Eui-Hyun Yoon, et al: BMD and Food-frequency Table 2. Weekly intake frequency* of each food groups. Food group Men (n = 18,069,970) Staple carbohydrates 27.3 ± 0.0 Other carbohydrates 4.2 ± 0.0 Legumes 7.9 ± 0.0 Potatoes 1.7 ± 0.0 Meat and eggs 6.0 ± 0.0 Fishes 2.3 ± 0.0 Vegetables 32.8 ± 0.0 Seaweeds 3.5 ± 0.0 Fruits 7.6 ± 0.0 Milk and dairy products 4.1 ± 0.0 Instant foods 0.9 ± 0.0 Values are presented as mean ± SD. *Food-frequency: weekly food frequency, times/wk. †P-value by Student t-test after weighting by wt_tot. Women (n = 18,433,574) 29.3 ± 0.0 4.0 ± 0.0 9.5 ± 0.0 1.9 ± 0.0 5.2 ± 0.0 2.2 ± 0.0 31.5 ± 0.0 3.9 ± 0.0 9.9 ± 0.0 4.7 ± 0.0 0.7 ± 0.0 P-value† <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 artery diseases and diabetes, and use of calcium or vitamin D supplement. International Physical Activity Questionnaire score21) was used to classify each subject’s physical activity. For alcohol drinking, subjects were asked to quantify their weekly intake of alcohol drinks. From this information, based on 10 gm alcohol per drink, total grams of alcohol consumed per year was estimated. Intake of calcium or vitamin D supplements were coded as yes-no variables. For women, an additional reproductive questionnaire was asked on menstrual and reproductive history, including age at menarche, age at menopause and postmenopausal period, estrogen use for hormone replacement therapy (HRT), as well as current and past oral contraceptive use. 5. Statistical Analysis All analyses were performed by reflecting weighted values at the stratification of the samples applied to the KNHANEs. The characteristics of the study subjects were compared using the Student t-test and the Pearson χ2 test. Multiple linear regression analyses adjusted for age, BMI, physical activity, smoking and alcohol drinking, other diseases, vitamin or mineral supplements, and estrogen use were used to evaluate the relationship between the food frequency and the BMD. A P-value of less than 0.05 was considered significant. All statistical analyses were performed 290 | Vol. 33, No. 5 Sep 2012 with SPSS ver. 18.0 (SPSS Inc., Chicago, IL, USA). RESULTS General characteristics of subjects are presented in Table 1. The average age for men was 43.8 years and for women was 45.8 years. The average BMI for both men was 24.1 kg/m2 and women was 23.1 kg/m2. Proportionally more men than women were current smokers, and consumed much more alcohol. More women than men used supplements of vitamin or minerals. With statistical significance, the histories of hypertension, cerebrovascular accidents, and coronary artery diseases were higher in men whereas rheumatoid arthritis and thyroid diseases were higher in women. In women, mean age of menarche was 14.5 years, and average postmenopausal period was 14.0 years. Postmenopausal women have received HRT with estrogen for 1.8 months on average. Total period of using oral contraceptives in adult women was 2.3 months on average. Mean BMDs ranged from 0.83 g/cm2 for femoral neck to 0.97 g/cm2 for lumbar spine in men and from 0.71 g/cm2 for femoral neck to 0.92 g/cm2 for lumbar spine in women. The food-frequencies of each food group are shown in Table 2. There is a statistically significant male predominance in the food-frequencies of other carbohydrates, meat and eggs, fishes, Korean J Fam Med