The Frequency and Amount of Fish Intake Are Correlated with the White Blood Cell Count and Aerobic Exercise Habit: A Cross-sectional Study

OBJECTIVE: We investigated the relationship between the amount and frequency of fish intake, and the white blood cell (WBC) count and aerobic exercise habits. METHODS: We conducted a cross-sectional study between April 2019 and March 2020 at the Health Planning Center of Nihon University Hospital on a cohort of 8,981 male subjects. RESULTS: The average amount and frequency of fish intake were 134±85 g/week and 2.14±1.28 days/week, respectively. The WBC count decreased significantly as the amount of fish intake increased (p<0.0001). According to a multivariate regression analysis, a high fish intake amount (β=-0.082, p<0.0001) and regular aerobic exercise (β=-0.083, p<0.0001) were independent determinants of a low WBC count. The proportion of subjects engaged in regular aerobic exercise increased with an increase in the amount of fish intake (p<0.0001). Furthermore, the amount and frequency of fish intake significantly correlated with the amount of n-3 polyunsaturated fatty acid intake determined using the Japan's National Nutrition Survey results (both r=0.962 and 0.958). Therefore, the amount of fish intake could be substituted by the average number of days of fish intake per week. CONCLUSION: A high fish intake was an independent determinant of a low WBC count and engagement in regular aerobic exercise, regardless of whether the fish intake was defined by the amount or frequency of fish intake. However, since fish intake frequency can be measured more easily, this may be used to measure the fish intake.