A number of traditional diets have been identified and researched because they may protect from chronic disease. Of these, the Mediterranean diet is perhaps the most well known. Generally, traditional diets are high in plant based foods such as whole grains, fibre, pulses, legumes and antioxidant rich fruits and vegetables, and contain low levels of processed meats, refined vegetable oils and refined carbohydrates. The mechanism by which traditional diets are able to reduce the risk of chronic disease is not fully understood, but it is though they are effective because they decrease systemic inflammation through a combination of reduced glycaemic index, a beneficial omega 3 to omega 6 fatty acid ratio, and through low intakes of arachidonic acid (AA, C20:4 (n-6)). In contrast, the typical Western diet is thought to stimulate chronic inflammation and oxidative stress that can lead to the development of cancer, diabetes, cardiovascular disease, metabolic syndrome and obesity.
High intakes of linoleic acid (LA, C18:2 (n-6)) rich vegetable oil, combined with low intakes of omega 3 oils such as alpha-linolenic acid (ALA, C18:3 (n-3)) and eicosapentanoic acid (EPA, C20:5 (n-3)), increases production of the pro-inflammatory eicosanoids and results in inflammation, platelet aggregation, thrombosis and oxidative stress. This process is exacerbated by high insulin levels because insulin can activate the delta 5-desaturase and delta 6-desaturase enzymes necessary for the formation of the inflammatory eicosanoids. The high vegetable oil, high refined carbohydrate, low fatty fish diets of the Western nation are thus pro-inflammatory diets that lead to long term low-level chronic inflammation that increases the risk of lifestyle diseases. In addition, arachidonic acid (AA, C20:4 (n-6)) rich diets, such as might occur with high intakes of red meat, provide further precursor molecules for the inflammatory pathways.
The people who inhabit the southern islands of Japan are renowned for their longevity, with the island of Okinawa having the longest life expectancy within Japan. This longevity may related to the diet of the population, who consume a relatively low calorie, high polyphenol, vitamin and mineral rich diet. The staple foods of the Okinawan people is a vegetable dish called champuru, which contains bitter melon, and is usually accompanied by konbu seaweed and konnyaku. A miso soup is also consumed and this contains water, miso, seaweed, tofu, sweet potato and green leafy vegetables. Smaller servings of fish, or lean meat with herbs often accompany these staple foods. Jasmine tea or small amounts of millet brandy (awamori) can also be drunk with meals. The Okinawan diet is therefore rich in antioxidants, omega 3 fatty acids and contains moderate amounts of alcohol, all of which have been shown to protect from disease.
As with the Greek population, the younger generations of the Okinawan people have deviated from the traditional diets as Western influence has spread following the Second World War. As a result of including Western foods into their diets, the younger generations of the Okinawan islanders have increased rates of Western diseases. One such change is the rise in the consumption of bread and rice, in combination with a fall in the consumption of the sweet potato, a staple food of the traditional Okinawan diet. The sweet potato is particularly rich in antioxidants such as vitamin C, vitamin E and polyphenols, and has a low glycaemic index. Introduction of refined rice and bread as well as other refined carbohydrates has been reported to cause increases in disease rates in other native populations, which suggests that these foods maybe a major contributor to the lifestyle diseases of the West.
RdB
