BACKGROUND/OBJECTIVES: The Dietary Reference Intakes for Koreans (KDRIs) were revised in 2020. Due to the rapidly aging Korean population, special consideration was given to reclassify the KDRI age group categories of older adults. This article examines the evidence for modifying the current KDRI age group ranges of older adults (65-74 and ≥ 75 yrs). SUBJECTS/METHODS: We first reviewed the domestic and international data on the elderly, following which we received expert opinions on age classification from the KDRI Advisory Committee. Finally, the 6th and 7th (2013-2017) Korea National Health and Nutrition Examination Survey (KNHANES) data were used to analyze the nutritional intake statuses by considering the age of older adults. RESULTS: According to the review results of domestic and international data and the inputs received from the expert advisory committee, the minimum age considered for the elderly was maintained at 65 yrs. However, the KNHANES data was analyzed to review whether there was a need to subdivide the later periods. Examining the differences in nutrient intakes by age group through the interaction effect term of the piecewise linear regression model revealed the interaction effect was maximum in the groups divided by 65 yrs (50-64 and 65-80), as compared to the groups divided by 70 yrs (50-69 and 70-80) and 75 yrs (50-74 and 75-80). The mean adequacy ratio was calculated per 1 yr of age, and a 3-yr (age) moving average analysis was performed to examine the change in the trends of overall nutrient intake. However, it was challenging to secure a scientific basis for subdivision into age groups in older adults from the results obtained. CONCLUSIONS: This study could not find any scientific evidence for modifying the KDRI age groups for older adults.

Research articles were reviewed to validate the estimated energy requirements (EERs) equations developed by the Institute of Medicine of the National Academies (IOM). These equations are based on total energy expenditure (TEE) measured by the doubly labeled water (DLW) method. We subsequently aimed to provide the basis for the suitability to apply the IOM equations as EER equations for Koreans, and develop relevant equations for EER in the Dietary Reference Intake for Koreans (KDRI). Additionally, besides the EER(IOM) equations, other equations were examined for EER estimation. Research papers demonstrating the validation of the EER(IOM) equations based on TEE(DLW) were searched through PubMed (up to September 2019). Of the 637 potentially relevant articles identified, duplicates and unsuitable titles and abstracts were excluded. Furthermore, papers with irrelevant subject and inappropriate study design were also excluded. Finally, 11 papers were included in the review. Among the reviewed papers, 8 papers validated the application of the EER(IOM) equations for EER based on TEE(DLW). These included 3 studies for children (USA 1, Korea 2), 1 for adolescents (Portugal), 2 for adults (Korean), and 2 for the elderly (Korea, USA). EER(IOM) equations were found to be generally acceptable for determining EER by using the DLW method, except for Korean boys at 9-11 yrs (overestimated) and female athletes at 19-24 yrs (underestimated). Additionally, 5 papers include the validation of other EER equations, beside EER(IOM) for EER based on TEE(DLW). In Japanese dietary reference intake and recommended dietary allowance, EER equations are acceptable for determining EER based on TEE(DLW). The EER(IOM) equations is generally acceptable for determining EER using the DLW method in Koreans as well as several populations, although certain defined groups were found to be unfit for the estimation. Additionally, the concept of healthy body mass index of Koreans and physical activity levels need to be considered, thereby providing the basis for developing relevant equations of EER in KDRI.

BACKGROUND/OBJECTIVES: The long-term health impacts of dietary sugar have begun to be reported. The committee on the 2020 Dietary Reference Intakes for Koreans for sugar intended to update the scientific evidence on the association of added sugar intake with health outcomes, including mortality. This study evaluated the evidence on the association of dietary sugar with the all-cause and cardiovascular disease mortality from cohort studies. SUBJECTS/METHODS: The PubMed and ScienceDirect databases were searched until July 2021. The search terms were based on multiple combinations of keywords, such as added sugar, beverage, and mortality, included in the title or abstract. Two authors independently assessed the eligibility criteria of study selection and extracted the information from each selected article for this systematic review. RESULTS: The literature search identified 276 articles. Seventeen cohort studies met the inclusion criteria and were included in this systematic review. This study extracted information on the cohort and participants, dietary assessment methods, exposure and its comparison groups, health outcomes, and risk measures. Five articles reported added sugar intake, and 15 articles reported the food sources of the added sugar in the association with mortality. Increased mortality was observed in higher added sugar intake and a lower intake of less than 5% of energy, while higher discrepancies between gender, age groups, and countries were noted. In addition, nutritious sugary foods and beverages did not increase mortality. CONCLUSIONS: A 'U' or 'J' shaped relationship between the added sugar intake and mortality was estimated. The observed discrepancy indicated the need for more evidence to establish the dose-response relationship for Koreans.

The Korea National Health and Nutrition Examination Survey of 2013 to 2017 reported that the average protein consumption of the Korean population is above the current recommended nutrient intake of protein proposed by the Dietary Reference Intakes for Koreans. Some health professionals and the media often advise consuming diets high in protein for promoting metabolic regulation, weight control, and muscle synthesis. However, due to lack of scientific evidence, the validity and safety of high protein consumption are yet to be fully ascertained. The present review assesses recent evidence published in 2014-2020 from human studies, focusing on adequate protein intake and protein sources for the prevention of chronic diseases, particularly metabolic disorders and sarcopenia.

This paper examines the process and evidence used to create the Dietary Reference Intake (DRI) of alpha-linolenic acid (ALA) and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) for Koreans. ALA (18:3n3) is an essential fatty acid, and EPA and DHA are known to have beneficial effects on cardiovascular disease risk and reduction of triglyceride levels. Various international organizations have suggested dietary recommendations for n-3 polyunsaturated fatty acids (PUFAs), including ALA, EPA, and DHA. A DRI for Koreans was established for the first time in 2020, specifically for the adequate intake (AI) of ALA and EPA + DHA. This recommendation was based on the average intake of ALA and EPA + DHA from the Korea National Health and Nutrition Examination Survey 2013-2017. For Korean infants, the AI of ALA and DHA was based on the fatty acid composition of maternal milk. Estimated average requirement and a tolerable upper intake level have not been set for n-3 PUFA due to insufficient evidence. In addition, the intake level of n-3 PUFA for prevention of chronic disease has also not been determined. Future studies and randomized controlled trials are required to establish the UL and to define the level for disease prevention.

BACKGROUND/OBJECTIVES: Vitamin D is produced in the skin during sun exposure and is also ingested from foods. The role of vitamin D needs to be considered in the prevention and management of various diseases. Moreover, since the majority of Koreans spend their days indoors, becoming susceptible to the risk of vitamin D deficiency. The current study aims to prepare a basis for determining dietary reference intake of vitamin D in Korea, by reviewing the evidence against various diseases and risks. MATERIALS/METHODS: Literature published in Korea and other countries between 2014 and 2018 was prioritized based on their study design and other criteria, and evaluated using the RoB 2.0 assessment form and United States Department of Agriculture Nutrition Evidence Library Conclusion Statement Evaluation Criteria. RESULTS: Of the 1,709 studies, 128 studies were included in the final systematic analysis after screening. To set the dietary reference intakes of vitamin D based on the selected articles, blood 25(OH)D levels and indicators of bone health were used collectively. Blood vitamin D levels and ultraviolet (UV) exposure time derived from the Korean National Health and Nutrition Examination Survey were analyzed to establish the dietary reference intakes of vitamin D for each stage of the life cycle. The adequate intake levels of vitamin D, according to age and gender, were determined to be in the range of 5-15 ㎍/day, and the tolerable upper intake level was established at 25-100 ㎍/day. CONCLUSIONS: The most important variable for vitamin D nutrition is lifestyle. A balanced diet comprising foods with high contents of vitamin D is important, as is vitamin D synthesis after UV exposure. The adequate intake level of vitamin D mentioned in the 2015 Dietary Reference Intakes for Korean (KDRI) remained unchanged in the 2020 KDRI for the management of vitamin D nutrition in Koreans.

Sodium is a physiologically essential nutrient, but excessive intake is linked to the increased risk of various chronic diseases, particularly cardiovascular. It is, therefore, necessary to accomplish an evidence-based approach and establish the Korean Dietary Reference Intakes (KDRIs) index, to identify both the nutritional adequacy and health effects of sodium. This review presents the rationale for and the process of revising the KDRIs for sodium and, more importantly, establishing the sodium Chronic Disease Risk Reduction Intake (CDRR) level, which is a new specific set of values for chronic disease risk reduction. To establish the 2020 KDRIs for dietary sodium, the committee conducted a systematic literature review of the intake-response relationships between the selected indicators for sodium levels and human chronic diseases. In this review, 43 studies published from January 2014 to December 2018, using databases of PubMed and Web of Science, were finally included for evaluating the risk of bias and strength of evidence (SoE). We determined that SoE of the relationship between dietary sodium and cardiovascular diseases, cerebrovascular disease, and hypertension, was moderate to strong. However, due to insufficient scientific evidence, we were unable to establish the estimated average requirement and the recommended nutrient intake for dietary sodium. Therefore, the adequate intake of sodium for adults was established to be 1,500 mg/day, whereas the CDRR for dietary sodium was established at 2,300 mg/day for adults. Intake goal for dietary sodium established in the 2015 KDRIs instead of the tolerable upper intake level was not presented in the 2020 KDRIs. For the next revision of the KDRIs, there is a requirement to pursue further studies on nutritional adequacy and toxicity of dietary sodium, and their associations with chronic disease endpoint in the Korean population.

An accurate assessment of the recommended calcium (Ca) intake may contribute to reducing the risk of fractures and chronic diseases, ultimately improving quality of life. This review was performed to summarize key findings of Ca studies, investigate the effect of Ca intake on health outcomes, and determine the adequacy of evidence to revise the 2015 Dietary Reference Intakes for Koreans (KDRIs) for Ca in 2020. Databases were searched for intervention studies that assessed health outcomes by providing Ca in diets or as supplements. The framework of the systematic review comprised conducting literature searches, data extraction, quality assessment of the literature, and summarizing key findings relevant to set the Estimated Average Requirement (EAR) and Tolerable Upper Intake Level (UL) for Ca for the 2020 KDRI. The final search was performed in June 2019. A total of 13,309 studies were identified through databases and manual search. Sixtyfive studies were included in the final quality assessment and were summarized according to health indicators. As bone health was used as an indicator of the EAR for Ca, literature reports on bone health were further categorized by the life-cycle stage of the participants. This systematic review did not find new evidence that could be applied to the general Korean adult population, including postmenopausal women, for defining a new EAR for Ca in the 2020 KDRIs. Evidence in most of the reviewed literature was considered weak; however, some evidence was found that could improve the criteria on how the EAR for Ca was determined in children and adolescents. A review of the literature for the 2020 KDRIs for Ca did not find strong evidence in order to change the recommended values of the 2015 KDRIs. More clinical interventions are required among Koreans to strengthen the body of evidence to warrant the revision of the KDRIs.

In the current years, it has now become necessary to establish standards for micronutrient intake based on scientific evidence. This review discusses issues related to the development of the 2020 Dietary Reference Intakes for Koreans (KDRI) for magnesium (Mg), zinc (Zn), and copper (Cu), and future research directions. Following issues were encountered when establishing the KDRI for these minerals. First, characteristics of Korean subjects need to be applied to estimate nutrient requirements. When calculating the estimated average requirement (EAR), the KDRI used the results of balance studies for Mg absorption and factorial analysis for Zn, which is defined as the minimum amount to offset endogenous losses for Zn and Mg. For Cu, a combination of indicators, such as depletion/repletion studies, were applied, wherein all reference values were based on data obtained from other countries. Second, there was a limitation in that it was difficult to determine whether reference values of Mg, Zn, and Cu intakes in the 2020 KDRI were achievable. This might be due to the lack of representative previous studies on intakes of these nutrients, and an insufficient database for Mg, Zn, and Cu contents in foods. This lack of database for mineral content in food poses a problem when evaluating the appropriateness of intake. Third, data was insufficient to assess the adequacy of Mg, Zn, and Cu intakes from supplements when calculating reference values, considering the rise in both demand and intake of mineral supplements. Mg is more likely to be consumed as a multi-nutrient supplement in combination with other minerals than as a single supplement. Moreover, Zn-Cu interactions in the body need to be considered when determining the reference intake values of Zn and Cu. It is recommended to discuss these issues present in the 2020 KDRI development for Mg, Zn, and Cu intakes in a systematic way, and to find relevant solutions.

Choline is a water-soluble organic compound that is important for the normal functioning of the body. It is an essential dietary component as de novo synthesis by the human body is insufficient. Since the United States set the Adequate Intakes (AIs) for total choline as dietary reference values in 1998, Australia, China, and the European Union have also established the choline AIs. Although choline is clearly essential to life, the 2020 Dietary Reference Intakes for Koreans (KDRIs) has not established the values because very few studies have been done on choline intake in Koreans. Since choline intake levels differ by race and country, human studies on Koreans are essential to set KDRIs. Therefore, the present study was undertaken to provide basic data for developing choline KDRIs in the future by analyzing data on choline intake in Koreans to date and reference values of choline intake and dietary choline intake status by country and race.

BACKGROUND/OBJECTIVES: Accumulating evidence has shown the beneficial effects of isoflavone on health. There is limited information on the usual isoflavone intake for Koreans. This study examined the usual intake of total isoflavone and its major food sources in Koreans according to age and gender. SUBJECTS/METHODS: The dietary intake data of 21,271 participants aged 1 yrs and older from the Korea National Health and Nutrition Examination Survey (KNHANES) VII 2016-2018 were analyzed. The average isoflavone intake was estimated based on the 24-h dietary recall data in KNHANES and the isoflavone database from the Korea Rural Development Administration (RDA) and literatures. The usual isoflavone intake was estimated by applying the ratio of within- and between-participant variance estimated from the 2009 KNHANES data to the 7th KNHANES (2016-2018) data. The variance of the isoflavone intake was calculated using MIXTRAN macro with intake data for two days in the 2009 KNHANES. Complex sample analysis with stratified variables and integrated weights was conducted. RESULTS: The mean total isoflavone intake in the Korean population aged 1 yrs and older (n = 21,271) was 139.27 mg/d, which was higher than the usual intake of 47.44mg/d. Legumes were a major contributing food group (91%), with arrowroot being a major individual contributor to the isoflavone intake (67.2%), followed by 21.3% of soybean, 5.4% of bean sprouts, and 2.1% of tofu. The usual isoflavone intake was highest in the participants aged 50 to 64 yrs old and increased with age until 50 to 64 yrs and then decreased with further increases in age. The usual isoflavone intake of participants aged 65 yrs and older was higher for men than for women, showing gender differences. CONCLUSIONS: The usual dietary intake of isoflavone varied according to age and gender in the Korean population. This study showed that the usual isoflavone intake was lower than the average isoflavone intake. The difference between percentiles of the usual isoflavone intake was similarly smaller than the average intake. An estimation of average intake can be hindered by the occasional consumption of foods high in isoflavones, suggesting that the usual intake estimation method can be more appropriate. Further research will be needed to establish isoflavone dietary guidelines regarding the effects of isoflavone intake on health outcomes.

BACKGROUND/OBJECTIVES: Complementary and alternative medicines can be used to alleviate climacteric symptoms that significantly affect the quality of life of postmenopausal women. Isoflavones are the most common plant-based therapies for postmenopausal changes, but the results of previous studies have been controversial. MATERIALS/METHODS: To investigate whether isoflavones would affect menopausal symptoms as well as ovarian hormones, we performed a systematic review and meta-analysis. The PubMed and EMBASE databases were used to perform the systematic search. Included studies were limited to randomized controlled trials (RCTs) assessing the impact of isoflavone supplementation on menopausal symptoms. RESULTS: Eleven studies were included for the final quantitative assessment. Isoflavone intervention was varied between 49.3 and 135 mg of isoflavones per day for 12 wk-2 yrs. The meta-analysis showed that supplementation of isoflavones significantly increased the estradiol levels (standardized mean difference [SMD] = 0.615, P = 0.035) and Kupperman index (SMD = 3.121, P = 0.003) but had no significant effect on hot flashes, follicle-stimulating hormone, and luteinizing hormone. However, both estradiol and the Kupperman index showed significant heterogeneity among studies (I² = 94.7%, P < 0.001 and I² = 98.1%, P < 0.001, respectively). CONCLUSIONS: Although the results showed a significant SMD in estradiol and the Kupperman index, the results should be interpreted with caution due to the high heterogeneity. Further validation with a larger RCT will be necessary. Overall, isoflavone supplementation has distinct effects on the climacteric symptoms and hormonal changes in postmenopausal women.