Although nutritional standards for Japanese were published by national organizations until the 1940s, the Recommended Dietary Allowances (RDAs) for Japanese was officially established in 1969 by the Ministry of Health and Welfare (presently Ministry of Health, Labour and Welfare). These RDAs were revised every five years until 2005, when they were established as Dietary Reference Intakes for Japanese (DRIs-J). The nutrients included in RDAs and DRIs-J were changed according to the health condition and eating habits of Japanese. The current version, DRIs-J 2010, comprises reference values for energy and 34 nutrients.
The Dietary Reference Intakes for Japanese (DRIs-J) 2010 was developed to provide reference values for the intake of energy and 34 nutrients for health maintenance and promotion and primary prevention of lifestyle-related diseases in healthy individuals and groups. The DRIs-J 2010, which follows the main concepts of the DRIs-J 2005, the prior version, provides the values for energy requirements as expressed by the estimated energy requirement (EER) and the values for nutrient intake as expressed by 5, the estimated average requirement (EAR), recommended dietary allowance (RDA), adequate intake (AI), tolerable upper intake level (UL), and tentative dietary goal for preventing lifestyle-related diseases (DG). On account of 3 factors—optimal intake varies among individuals, intake cannot be measured precisely, and the DRIs are aimed at maintaining health and preventing disease over the long term rather than addressing acute health effects in the short term—the DRIs were determined using the probability approach to provide the appropriate values for habitual rather than short-term intake. Each value of the DRIs used in the DRI-J 2010 is provided for 13 age groups (the values for energy and protein are provided for 14 groups), with separate values provided for women who are pregnant or lactating and for men and women. The EER is provided for 3 physical activity levels and the EAR, RDA, AI, and UL for 19, 18, 10, and 16 nutrients, respectively. The basic concepts behind the DRIs-J 2010 are almost same as those behind the DRIs of the United States and Canada with the unique exception that the DRIs-J 2010 also includes the DGs, dietary goals that were independently determined after consideration of the average body size, disease prevalence, and dietary habits of the Japanese population and the cumulative evidence regarding Japanese and East Asian populations. The DRIs-J 2010 has been used in practice since 2010 and is expected to be used until 2014. This review briefly describes the basic theories in its development.
The Dietary Reference Intakes for Japanese (DRIs-J) 2010 is not merely as scientific report describing the intake of energy and nutrients necessary for prevention of deficiency/insufficiency and excess but also a source of practical guidelines in planning for dietary improvement in general and in food services by dietitians and other health professionals. This review briefly describes the basic concepts in the application of the DRIs-J 2010. It consists of two sections considering the purposes of use in the Dietary Reference Intakes (DRIs) in Japan: (1) the basic concepts in their application and related issues and (2) the methods of their application. The latter is further divided into 3 sections each describing a goal in the application of the DRIs: (1) improvement of diet for an individual, (2) improvement of diet for a group, and (3) management of food services. A major challenge in the application of the DRIs is that compared to research into determination of the intake of energy and nutrients for development of the DRIs, research into application of the DRIs has been extremely scarce in Japan. Due to lack of evidence, current application of the DRIs is conceptual rather than scientific and practical. Highly scientific research into application of the DRIs is thus urgently needed.
For energy of Dietary Reference Intakes for Japanese (DRIs-J), the concept of Estimated Energy Requirement (EER) is applied. The EER has been established as an index for individuals and groups. The definition of EER for individuals is “habitual energy intake in a day which is predicted to have the highest probability that energy balance (energy in-take−energy expenditure, in adults) becomes zero in an individual of a given age, gender, height, body weight, and level of physical activity in good health.” In contrast, the definition of EER for a group is “habitual energy intake in a day which is predicted to have the highest probability that energy balance (energy intake−energy expenditure, in adults) becomes zero in a group.” The EER is calculated as follows: EER (kcal/d)=basal metabolic rate (BMR) (kcal/d)×physical activity level (PAL). Representative values for BMR per kg body weight are determined based on a number of reports for Japanese. This is called the reference value of BMR (reference BMR). Total energy expenditure measured by the doubly labeled water (DLW) method is utilized to determine PAL for each sex and age group. For adults, physical activity levels are determined based on data for Japanese adults. For children, energy deposition is added to the total energy expenditure. For pregnant and lactating women, additional values compared to EER before pregnancy for each stage of pregnancy and during lactation are calculated. Excess post-exercise oxygen consumption is not added to calculate EER in addition to energy expenditure during physical activity.
Proteins form the most important structural component of cells that constitute the various types of tissue, such as muscle, skin, and bone. Proteins also function as enzymes and hormones to regulate various metabolic processes in the body. The estimated average requirement (EAR) of protein for both men and women who habitually consume mixed protein was evaluated as 0.72 g/kg body weight/d by nitrogen balance studies as the value to maintain nitrogen equilibrium with high quality protein, revised with digestibility of mixed protein in habitual food intake. The recommended intake of protein for infants is normally based on the adequate intake (AI) standard, which reflects the observed mean protein intake of infants fed principally with breast milk for up to 6 mo of age. The EAR of children aged 1-17 y was estimated by the factorial method, which adds the amount required for protein storage because of growth and protein requirement for maintenance. The EAR of protein in the elderly was calculated by meta-analysis, employing 144 data sets obtained from 5 published reports, with 60 subjects, and was found to be 0.85 g of habitual mixed protein/kg body weight/d. The tolerable upper intake level (UL) of protein must be established based on the health risk caused by excessive protein intake. However, no clear evidence to establish this value is available at present, and therefore, the UL of protein cannot be determined.
In the Dietary Reference Intakes (DRIs) for fat, adequate intake (AI) and tentative dietary goal for preventing lifestyle-related disease (DGs) were used. AIs were set for n-6 and n-3 polyunsaturated fatty acids, which are essential fatty acids because they are not produced by the human body and their deficiency leads to dermatitis. DGs have been set for total fat, saturated fat, n-6 fatty acids, n-3 fatty acids, and cholesterol, whose consumption levels affect risk of lifestyle-related disease, including obesity, diabetes mellitus, cardiovascular disease, and stroke. As AI for n-6 and n-3 polyunsaturated fatty acids, the 50th percentile of n-6 and n-3 fatty acid intake was set. In the Japanese population, 98% of dietary n-6 fatty acids come from linoleic acid; therefore the amount of n-6 fatty acid intake is considered to be that of linoleic acid. Both α-linolenic (60% of total n-3 fatty acids) acid and fish oils are considered essential fatty acids because it has been difficult to conclude that only α-linolenic acid is essential for humans. The prevention of diabetes mellitus and stroke was emphasized. For example, an increase in saturated fatty acids intake leads to increased incidences in obesity, diabetes, and myocardial infarction, whereas a decrease of saturated fatty acids intake is associated with increased incidence in brain hemorrhage. Therefore, DG of saturated fatty acids in those more than 18 y of age was set between 4.5 and 7% energy.
The Dietary Reference Intakes (DRIs) of carbohydrates and dietary fiber were determined for Japanese. The estimated average requirement (EAR) and recommended dietary allowance (RDA) for carbohydrates were not determined because of insufficient data. The tentative dietary goal for preventing lifestyle-related diseases (DG) for children aged 1 y and above was determined for carbohydrates (% energy). In addition, the DG for adults aged 18 y and above was determined for dietary fiber. Dietary fiber intake is associated with myocardial infarction; therefore, the DG was determined on the basis of the results of a meta-analysis and the median dietary fiber intake of Japanese. The DG for alcohol was not determined because of insufficient data.
We have determined the Dietary Reference Intakes for fat-soluble vitamins (vitamin A, vitamin D, vitamin E, and vitamin K) for the Japanese. Regarding vitamin A, the estimated average requirement (EAR) and the recommended dietary allowance (RDA) were defined for those aged 1 y old and over. For vitamin D, vitamin E, and vitamin K, the EAR or RDA was not adopted, because of the insufficient data available. Thus, the adequate intake (AI) was determined for those vitamins based on the food surveillance data and biomarkers for each vitamin. The AI for vitamin D was decided as the median intake of vitamin D in the population with a circulating 25-hydroxy vitamin D level which was high enough for bone health. The basis for the AI for vitamin E was the median intake of α-tocopherol in the healthy population considering the lack of unfavorable health consequences attributable to its deficiency. The AI for vitamin K was determined as the vitamin K intake, required to avoid blood coagulation abnormalities. The tolerable upper intake level (UL) was determined for vitamin A, vitamin D and vitamin E, but not for vitamin K, since no adverse effects have been reported even with its high dosage.
A potential approach for determining the estimated average requirement (EAR) is based on the observation that a water-soluble vitamin or its catabolite(s) can be detected in urine. In this approach, the urinary excretion of a water-soluble vitamin or its catabolite(s) increase when the intake exceeds the requirement. This approach is applied to vitamin B1, vitamin B2 and niacin. A second approach is to determine the blood concentration. In this case, the requirement is indicated by a value rather than a threshold level. The second approach is applied to vitamin B6, vitamin B12, folate, and vitamin C. The recommended dietary allowance (RDA) was calculated by multiplying the EAR by 1.2. For pantothenic acid and biotin, there were insufficient data for determining the EAR. Thus, adequate intakes were set based on food surveillance data.
Dietary Reference Intakes of five macrominerals (sodium, potassium, calcium, magnesium and phosphate) were determined for Japanese. The estimated average requirement (EAR) and the recommended dietary allowance (RDA) for adults ages 18 y and older were determined in calcium and magnesium. In sodium, the EAR was determined. The RDA was not determined because the values were much lower than normal intake levels. Furthermore the dietary goal for preventing lifestyle-related diseases (DG) was determined based on preventing hypertension. In potassium, the value that is considered appropriate to maintain in vivo potassium balance was used as the adequate intake, the DG was established from a standpoint of prevention of hypertension. In calcium, the EAR and RDA were determined by the factorial method. In phosphate, the AI was determined based on the intake level of the National Health and Nutrition Surveys. The tolerable upper intake level (UL) for adults was determined in calcium, phosphate and magnesium, but the UL of magnesium was applied from a source other than ordinary food.
The Dietary Reference Intakes (DRIs) of 8 microminerals (iron, zinc, copper, manganese, iodine, selenium, chromium and molybdenum) were determined for Japanese. The estimated average requirement (EAR) and the recommended dietary allowance (RDA) for adults ages 18 y and older were determined in seven microminerals other than for manganese. Due to lack of data with which to set the EAR for manganese, determination of the adequate intake (AI) of manganese was based on the average manganese intake of the Japanese population. Data with which to determine the EARs were obtained using the following methods: iron and zinc, use of a factorial modeling method; copper and selenium, determination of the relationship between biomarkers and intake; iodine, determination of thyroid iodine accumulation and turnover; and chromium and molybdenum, performance of a balance test. The EARs and RDAs of iron, zinc, copper, iodine and selenium for children and adolescents aged 1 to 17 y were also determined. Based on the average micromineral concentration in the milk of Japanese women and the average intake of breast milk in Japanese infants, the AI for infants was determined for 8 microminerals. The tolerable upper intake level (ULs) of adults were determined for all microminerals except chromium, for which there are insufficient data. The ULs for iron, iodine and selenium for children and adolescents were also determined.
The Dietary Reference Intakes for Japanese 2010 (DRIs-J 2010) included a new chapter for lifestage. In this chapter, important characteristics of the nutritional status and the special considerations in applying for DRIs in each lifestage—infants and children, pregnant and lactating women, and the elderly—were described. In infants, the references of nutrient requirement are mostly presented by adequate intake (AI) because of the impossibility of human experiments to determine the estimated average requirement (EAR). The quality and quantity of breast milk is assumed to be nutritionally desirable for every infant. Therefore, AI was determined on the basis value obtained by nutritional concentration and average amount of breast milk consumed by healthy infants. In addition, the anthropometric references for 4 periods based on the 50th percentiles in growth curves were newly demonstrated. The nutrient requirement increased in the pregnant and lactating stage. Increments were estimated based on the fetal growth during whole pregnancy period in pregnant women and on the daily milk production of 780 mL/d in lactating women. In the elderly stage, the scarcity of nutritional studies regarding the Japanese elderly makes it difficult to determine the appropriate DRI values for the elderly. Furthermore, the changes in nutritional status and physical function with aging have been influenced by not only the chronological age but also various other factors, which complicates the establishment of DRIs for the elderly. In light of these facts, the promotion of further and more comprehensive studies of the elderly is desirable.