beta-Carotene increases monocyte numbers in peripheral rat blood

The purpose of this study was to determine changes in leukocyte numbers in peripheral rat blood after varying dietary beta-carotene intake. Thirty male weanling Sprague-Dawley rats were fed ad libitum a vitamin A deficient defined nutrient chow, adequate in all other nutrients. Rats were randomly placed in a group with beta-carotene added to the chow as the vitamin A source. Group 1 was completely deficient, Group 2 had 1 microgram beta-carotene/g chow, the control group, and Group 3 received 25 micrograms beta-carotene/g chow. Before beginning the experimental diets and after two weeks, a blood sample was taken from the tail vein for a differential white blood cell count. Animals were sacrificed by cervical dislocation, and the spleen and thymus were removed and weighed. There was a statistically significant increase in monocyte numbers in Group 3, and a positive correlation between beta-carotene intake and monocyte numbers. Beta-carotene may affect monocyte numbers, a potential mechanism of action in cancer prevention.