Relationships of physical fitness, fatness, and lifestyle indicators with blood iron in children and adults

The associations between physical fitness, fatness, activity level, dietary intake and smoking, with indicators of blood iron status are considered in 1,216 children and adults of the Quebec Family Study, 612 males and 604 females, classified into six age groups: 10–14, 15–19, 35–39, 40–44, 45–49, and 50–54 years. Physical fitness was determined as power output at a heart rate of 150 beats per min on a cycle ergometer (PWC 150 ) and as strength of the knee extensor muscles. Fatness was estimated with the body mass index (BMI) and the sum of six skinfolds. Activity level and dietary intake were assessed with three‐day records. Hemoglobin concentration (Hb), hematocrit (Hct), and serum ferritin of males were greater ( P < 0.001) than those of females in all age groups except 10–14 years. Serum ferritin of boys and girls (10–19 years) was significantly lower than in adults. There were no clear relationships between Hb, Hct, and serum ferritin with activity level, physical fitness and body composition. However, smoking was positively correlated with Hb ( P < 0.01) and Hct ( P < 0.001) in all age groups, except adult females 35–39 years. Using a multiple correlation procedure, the independent variables of the study accounted for about 9% (adult males), 11% (boys), 11% (adult females), and 5% (girls) of the variance in serum ferritin. Thus, activity level, nutritional intake, physical fitness and body fat are only marginally related to blood iron status in this population. © 1995 Wiley‐Liss, Inc.