VITAMINS

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Many investigators have measured folate content in various foods using different methods over the past 50 years. These methods include the detection using microbiological assay, fluorometric or spectrophotometric methods in combination with various column chromatogaphies including HPLC. However, it has been known that the information in food folate tables is notoriously inaccurate. Recently, several groups of investigators have demonstrated that trienzyme treatment is essential to obtain the maximum possible value of folate in foods. Trienzyme treatment includes α-amylase and protease treatments for the extraction of food folate trapped or bound to protein or carbohydrate matrices, in addition to traditional folate conjugase treatment for the hydrolysis of polyglutamyl folates in foods. It is becoming clear that the conditions of pH and the duration of incubation for α-amylase and protease treatments vary significantly among individual food items. It is labor intensive and time consuming to identify the best conditions and perform trienzyme treatment in each food; therefore, it is a monumental task to make reliable and accurate food folate tables. However, it is important to establish dependable food folate tables in order to accurately estimate dietary intake of folate and to recommend adequate dietary folate intake in general populations, since the importance of folate nutriture for the maintenance of health as well as the prevention of certain diseases has become evident in recent years.

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In this study, changes in intake of fat, polyunsaturated fatty acid (PUFA), vitamin E (E) and E/ PUFA ratio (E/PUFA) were investigated on the basis of the data from the nutritional survey of Osaka citizens during the past 50 years. The total fat intake in Osaka citizens, which was less than 10% of total energy intake in 1946, increased by 5.5 fold during the past about 50 years. The increase in saturated fatty acids, mono-unsaturated fatty acids and PUFA were 6.3, 9,1 and 3.7 fold, respectively. The n-6/n-3 ratio was almost 4:1 throughout the period. E intake of 4.3mg/day in 1946 gradually increased during the next 30 years and reached the maximum of 8.7mg at 1975, which was maintained in the almost constant level for subsequent 20 years. However, the E/PUFA which is able to evaluate the E nutritional status, decreased from 1.07 in 1946 to 0.55 after 1994. If PUFA would be considered on the basis of its peroxidizability, E/PUFA-L fell less than 0.4 after 1965, the value of which continued to do till 1994. This finding should be taken into account on the evaluation of E requirement, although the total E intake recently increases to the recommended dose of 8mg as emphasized by the Japan Nutritional Requirement Council.

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