Changes in dietary intake account for seasonal changes in cardiovascular disease risk factors

(1) to compare dietary intake in summer and winter time; (2) to measure the change in body mass index (BMI), blood pressure and serum cholesterol between winter and summer; and (3) to determine the relationships between seasonal differences in dietary intake and BMI, blood pressure and serum cholesterol measurements.

Ninety-four male industrial employees were screened twice in one year, in their work place, at winter and summer time. Workers were recruited from two factories and response rate was 95%. Health-related variables, including dietary intake, blood pressure and serum cholesterol were evaluated at each season and were compared. Correlation coefficients between seasonal differences in dietary intake and in BMI, blood pressure and serum cholesterol were calculated.

From summer to winter the mean values of BMI increase from 26.1 kg/cm2 to 26.6 (P=0.038), systolic blood pressure from 119.6 to 121.6 (P=0.025), diastolic blood pressure from 75.2 to 77.2 mmHg (P=0.001), total cholesterol from 200.8 to 208.6 mg/dL (P=0.001), LDL cholesterol from 125.2 to 134.9 (P=0.001) and HDL cholesterol from 42.7 to 44.3 (P=0.0084). Triglycerides levels decrease from 174 to 145 in the winter (P=0.03). Mean dietary intake of fat increases from 99.1 to 106.0 (P=0.0016), saturated fat from 43.6 to 46.3 (P=0.0137), polyunsaturated fat from 25.1 to 28.3 (P=0.0002), cholesterol from 462.0 to 497.9 (P=0.0313), sodium from 5778.5 to 8208.2 (P=0.0035), zinc from 11.6 to 12.3 (P=0.0001), vitamin B1 from 1.4 to 1.5 (P=0.002), vitamin D from 4.3 to 4.9 (P=0.0323) and vitamin E from 11.2 to 12.7 (P=0.0073). Significant correlation was shown between the seasonal increase in saturated fat and the increase in BMI (r=0.37), total cholesterol (r=0.21) and LDL cholesterol (r=0.29). Seasonal change in dietary cholesterol intake was significantly and positively correlated with serum total cholesterol (r=0.24) and LDL cholesterol (r=0.24). Blood pressure was not associated with nutritional intake variables.

Dietary intake in summer and winter is different as well as blood pressure, BMI and serum cholesterol. The seasonal increase in fat and cholesterol intake at winter time is associated with changes in BMI and serum cholesterol.