The Effects of a Nutrient-Enriched Bar on Host Defense Mechanisms and Immunogenicity of Hepatitis A Vaccine During US Army Ranger Training

Abstract : This study was designed to assess the effects of a nutritionally enhanced food bar and intense, protracted stress as engendered by U.S. Army Ranger training on immune function as measured by immunogenicity to Hepatitis A vaccine, leukocyte phenotype, and delayed type hypersensitivity reaction. The stress of Ranger training caused a number of immunological changes from baseline, and the group consuming the bar fortified with antioxidants, indigestible carbohydrate, zinc, copper, selenium and other trace elements and vitamins manifested decreased effects on their immune function. For example, there was an attenuated reduction of the number of monocytes in the soldiers in the treatment vs. a placebo group with a likewise decreased reduction of T-lymphocytes in the treatment group. Other markers, such as body weight changes and numbers of B-lymphocytes, while not significant, indicated a clear trend toward beneficial effects in the treatment group. Hepatitis A vaccine was administered to both groups. The stress of Ranger training caused approximately a 30% reduction in antibody response when compared to a non-stressed group, but consumption of the nutritionally enriched bar had no significant effects on this response. Over 70% of those who completed this rigorous training rigorous believed that supplementation with the bars, both treatment and placebo, helped them in completing Ranger training. While previous Ranger trainees had manifested significant weight loss during this training, the current class actually showed a weight gain. Generally, these results indicated that the experimental bars increased immune competence and status, contributed to a gain in weight during the training, and were very well tolerated and accepted by the training population.