A Mediterranean diet

Diet can improve life, say Dr Toni Steer and Holly Margerison

The traditional diet of the Mediterranean countries includes a number of elements that are not part of the traditional diet in the UK.

This diet has been shown to increase longevity and improve quality of life. It may also lower the risk of chronic diseases including metabolic disorders, cardiovascular disease (CVD) and some cancers.

Reduced CVD
The beneficial effect of the Mediterranean diet coupled with a healthy lifestyle is reflected in the longevity of people living in Mediterranean regions and their low incidence of neoplasms.

A study that tested the effect of a Mediterranean-style diet rich in alpha-linolenic acid on the rate of coronary recurrences found a major reduction in the risks. After an average follow-up of 46 months, patients following the diet had a 50-70 per cent lower risk of recurrent heart disease, confirming its cardioprotective effect.

Most studies describing the Mediterranean diet and its effect on health outcomes have been observational. It is therefore difficult to separate out the effects of individual components of the diet from the effects of the dietary pattern as a whole. But there is evidence that several individual components of the diet provide health benefits in their own right.

Monounsaturated fats
Olive oil is a concentrated dietary source of monounsaturated fat (MUFA) and is associated with a lower risk of lipid peroxidation, and decreased free-radical production.

Unlike saturates, MUFAs do not raise blood cholesterol and unlike polyunsaturated fatty acids, they do not lower HDL cholesterol.

There is good evidence that reductions in LDL cholesterol levels and associated reductions in CVD risk can be achieved by substituting saturated fats with MUFAs.

Fish is frequently eaten instead of meat in Mediterranean regions and oily fish are an important source of omega-3 fatty acids. These have been shown to lower triglycerides and regulate haemostatic factors providing an anti-inflammatory effect that stabilises the lining of blood vessels and protects against cardiac arrhythmias.

Fruits and vegetables
The high intake of fruits and vegetables characteristic of the Mediterranean diet provides vitamins, fibre and antioxidants that can reduce the risk of CVD and improve heart health. There is also some evidence that high vegetable consumption reduces the risk of colorectal cancer.

Although it is believed to be the antioxidants that protect the body from free-radical damage and therefore reduce the risk of cancer, intervention trials using antioxidant supplements have not shown positive benefits.

It is likely that a range of other compounds found in fruit and vegetables, including non-starch polysaccharides, contribute to their protective effect.

High fibre
Bread is another important part of the Mediterranean diet. Cereals and cereal products provide dietary fibre, which is important for GI health, but also have important cholesterol-lowering effects. Even white bread contains fibre and whole grain varieties may bring additional benefits.

One study found a 20 per cent lower risk of CHD in the highest quintile of wholegrain intake compared with the lowest quintile. This is probably the effect of the high vitamin, mineral and other phytonutrient content of wholegrain foods.

Moderate alcohol intake
Regular alcohol consumption is a characteristic of the Mediterranean diet. It is usually drunk as part of a meal, and this may have a different effect on the body than drinking without food.

A light intake of alcohol is associated with a reduced risk of heart disease. Wine has been shown to reduce the risk of thromboses. Red wine contains flavanoids, which act as an antioxidant.

There is evidence that red wine consumption reduces CVD mortality, possibly through improved endothelial function.

Positive changes
The Mediterranean diet can be of particular benefit to patients at increased risk of CVD and, combined with an increase in physical activity levels, it could significantly improve the health of the nation as a whole.

The public health focus on reducing fat intake can distract attention from other dietary changes that could have important public health benefits.

Instead of the ever-increasing negative health messages that patients receive, the message from the Mediterranean diet is positive: increase fruit and vegetable intake; increase fish and substitute monounsaturated fat in place of saturated fat.

At the individual level, negotiating small, achievable dietary changes with patients in a stepwise manner can help facilitate a move towards a more healthy dietary pattern.

Dr Steer and Ms Margerison are nutritionists at the MRC Human Nutrition Research Unit, Cambridge.

Characteristics of the Mediterranean diet

  • Rich in monounsaturated fat.
  • Low in saturated fat.
  • Fish consumption several times a week.
  • Low to moderate consumption of dairy foods.
  • Low to moderate consumption of red meat.
  • High consumption of fruits, vegetables, cereals, pulses, nuts and seeds.
  • Moderate alcohol intake, usually with food.

REFERENCES

- Hu F, Stampfer M, Manson J et al. Dietary fat intake and the risk of coronary heart disease in women. N Engl J Med 1997; 337:1,491-9.

- Ortega R. Importance of functional foods in the Mediterranean diet. Public Health Nutr 2006; 9: 1,136-40.

- Poppitt S. Soluble fibre oat and barley b-glucan enriched products: can we predict cholesterol-lowering effects. Br J Nutr 2007; 97: 1,049-50

- Jensen M, Koh-Banerjee P, Hu F et al. Intakes of whole grains, bran and germ and the risk of coronary heart disease in men. Am J Clin Nutr 2004; 80: 1,492-9.

- Khan N, Leeds D, Douthwaite J et al. Comparison of red wine extract and polyphenol constituents on endothelin-1 synthesis by cultural endothelial cells. Clin Sci (Lond) 2002; 103 Suppl 48: 72S-75S.

- Trichopoulou A, Costacou T, Bamia C et al. Adherence to a Mediterranean diet and survival in a Greek population. N Engl J Med 2003; 348: 2,599-608.

- Serra-Majem L, Roman B, Estruch R. Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutr Rev 2006; 64: S27-47.

- De Lorgeril M, Salen P, Martin J et al. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation 1999; 99: 779-85.

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