Only healthy subjects were chosen for the study in order to avoid the confounding effects on the immune system of disease or medications. After a 36-hour fast, 7 young adult (mean age 24 years) and 8 elderly (mean age 71 years) participants were given a liquid meal of standard nutritional composition. Serum samples obtained before the fast began had indicated that the white blood cell count, an indicator of immune function, was 17.4% lower in the elderly subjects than in the young adults. Once the subjects had taken a standardized meal after fasting, the young adults had a 5.8% increase in white blood cell counts. In contrast, the elderly subjects experienced a nonsignificant decline in their white blood cell counts that were not restored by refeeding. A significantly lower level of white blood cell function was observed in the elderly in comparison to the young adults after refeeding.
The failure of the elderly subjects' immune systems to respond to refeeding underscores the risk posed by poor nutritional status in elderly patients, a risk that may be amplified by infection, inflammation, or disease. In an accompanying editorial, Stephensen comments on the effective design of studies on nutrition and the immune system and the importance of first assessing the underlying health of the subjects in research that measures immune response.
Walrand, Stéphane et al. Specific and nonspecific immune responses to fasting and refeeding differ in healthy young adult and elderly persons. Am J Clin Nutr 2001;670-8.
Stephensen, Charles. Examining the effect of a nutrition intervention on immune function in healthy humans: what do we mean by immune function and who is really healthy anyway? Am J Clin Nutr;74:565-6..
This media release is provided by The American Society for Clinical Nutrition to provide current information on nutrition-related research. This information should not be construed as medical advice. If you have a medical concern, consult your doctor. To see the complete text of this article, please go to:
http://faseb.org/ajcn/November/13150-Stephensen.pdf
For more information, please contact: stephane.walrand@u-clermont1.fr or cstephensen@ucdavis.edu
American Journal of Clinical Nutrition