Adequate and balanced nutrient intake is necessary to maintain the health of the body as well as of the mind and to prevent diseases. Also, the establishment of proper dietary habits is very important for desirable nutritional practices. Proper dietary habits can decide physical and psychological health status of individuals, thus poor dietary habits not only impair physical growth but also greatly affect the emotional development [1].

College students are no longer under the supervision of their parents for their dietary life and may face many problems in the quality of their diets when they become to manage their lives independently without receiving proper education on dietary life [2]. Also, dietary behavior of college students is very sensitive to the changes of social environment and going towards much undesirable directions such as irregular meals, frequent meal skipping, eating out and overeating, excessive drinking and smoking that are affected by class schedules without considering meal time, increased free time, part time job, and get-together with friends and dating [3].

These could be confirmed from the results of regional survey [4,5] in college students that equivocally pointed large numbers of cases which caused obesity or underweight, anemia, gastrointestinal tract diseases, and nutritional imbalance by unbalanced intake of mainly cheap, convenient, and preferable foods rather than focusing on nutrition or hygiene due to dietary habits such as irregular meals, meal skipping, overeating, deviated food habit, late night snack, excessive intake of ready-to-eat products, excessive smoking and drinking, limited pocket money, and lack of nutritional knowledge.

While the smoking rate of men and women of 19 years and older has been decreased recently by 39.6% and 2.2%, respectively, in Korea, the smoking rates of men and women between 20-29 years were reportedly higher as 40.9% and 5.9%, respectively, than those of other age groups [6]. Not only smoking but also free radicals that are generated inside the body by carbon monoxide, nicotine, and tar contained in the cigarette itself are elucidated as risk factors for various diseases [7]. This smoking habit could even increase the chance of drinking, which ultimately changes dietary habit and life style, further affects nutrition and health status of the body.

Metals play important roles in numerous physiological actions inside the body, but if heavy metal concentrations are in excess above the normal level, these can threaten the health. Heavy metals are substances with specific gravity more than 5g/cm³ and have been used for several thousand years, and can induce various diseases when inhaled or ingested through either air or food stuffs. Heavy metals, after being absorbed and bound to tissues, are not easily excreted from the body, and their accumulation is increased by age due to their long half-life, ultimately causing various health defects [8]. Major heavy metals that threaten health include cadmium, lead, and mercury [9]. It has been known that elevation of blood cadmium level, by increasing systolic blood pressure as well as diastolic blood pressure increased the risk of hypertension [9]. Acute lead poisoning induces headache, unstable emotion, abdominal pain, and various symptoms related to the nerves, and it has been known that chronic exposure to lead further develops renal tubule damages [8].

This study was conducted to provide the data which can be a database in improving dietary habit as well as lifestyle of college students in Korea by finding out current address of health status of college students and related factors through investigating difference between males and females in physical characteristics, health related factors, dietary habit, heavy metal levels in blood, and other blood profiles.

The general characteristics of subjects in this study revealed that the age of male students was higher than that of female students, and male students had less family members. Residence type showed a higher rate in residing either in a dormitory, self-boarding arrangement, or at a boarding house, in the case of male students. In female students, there was a higher rate of residing at home. The higher rate of staying at home in female subjects was similar to the report in which a higher residing rate at home was found in female students than in male students, with no significant differences in the research about the nutritional intake. This rate was also subjected to college students in Daejeon, Korea [12]. The significant difference in residence type between male and female students might be due to regional location difference of the subjects' area.

The mean height and weight among anthropometric measurements of subjects were compared with the Anthropometric standards for age 19-29 as per Dietary Reference Intakes for Koreans [13]. The height of both male and female students was nearer to the standard, the weight of male students was within the heavier range than the standard, whereas the weight of female students was lighter than the standard. The mean body weight of male students in this study was even heavier than that of male students from Gwangju [14]. The mean Body Mass Index(BMI) was in a normal range for both male and female students, but was still higher than those values of students from Daejeon for males (21.5 kg/m²) and for females (19.1 kg/m²) [15], and for males (21.7 kg/m²) and for females (19.6 kg/m²) [12], measured in two separate studies. Also, per the BMI standard set by the Korea society for the study of obesity subjected to Asian adults [11], the body mass index below 18.5 was classified as underweight, 18.5- below 23.0 as normal weight, and more than 23 as overweight. As a result, 51.2% of male students and 13.5% of female students in this study were found to be overweight, meaning more than half of the male students were overweight. Also, the underweight group was higher in female students (16.2%), while a smaller percentage of male students (2.3%) was in the state of being underweight (P < 0.01). When compared with the results conducted with students from Daejeon [11], the percentage of the underweight group was higher in females (27.7%) as against males (4.7%), overweight was higher in male students (25.2%) than in female students (6.2%). The overweight percentage of male students in this study was particularly high.

Systolic pressure and diastolic pressure, lean body mass, and skeletal muscle mass were all significantly higher in male than in female students (P < 0.001). However, Percentage body fat in female students was higher than in male students (P < 0.001). Percentage body fat in male students (18.8 ± 6.4%) and female students (28.6 ± 5.8%) had higher levels over the normal range [16]. In this study, the percentage body fat in female students was particularly higher than that of female students from Gwangju [14]. In the case of female students, although their body mass index was normal, since they were more likely to overestimate their weight, they need to have a proper conception about body type and receive nutritional education in order to control their body types.

Male students were engaged in exercise more frequently than female students (P < 0.05). Though there was a difference in the research findings about regular exercise practiced by students, such that no difference was found in the frequency of exercise between male and female students from Busan [17], similar differences existed in the research subjected to college students from Chungcheongnam-do [5]. However, most of the students engaged in exercise for 1-4 times a week with no difference between genders. In the research finding subjected to the students from Daejeon [12], the exercise frequency of male and female students were similar in both genders as on an average for male (3.6 times a week) and female students (3.8 times a week).

In the rate of drinking, there was no significant difference in gender, as 86.0% of male and 64.9% of female students drink alcohol. The drinking rate was more or less lower than that of the results conducted with students from Chungcheongnam-do, where 92.8% of male students and 91.5% of female students drink [5], and 91.6% of male students and 83.7% of female students drink in another study [12], which is a large number of students involved in drinking. It has been known that drinking makes meal intake not as sufficient, changes lifestyle and dietary habits, thereby badly affecting nutrition as well as the healthy state of body. Moreover, since there is large interrelationship between smoking and drinking (smokers have a high drinking rate), the smoking amount as well as the drinking amount correlate with each other [18]. The drinking frequency of male students is significantly higher than that of female students (P < 0.001). Though drinking frequency in female students was lower than that in male students, approximately half of the female students drink more than once a week, which reflects the high drinking practice in young woman. High drinking frequency could have been attributed by the residence type, as more than 50% of students are lodged either in dormitories or self-boarding. This result seems to appear as a problem since Korean college students did not receive proper health education amidst the competition for the college entrance examination. They were also liberated from parental control all of a sudden, and had to manage his/her life independently [1]. It is supported by the fact that the score of health improvement practice in students residing in dormitory was significantly lower than that of students living at home [19]. Therefore, a systematic education is required in order to maintain proper life and health control for students in Korea.

The smoking rate was 37.2% in male students, whereas it was 0% in female students (P < 0.001). The smoking rate in this study was lower than the rate of 59.8% in males and 1.7% in females from Daejeon. 62.5% of male smoker students smoked on an average 10-19 cigarettes a day, which was a similar level as the report by Rhim et al. [20].

In the investigation of dietary habit of subjects, the highest score was found in 'intake balanced diet'; the scores for 'not adding salt or soy sauce in dishes' and 'less intake of sweet foods containing high amount of sugar' were high. This result could be regarded as a similar trend in the research result conducted with college students from the Mid-Western USA [21]: 66.4% of respondents answered as 'Yes' and 'Very much likely' for the balanced diet question, which gives an idea of high cognition as to the balanced diet by students. Lower scores were obtained in 'considering calories while eating out' and 'considering calories at table'. This result could be related with the overweight level of more than 50% of the male students in this study. Nutrition education about calorie intake might be required. The questions associated with calorie intake (such as 'eating while calculating calories', 'considering calories during eating out', 'read nutrition label before purchasing foods, and 'prefer cooked foods with low calorie (steam/grill) recipe' showed higher scores in female students than male students (P < 0.001-P < 0.01), reflecting that female students are more aware of calorie intake and managing a dietary life. The dietary habit score was significantly higher in female students (2.86 ± 0.55) than in male students (2.54 ± 0.54) (P < 0.05). It has been reported that dietary habits of male and female students from Daejeon exhibited desirable changes in male students, whereas changes in female students were not as desirable as changes in male students [22]. In a later study about the dietary habits of college students, dietary habits of female students was better than that of male students [14], similar to the result as those in this study. However, since dietary habits of both male and female students are not desirable, shown in the poor dietary habit scores, dietary improvement education should be executed in order to improve nutrition and health for college students.

Plasma cadmium level of subjects did not show a gender difference, while higher plasma cadmium level was reported in female adults from the city center [23]. From the survey results of the nation's plasma heavy metal level conducted by the Ministry of Environment, the plasma cadmium level from these subjects was lower than the average level. 1.46 µg/L of average cadmium level was reported in the subjects in their 20s [24], and levels of 1.21 µg/L and 1.66 µg/L was reported in adult men and women living in city centers [23], which is far lower than the 5 µg/L recommended by WHO [25]. However, the cadmium levels of male and female students in this study were higher than the measured level 0.06 µg/L from middle school students [26]. Since cadmium is absorbed into the body through digestive organs and respiratory tracts during a person's growth, it has been reported as being associated with age and smoking; Accumulation of heavy metals with long half life in body is increased with age [27]. In this study, plasma lead level of male students was significantly higher than that of female students (P < 0.001). This result is in conformity with the survey research of adults living in city centers [23]. Plasma lead level in male students in this study is below the average lead level (2.25 µg/dL) of people in their 20s reported in plasma heavy metals level conducted by the Ministry of Environment, Korea during the year 2006, and WHO recommended value (20 µg/dL) [25].

The plasma cadmium and lead levels of smokers were significantly higher than those of nonsmokers in this study (P < 0.05). Many researches have reported a similar increasing effect of smoking on the plasma cadmium level and lead levels [8, 28]. It has been known that large amounts of cadmium and lead are contained in cigarettes, and these heavy metals are absorbed into the body through smoking and are concentrated inside the body tissues. Also, researchers suggested that plasma cadmium concentration and biophysical indices (mobility, density, and survival capability) of male sperms are inversely proportional to each other. Furthermore, high plasma cadmium level can be a cause of oligo-astheno-tetratozoospermia syndrome [29]. In addition, the necessity of research has been raised as to the correlation for the effect of heavy metal level increases on skeletal health along with the decreased intake of fruits and vegetables due to smoking [30].

In blood clinical indices other than heavy metals from male and female students, the number of red blood cells, hemoglobin, hematocrit level, and mean corpuscular hemoglobin concentration (MCHC) were significantly higher in male students than in female students (P < 0.001). The number of platelets was significantly higher in female students (P < 0.001) than in male students. When the anemia related indices of subjects were compared with the anemia assessment by the WHO [31], both male as well as female students showed normal levels. Plasma calcium and iron levels of male students were significantly higher than those of female students (P < 0.05).

Blood clinical indices of subjects by smoking showed that the number of red blood cells, number of white blood cells, hemoglobin level, and hemacrit levels in smokers were significantly higher than those of nonsmokers (P < 0.001-P < 0.05). The smoking effect on the increase of hemoglobin level could be confirmed as these results were in agreement with the report by Kwak et al. [32]. Increase in the hemoglobin level may be due to an enhancing effect of red blood cells and platelet biosynthesis, triggered by increases in carbon dioxide concentration and decreases in oxygen partial pressure in the blood [33]. Beser et al. [34] reported that hematocrit of men and women smokers was significantly higher than that in nonsmokers. When a smoker gave up smoking, the hemoglobin level, hematocrit level, and number of white blood cells have been decreased.

As shown from the results, it was found that there is a clear distinction in the physical characteristics between male and female students, higher muscle mass was observed in male students whereas higher percentage of body fat were found in female students. In dietary habits, there was also a difference between gender with high scores obtained from female students. The plasma cadmium level did not show a difference between male and female students, but a higher level of lead was found in male students. There have been differences between male and female students in their physical characteristics, dietary habit, and blood profile. Therefore, nutrition education programs and educational materials for college students should be developed in order to suggest positive changes in students' lifestyles and dietary habits.