The Japanese diet found traditionally in Japan and its Islands, is a diet consisting of a high variety of foods. It is relatively free of saturated fats, red meats and dairy, and high in fish, vegetables, grains and fruit. Of particular importance is the high intake of phytochemicals through the consumption of green vegetables, soy and algae. The style of eating as well as the food that is eaten is also very important. The seasons, tradition, religion, history, rituals and symbolism are woven into each meal, to ensure eating occurs in a relaxed state. On a whole, the Japanese diet is in complete contrast to the typical Western diet with the Japanese who eat in the traditional manner, in particular the Okinawans having one of the highest life expectancies in Japan and likely the world

One can instantly recognise the vast differences in diet when comparing the food pyramids of the Western world and Japan. Comparing both food pyramids, it would be fair to say that the Japanese get similar amounts of macronutrients to Westerners, but more varied types due to them being obtained from a greater variety of natural food sources. Survey of the diets of 200 elderly Japanese woman revealed they consumed a variety of over 100 biologically different foods each week. By contrast, western diets average 30. Eating a variety of foods increases the different arrays of nutrients one receives.

The main Japanese carbohydrate staples are rice and noodles, made from a variety of grains. There is minimal processing of grains, unlike the Western diet where most grains are refined and processed leaving minimal nutrients. Vegetables play a very important role in the Japanese diet. The more popular include bamboo shoot, eggplant, various mushrooms, cabbage, kelp and seaweeds. In comparison, the consumption of fruits and vegetables in Western diets has been decreasing. Fruit is typically served at the end of the meal with plums, mandarins, lychees and pears being the more popular. With the Japanese diet being so high in plant foods and legumes in particular the soybean and adzuki, the diet is also high in dietary fibre.

The main source of protein is from soy products and fish with meat eaten sparingly. Japanese eat twice as much fish as meat, while Westerners in contrast eat on average 47 times more meat than fish. Japanese have a very low consumption of dairy foods. Unlike the Western food pyramid other legumes, nuts and seeds are not consumed regularly. Traditional Japanese soybean products include tofu (soybean curd), natto (fermented soybean), miso (soybean paste) and shoyu (soy sauce). It would be fair to say, that although red meat does not feature strongly in the Japanese diet (once a month) most Japanese would receive all the essential amino acids through the high consumption of fish and soy which are both complete proteins, however may be deficient in haemo-iron.

Due to their minimal red meat consumption, the Japanese diet is low in fat, especially saturated fat. The Japanese consume on average 26% of energy as fats, one of the lowest fat intakes in the world. Most fats are derived from polyunsaturated sources such as rapeseed oil and soybean oils. Ratios of polyunsaturated to saturated fats are 1.2:1. The ratio of polyunsaturated fats to the essential fatty acids Omega 3 and 6 is 4:1. One would attribute this high intake of EFA’s to the greater consumption on a daily basis of fish and seafood. Very little fat is added to cooking as most Japanese dishes involve dashi a stock and seasoning made from kelp and soy sauce. In contrast to this, the Western diet is very high in saturated fats, in particular trans-fatty acids and low in the essential fats. Most western diets have an essential fatty acid ratio closer to 1:20. In comparison to the West, most Japanese food is pickled, fermented, smoked or eaten raw. Where most foods in the Western diet are processed, full of sugar and subsequently low in fibre, fried, microwaved, frozen or all of the above!

The vastness in variety of wholefoods, means the Japanese obtain a number of different micronutrients that are not found in such high quantities in the Western diet.

Soybeans, which feature daily in the Japanese diet, are an excellent source of folate iron, zinc and calcium as well as omega-3 fatty acids. One serving of beans provides more than half of the USA current RDA for folate. It is common that Western females in their reproductive years are advised to supplement their diets with folate as not enough is derived from the diet to protect from neural-tube defects during pregnancy.

Japanese receive a number of minerals and trace elements from sea vegetables such as wakame, kombu, nori and arame which are all seaweeds eaten on a daily basis. Seaweed contains the mineral macronutrients sodium, calcium, magnesium, potassium, chlorine, sulfur and phosphorus; mineral micronutrients include iodine, iron, zinc, copper, selenium, molybdenum, fluoride, manganese, boron, nickel and cobalt. Seaweed is the richest source of iodine and is the highest plant source of calcium. The Japanese low intake of red meat and dairy products increases their need for iron and calcium. The micronutrient sodium is particularly high in the diets of Japanese. Shoyo (Japanese soy sauce) contains 16% salt and is a feature of most Japanese dishes.

There are a number of phytochemicals and antioxidants that are unique to the traditional Japanese diet and have been shown to protect the health and aid in the longevity experienced by most Japanese. As documented by Arai et al, the high intake of flavonoids in the Japanese diet was attributed to vegetables, fruits, green tea, potatoes, tofu and other pulses.

Soy foods are the richest dietary source of isoflavones, the primary being genistein and daidzein. Foods made from soybeans have varying amounts of these isoflavones depending on how they have been processed. For example, Shoyo contains virtually no isoflavones due to the processing involved. As stated by Jenkins et al, isoflavones have been implicated in cholesterol lowering and the improvement of vascular reactivity due to their antioxidant activity. Japan’s national beverage is Green tea, which is steamed as opposed to fermented like most Western teas. The fermentation process destroys many of the medicinal properties. Tea has shown to contain a group of anti-oxidants called catechins. Studies have shown the preventive effect of green tea consumption against atherosclerosis, coronary heart disease, stroke, inflammation and some cancers.

DIET AND DISEASE

The high sodium intake discussed in the previous section is a health negative for the Japanese with high sodium chloride intakes being associated with a number of conditions including hypertension, asthma, osteoporosis and stomach cancer which was the most common cancer in Japan between 1955 - 1994. The high intake of pickled food could also be another negative. These foods contain nitrosamines, which have been implicated in stomach, liver, and oesophageal cancers. In comparison to the Western world, breast cancer is rare in Japan. It has been suggested that a low fat intake and a high intake of soy, antioxidants and fibre, plus high food variety are attributed. The inhabitants of Japan’s island of Okinawa, who follow a strict traditional Japanese diet have low blood levels of free radicals, low risk of cardiovascular disease, low risk of hormone dependent cancers, strong bones, low prevalence of dementia, youthful sex hormones. They also have one of the longest life expectancies in the world. It is the complete opposite for the populations existing on a typical Western diet with heart disease, cancer of all sorts, diabetes, dementia and stroke the major causes of death.

BENEFITS AND DISADVANTAGES

The benefits and disadvantages of the traditional Japanese diet have been clearly highlighted in the sections Nutrient Intakes and Diet and Disease. However, it is worthy to note that on a whole the Japanese people are at a disadvantage due to the radical Westernization of Japan since the 1950’s. Since this time, the Japanese have forgone their traditional diet to some extent to feast on the foods of the Western world, namely overly processed foods full of bad fats and sugar. This has led to an increase in childhood obesity, as well as cancers of the lung, liver, large intestine and breasts. Cancers which were non-existant prior to this time and most prevalent in Western society.

CONCLUSION

The Japanese way of eating, that is more variety of foods in small amounts appears to contribute advantageously to health. The higher intake of fruits, vegetables and fish and lower intakes of red meat and dairy play a major part in the low levels of disease commonly found in Western cultures. Also protecting the health of Japanese is the high intake of phytochemicals and antioxidants, with levels of these nutrients far exceeding levels found in people following a Western diet.

References:

Arai Y, Watanabe S, Kimira M, Shimoi K, Mochizuki R, Kinae N, 2000, Dietary intakes of Flavonols, Flavones and Isoflavones by Japanese Women and the Inverse Correlation between Quercetin Intake and Plasma LDL Cholesterol Concentration, Human Nutrition and Metabolism, Published by American Society for Nutritional Sciences

Barnett, C 1998, The Japanese Diet Nutrition News Number 85, retrieved 18 August 2003 from www.members.tripod.com/~Doc_In_The_Kitchen/japan.html

Jefferay K 2003 Introduction to Nutrition: A workbook to accompany lectures in Nutrition 1A, Australian College of Natural Therapies

Jefferay K 2003 Nutrition: The Macronutrients and Water: A workbook to accompany lectures in Nutrition 1B, Australian College of Natural Therapies

Jefferay K 2003, Pg 68 Current issues in Nutrition: A workbook to accompany lectures in Nutrition 1C, Australian College of Natural Therapies

Jefferay K 2003, Pg 69 Current issues in Nutrition: A workbook to accompany lectures in Nutrition 1C, Australian College of Natural Therapies

Jenkins D JA, Kendall C, Jackson, CC, Connelly P W, Parker T, Faulkner D, Vidgen E, Cunnane S C, Leiter L A, Josse R G, 2002, ‘Effects of high and low isoflavone soy foods on blood lipids, oxidised LDL, homocystine, and blood pressure in hyperlipidemia men and women’ American Journal of Clinical Nutrition 76:365-72, American Society for Clinical Nutrition

Mahan L K, Escott-Stump S, 1996 Krause’s Food, Nutrition & Diet Therapy, 9th ed, WB Saunders Company

Messina M J, ‘Legumes and Soybeans: Overview of their nutritional profile and health effects’ American Journal of Clinical Nutrition, September 1999 Volume 70, No. 3 439S-450S Published by American Society for Clinical Nutrition

Mukhtar H, Ahmad N, 2000, Tea polyphenols: prevention of cancer and optimising health, American Journal of Clinical Nutrition, 2000 Volume 71, 1698S-1702S, Published by American Society for Clinical Nutrition

Sugano M, Irahara F, ‘Polyunsaturated fatty acids in the food chain in Japan’ American Journal of Clinical Nutrition, January 2000, Volume 71, No. 1:186-196 Published by American Society for Clinical Nutrition

Whitney, Cataldo, Rolfes, Understanding Normal and Clinical Nutrition, 6th ed, 2002, Wandsworth

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