Blood carotenoid concentration measurement is considered the gold standard for fruit and vegetable (F&V) intake estimation; however, this method is invasive and expensive. Recently, skin carotenoid status (SCS) measured by optical sensors has been evaluated as a promising parameter for F&V intake estimation. In this cross-sectional study, we aimed to validate the utility of resonance Raman spectroscopy (RRS)-assessed SCS as a biomarker of F&V intake in Korean adults. We used data from 108 participants aged 20–69 years who completed SCS measurements, blood collection and 3-d dietary recordings. Serum carotenoid concentrations were quantified using HPLC, and dietary carotenoid and F&V intakes were estimated via 3-d dietary records using a carotenoid database for common Korean foods. The correlations of the SCS with serum carotenoid concentrations, dietary carotenoid intake and F&V intake were examined to assess SCS validity. SCS was positively correlated with total serum carotenoid concentration (r = 0·52, 95 % CI = 0·36, 0·64, P < 0·001), serum β-carotene concentration (r = 0·60, 95 % CI = 0·47, 0·71, P < 0·001), total carotenoid intake (r = 0·20, 95 % CI = 0·01, 0·37, P = 0·04), β-carotene intake (r = 0·30, 95 % CI = 0·11, 0·46, P = 0·002) and F&V intake (r = 0·40, 95 % CI = 0·23, 0·55, P < 0·001). These results suggest that SCS can be a valid biomarker of F&V intake in Korean adults.

The present study investigated the association between protein intake and lean mass according to obesity status over a 12-year period. Data on 4412 participants aged 40–69 years were obtained from the Korean Genome and Epidemiology Study. The usual dietary protein intake of these participants was assessed at baseline using a semi-quantitative FFQ. Body composition was measured using bioelectrical impedance analysis at baseline and after a 12-year follow-up. Linear mixed-effects models were used to examine the associations between lean mass after a 12-year follow-up and protein intake at baseline. After adjusting for covariates and lean mass at baseline, comparisons between the highest and lowest tertiles revealed that dietary protein intake was positively associated with lean mass in both men (β = 0·79, P = 0·001) and women (β = 0·28, P = 0·082) after the 12-year period; however, those differences were attenuated after additional adjustment for fat mass at baseline and were stronger in the normal-weight group (men, β = 0·85, P = 0·002; women, β = 0·97, P < 0·001) but were not detected in the obese group. In the obese group, age (men, β = 4·08, P < 0·001; women, β = 2·61, P < 0·001) and regular physical activity (men, β = 0·88, P = 0·054; women, β = 0·76, P < 0·001) were significantly associated with lean mass after 12 years of follow-up. The results of the present study showed that protein intake may contribute to the prevention of ageing-related lean mass loss; however, the impact of this intake may vary depending on obesity status. Therefore, the maintenance of a healthy body weight during ageing through enhanced protein intake is likely to confer health benefits.

Over a few decades, Korean diet has changed from traditional diet, mainly composed of rice and vegetables, to Westernised diet rich, in meat and milk, along with the economic development and globalisation. Increasing prevalence of diet-related chronic diseases such as cancer and metabolic syndrome (MetS) is becoming a heavy burden to society and requires further attention. In this review, the association of meat and milk consumption with cancer and MetS among Koreans was discussed. Previous meta-analyses showed that meat intake was positively associated with increased risk of cancers, especially colon, as well as obesity and type 2 diabetes mellitus, and that the intake of milk and dairy products was negatively associated with colorectal cancer, obesity, and type 2 diabetes mellitus, based on studies conducted mostly in Western countries. In Korea and other Asian countries, the association of meat and milk intake with cancers were inconclusive and varied by types of cancers. Conversely, milk intake was negatively associated with MetS risk as reported in Western countries. The difference in results between Korea and Western countries might come from the differences in dietary patterns and study designs. Most Koreans still maintain traditional dietary pattern, although rapid change towards Westernised diet is underway among the younger age group. Randomised clinical trials or prospective cohort studies with consideration of combined effects of various dietary factors in Korea and other Asian countries are needed to elucidate the impact of meat and milk or related dietary patterns in their diet.

Epidemiological studies have suggested that flavonoids exhibit preventive effects on degenerative diseases. However, lack of sufficient data on flavonoid intake has limited evaluating the proposed effects in populations. Therefore, we aimed to estimate the total and individual flavonoid intakes among Korean adults and determine the major dietary sources of these flavonoids. We constructed a flavonoid database of common Korean foods, based on the food list reported in the 24-h recall of the Korea National Health and Nutrition Examination Survey (KNHANES) 2007–2012, using data from the Korea Functional Food Composition Table, US Department of Agriculture flavonoid database, Phenol-Explorer database and other analytical studies. This database, which covers 49 % of food items and 76 % of food intake, was linked with the 24-h recall data of 33 581 subjects aged ≥19 years in the KNHANES 2007–2012. The mean daily intake of total flavonoids in Korean adults was 318·0 mg/d, from proanthocyanidins (22·3 %), flavonols (20·3 %), isoflavones (18·1 %), flavan-3-ols (16·2 %), anthocyanidins (11·6 %), flavanones (11·3 %) and flavones (0·3 %). The major contributing food groups to the flavonoid intake were fruits (54·4 %), vegetables (20·5 %), legumes and legume products (16·2 %) and beverages and alcohols (3·1 %), and the major contributing food items were apples (21·9 %), mandarins (12·5 %), tofu (11·5 %), onions (9·6 %) and grapes (9·0 %). In the regression analysis, the consumption of legumes and legume products, vegetables and fruits predicted total flavonoid intake the most. The findings of this study could facilitate further investigation on the health benefits of flavonoids and provide the basic information for establishing recommended flavonoid intakes for Koreans.

Cancer is a leading cause of death, and the dietary pattern in Korea is changing rapidly from a traditional Korean diet to a Westernised diet. In the present study, we investigated the effects of dietary factors on cancer risk with a prospective cohort study. Among 26 815 individuals who participated in cancer screening examinations from September 2004 to December 2008, 8024 subjects who completed a self-administered questionnaire concerning demographic and lifestyle factors, and a 3 d food record were selected. As of September 2013, 387 cancer cases were identified from the National Cancer Registry System, and the remaining individuals were included in the control group. The hazard ratio (HR) of cancer for the subjects older than or equal to 50 years of age was higher (HR 1·80, 95 % CI 1·41, 2·31; P< 0·0001) than that for the other subjects. Red meat consumption, Na intake and obesity (BMI ≥ 25 kg/m2) were positively associated with overall cancer incidence in men (HR 1·41, 95 % CI 1·02, 1·94; P= 0·0382), gastric cancer (HR 2·34, 95 % CI 1·06, 5·19; P= 0·0365) and thyroid cancer (HR 1·56, 95 % CI 1·05, 2·31; P= 0·0270), respectively. Participants who had at least three dietary risk factors among the high intakes of red meat and Na, low intakes of vegetables and fruits, and obesity suggested by the World Cancer Research Fund/American Institute for Cancer Research at baseline tended to have a higher risk of cancer than the others (HR 1·26, 95 % CI 0·99, 1·60; P= 0·0653). In summary, high intakes of red meat and Na were significant risk factors of cancer among Koreans.

Sources of variation in nutrient intake have been examined for Western diets, but little is known about the sources of variation and their differences by age and sex among Koreans. We examined sources of variation in nutrient intake and calculated the number of days needed to estimate usual intake using 12 d of dietary records (DR). To this end, four 3 d DR including two weekdays and one weekend day were collected throughout four seasons of 1 year from 178 male and 236 female adults aged 20–65 years residing in Seoul, Korea. The sources of variation were estimated using the random-effects model, and the variation ratio (within-individual:between-individual) was calculated to determine a desirable number of days. Variations attributable to the day of the week, recording sequence and seasonality were generally small, although the degree of variation differed by sex and age (20–45 years and 46–65 years). The correlation coefficient between the true intake and the observed intake (r) increased with additional DR days, reaching 0·7 at 3–4 d and 0·8 at 6–7 d. However, the degree of increase became attenuated with additional days: r increased by 13·0–26·9 % from 2 to 4 d, by 6·5–16·4 % from 4 to 7 d and by 4·0–11·6 % from 7 to 12 d for energy and fifteen nutrients. In conclusion, the present study suggests that the day of the week, recording sequence and seasonality minimally contribute to the variation in nutrient intake. To measure Korean usual dietary intake using open-ended dietary instruments, 3–4 d may be needed to achieve modest precision (r>0·7) and 6–7 d for high precision (r>0·8).

The aim of the present study was to identify the association of dietary patterns with osteoporosis in Korean postmenopausal women from the Korean Health and Nutrition Examination Survey 2008–10. The present cross-sectional analysis included 3735 postmenopausal women who completed a health interview, nutrition survey and a health examination including bone mineral density (BMD) measurements. The general characteristics and dietary intakes of the participants were obtained using a standardised questionnaire and a 24 h recall method, respectively. The BMD of the femoral neck and lumbar spine was measured using dual-energy X-ray absorptiometry; osteoporosis was defined based on the WHO T-score criteria. Overall, we identified four dietary patterns using factor analysis as follows: ‘meat, alcohol and sugar’, ‘vegetables and soya sauce’, ‘white rice, kimchi and seaweed’ and ‘dairy and fruit’, which accounted for 30·9 % of the total variance in food intake (11·3, 7·7, 6·0 and 5·9 %, respectively). The subjects in the highest quintile of the ‘dairy and fruit’ pattern showed a decreased risk of osteoporosis of the lumbar spine (53 %) compared with those in the lowest quintile, after adjusting for covariates (OR 0·47, 95 % CI 0·35, 0·65, P for trend < 0·0001). In contrast, the ‘white rice, kimchi and seaweed’ dietary pattern was negatively associated with bone health (OR 1·40, 95 % CI 1·03, 1·90, P for trend = 0·0479). The present results suggest that an increased intake of dairy foods and fruits in the traditional Korean diet, based on white rice and vegetables, may decrease the risk of osteoporosis in Korean postmenopausal women.

We used a database approach in developing a dish-based, semi-quantitative FFQ for Korean diet and cancer research. Cancer-related dietary factors (CRDF) recognised in the scientific community and dietary intake data from the 2001 Korean National Health and Nutrition Examination Survey and the 2002 Korean National Nutrition Survey by Season were used. The list of dishes (n 993) was those reported to be consumed by individuals over 30 years of age during all four seasons. The resulting 112-dish list was selected using contribution analyses and variability analyses to detect between-person variation for CRDF and non-CRDF nutrients. Variations of each dish were grouped into one dish for the final list of 112 dishes, which were then linked to the nutrient database. The final 112 dish items consisted of nine Korean staple dishes, including rice and noodles, twenty-five soups and stews, fifty-four side dishes, nine beverages, nine fruit dishes and six alcoholic beverages. The percentage coverages of energy, protein, fat, carbohydrate and alcohol intake in the selected 112 dishes were 82·4, 76·4, 68·9, 86·0 and 99·8 %, respectively. Dietary exposure to cancer-related Korean dietary factors can be assessed by this new dish-based, semi-quantitative FFQ. This new instrument can calculate the intake of CRDF along with non-CRDF nutrient intake for cancer research.

Little is known about the bioavailability of isoflavones in children. Previous studies have shown that children excrete more isoflavone in urine compared with adults. Thus we examined the relationship between usual dietary isoflavone intake and the urinary excretion of isoflavonoids in Korean girls of pubertal age. Twelve girls each were selected from the lowest and the highest quartiles of isoflavone intake among 252 Korean girls aged 8–11 years. Age, BMI and sexual maturation stage were matched between the two groups. Dietary intakes for 3 d by diet record and overnight urine samples were collected at baseline and at 6 and 12 months. Total and individual isoflavone (daidzein, genistein and glycitein) intakes were calculated from diet records. The parent isoflavone compounds (daidzein, genistein and glycitein) and their metabolites (equol, O-desmethylangolensin (O-DMA), dihydrodaidzein and dihydrogenistein) present in the urine samples were analysed using liquid chromatography–MS. Intake levels of total and individual isoflavone compounds were significantly higher in the high isoflavone (HI) group than the levels in the low isoflavone (LI) group (P < 0·05). Urinary excretion of all isoflavone parent compounds was significantly higher in the HI group than in the LI group (P < 0·0001). Among isoflavone metabolites, only O-DMA and total metabolites were significantly different (P < 0·05). Total isoflavone intake was highly correlated with the urinary excretion of total parent compounds (r 0·68; P < 0·01), parent compounds plus their metabolites (r 0·66–0·69; P < 0·01) and total isoflavonoids (r 0·72; P < 0·0001). In conclusion, overnight urinary excretion of total isoflavonoids is a reliable biomarker of usual isoflavone intake in Korean girls of pubertal age.

We investigated the adverse effect of phytate on mineral absorption and the effect of dietary phytate and age on the relationship between faecal phytate and faecal mineral excretion. Fourteen young women (aged 19–24 years) and fourteen elderly women (64–75 years) were studied for two metabolic periods (MP). In MP1, the subjects consumed a controlled high-phytate (HP) diet for 10 d; in MP2, they were on a low-phytate (LP) diet for 10 d. In each period, diet samples and complete faecal samples for 5 d were collected to analyse phytate and mineral contents. Mineral concentrations in diet and faeces were measured by inductively coupled plasma–atomic emission spectrometry. Linear regression analysis was used to examine the associations between faecal phytate and mineral excretion. The degradation rate of dietary phytate was about 77 % for young women, which was significantly lower than that of elderly women (86 %) (P < 0·05). Faecal phytate excretion was positively correlated with mineral excretion (Ca, P, Fe and Zn) in both the HP and LP diet groups in young women (P < 0·05). The linear relationship tended to be greater during the LP diet period compared with the HP diet period in young women. However, no association was found between phytate excretion and mineral excretion in elderly women. In summary, undegraded dietary phytate (10–20 %) had a negative effect on mineral absorption in young women, and the relationship between faecal phytate and mineral excretion was affected by both dietary phytate and age.

The purpose of this study was to investigate the association between dietary patterns and sexual maturation among Korean children. A cross-sectional study was conducted in 422 boys and 365 girls aged 9–12 years living in Seoul, Korea. Three-day food records were obtained, and pubertal stages were determined with a questionnaire using Tanner stages. Body fat was measured by bioelectrical impedance analysis, and bone mass content at the right calcaneus was measured by portable dual-emission X-ray absorptiometry. Exploratory factor analysis with a Varimax rotation was applied to identify dietary patterns using twenty-four food groups. Four distinct dietary patterns – ‘rice and Kimchi’, ‘shellfish and processed meat’, ‘pizza and drinks’ and ‘milk and cereal’ – were obtained. Twenty-six per cent (24% stage 2, 2% stage 3) of boys had genital development, and 79% (63% stage 2, 16% stage 3) of girls showed breast development. In boys, genital development was weakly positively associated with ‘shellfish and processed meat’ dietary factor scores (odds ratio 1·65, CI 0·95, 2·89, pfor trend 0·07) after adjusting for confounders. In girls, breast development was significantly positively associated with the factor score of ‘shellfish and processed meat’ (odds ratio 1·88, CI 1·08, 3·26, p for trend 0·05). These results suggest that dietary patterns were related to body composition and sexual maturation among the Korean children. Further investigations are needed to identify components of the foods consumed in high amounts in these patterns and how they are related to sexual maturation.

Korea has experienced exceptionally rapid economic developments. Even though the country has managed to maintain aspects of its traditional diet, dietary habits are changing, especially among adolescents. This study was carried out to identify prevailing dietary patterns among Korean adolescents and to compare the nutrient intakes and dietary behaviours between the patterns. A 3 d diet record, collected from 671 Korean adolescents aged 12–14 years in Seoul, Korea, was assessed. By cluster analysis, subjects were classified into a modified (69·9 %) and a traditional (30·1 %) dietary pattern group. The modified group consumed more bread, noodles, cookies and pizza/hamburgers compared with the traditional group, which consumed mainly rice and kimchi (fermented cabbage). The modified group had significantly higher intakes of all nutrients. It had a higher total daily energy intake (7719 kJ), a higher daily energy intake from fat (29·8 %) and a higher cholesterol intake (326 mg/d), compared with the traditional group (6686 kJ, 24·8 % and 244 mg/d, respectively). The modified group was more likely to consume fast foods, fried foods and carbonated beverages even though they consumed more fresh fruits and milk, while the traditional group was more likely to have a rice-based diet and not to skip breakfast. These results suggest that monitoring dietary behaviours of adolescents, especially in a society experiencing a nutrition transition, is necessary in order to identify both negative and positive changes in respect of risk factors for nutrition-related chronic diseases as well as for undernutrition.