Objective: To test the hypothesis that older men who consumed a vegetarian (lacto-ovo) diet would develop a lower iron status compared with older men who consumed a beef-containing diet during a period of resistive training (RT).
Design: Experimental, repeated measures study.
Subjects: Twenty-one healthy men aged 59 to 78 years, with a BMI range of 24 to 33 kg/m(2), completed the study.
Intervention: All men consumed a vegetarian diet for 2 weeks (baseline). After this, the men were randomly assigned to one of two dietary groups. Eleven men consumed a beef-containing diet, and 10 men continued to consume a vegetarian diet for 12 weeks. During this time all subjects participated in RT three days per week, designated as RT1 to RT12.
Main outcome measures: Serum ferritin and serum iron concentrations, transferrin saturation, transferrin receptor, total iron binding capacity, and selected hematological variables, as well as selected nutrient intakes and estimated iron bioavailability from three-day diet records, were determined at baseline, RT5, and RT12.
Statistical analyses: A general linear model repeated-measures ANOVA was used to examine the effects of group, time, and group x time interactions for iron status and dietary data.
Results: Total iron intake was not different between the two groups; however, the beef group had a three to four times greater intake of bioavailable iron (P<.01) than the vegetarian group. Serum iron, total iron binding capacity, transferrin saturation, and transferrin receptor were not significantly different between the beef and vegetarian groups, or changed over time with RT. Serum ferritin decreased over time in both the beef and vegetarian groups during RT (P<.01). Re-introduction of beef into the diets of the beef group increased hemoglobin concentration and hematocrit compared with the vegetarian group during the 12 weeks of RT (group x time, P<.05). These changes were within clinically normal limits.
Applications/conclusions: Older men who consume a beef-containing, higher-bioavailable-iron diet, compared with a vegetarian, lower-bioavailable-iron diet, have an increased hematological profile during a 12-week period of RT. Older men who consume either a beef-containing or a vegetarian diet maintain a hematological profile within clinically normal limits during 12 weeks of RT.