Eui-Hyun Yoon, et al: BMD and Food-frequency And frequency of milk and dairy product consumption was significantly associated with greater femoral neck BMD in men. These findings were consistent with previous studies.2,22) Tucker et al.2) concluded that potassium, magnesium, and vitamin C-rich fruits were associated with greater BMD. It is thought that fruit rich in potassium citrate metabolically generate base, which therefore buffers the acid produced by dietary protein of animal origin, conserving bone mineral.14) Magnesium also plays an important role in calcium metabolism. It is known that higher intake of magnesium was associated with lower bone resorption. Fruit is a principal source of potassium and magnesium and this finding emphasizes its potential role in prevention of osteoporosis. Several studies have identified the relationships between fruit intake and BMD.2,22) However, they had some limitations, for example, that the study population was limited to the elderly, or the sample size was small, or BMD was measured at limited sites. On the other hand, our study deals with a large sample size and a wide age-range of subjects. Also, BMD was measured at the femoral neck and lumbar spine, as this measurement site is recommended as the reference standard.23) We found that other carbohydrates showed significant association with BMD at the lumbar spine and femoral neck in women. However, there are few studies that examine associations between carbohydrate and BMD, and none showed a significant relationship.24) Since the evidence remains limited, further investigation of this relationship is needed. Milk and dairy products were shown to significantly and positively impact BMD at both the femoral neck in men in this study. That is compatible with the well established fact that milk and dairy products are great sources of nutrients needed in bone growth and maintenance since they are the principal source of calcium.25) However, in women, we could not identify an association between milk and dairy products and BMD. This may be due to the fact that absolute dietary intake amount of milk and dairy products were relatively smaller in women than in men. Further investigation into not only food frequency but also dietary intake amount in this relationship is needed. This study did not show a relation between vegetable intake and BMD, although several studies have shown a positive relation between vegetable consumption and BMD.2) A possible explanation may be that the tendency that unlike fruit, most vegetables in this study were consumed after being cooked.26) 292 | Vol. 33, No. 5 Sep 2012 During cooking with heat or by other procedures, lots of nutrients and vitamins that can positively impact BMD may be lost or much reduced. In previous studies, the reported effects of protein on BMD are conflicting. Sellmeyer et al.27) reported higher animal vegetable protein ratios influence greater bone loss at the femoral neck and more hip fracture. Protein has been associated with calcium loss. In contrast, Hannan et al.28) reported the protective effects of total protein and animal protein intake against bone loss in the Framingham Osteoporosis Study population. In our study, on the other hand, neither legumes, potatoes, meat or eggs, or fish groups-those groups mainly consisting of protein-showed a statistically significant association with BMD. However, in women, we could not identify the association between milk and dairy products and BMDs. This may be due to the fact that absolute dietary intake amount of milk and dairy products is relatively smaller in women than in men. Further investigation into not only food frequency but also dietary intake amount in this relationship is needed. Association between increasing seafood consumption and greater BMD was observed in some studies.26,29,30) These results can be attributed to the high content of essential fatty acid (EFA) present in fish. EFAs are known to enhance vitamin D effects and this may result in increased BMDs.31) But, in our study, we could not find association between fish consumption and BMDs. The effects of dietar y protein intake on BMDs are controversial. Higher-protein diets increase urinary calcium excretion and acidifying amino acids can stimulate bone resorption, then reducing BMD.32,33) However, as protein is a major constituent of bone, low protein intake is associated with frailty and fracture in the elderly.34) Recently, in a longitudinal study, higher protein intake did not have a negative effect on BMD in premenopausal women.35) However, in our study, we could not find association between protein consumption and BMDs. With regard to confounders, similar results with previous literatures were observed. BMI and physical activity were both positively associated with BMD. Current smoking showed a negative relationship with BMD. Alcohol drinking and BMD showed a positive association in women, which is consistent with previous reports36,37) that hypothesized this positive association to be caused by the effects of alcohol on adrenal androgens or Korean J Fam Med