-282.

· Sofi F, Abbate R, Gensini GF, Casini A. (2010). Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 92:1189-1196.

· Willett WC, Sacks F, Trichopoulou A, et al. (1995). Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr. 61:Suppl:1402S-1406S

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