Specific and nonspecific responses to fasting and refeeding differ in healthy young adult elderly persons - Immune Response to Fasting and Refeeding - Brief Article

Nutrition Research Newsletter, Nov, 2001

The decline in immune function with age is unanimously recognized and is supported by many epidemiologic and clinical observations. These age-related functional changes are responsible for the increased vulnerability to disease of the elderly which contributes to a higher prevalence of infectious and neoplastic diseases. This age-related increase in morbidity will be a major public health concern in the decades to come. The most consistent feature of the aging immune system is the heterogeneity of the changes observed. Nutritional status has long been recognized as a major factor in age-related immune impairment especially in elderly institutionalized persons. However, the specific interactions between malnutrition and aging on immune status remain poorly understood. The aim of this investigation was thus to study the aging effect by itself (with no disease-related or pharmacologic interference) on immunologic adaptation to nutritional changes. For this purpose, the researchers measured the effect of a 36-hour fasting period and of a four-hour re-feeding period on specific and nonspecific immune status in healthy elderly and young adult volunteers.

Seven young adult and eight elderly subjects took part in the study. Physical and biochemical examinations were performed according to the SENIEUR protocol to select adult and aged subjects in good health. Briefly, all volunteers were healthy, with no relevant acute or chronic disease that might affect the immune system. In particular, none of the subjects had cancer: serious cardiac, brain, liver, or kidney disease: or any sign of infection or inflammation, and none were taking drugs known to affect the immune system (anti-inflammatory drugs, hormones, and analgesics) or had recently been vaccinated.

After a 7-day stabilization period during which the subjects received a standardized diet (1.6 x predicted resting energy expenditure and containing 16 percent protein) to normalize energy intake, the subjects fasted for 36-hours. After this short period of starvation, liquid food was reintroduced gradually for 4 hours. The re-feeding diet contained 18 percent protein. 32 percent fat, and 50 percent carbohydrate. This dietary intake corresponded to one meal consisting of one-third of the daily energy consumption. The diet was supplied in liquid form to optimize gastric emptying and facilitate nutrient absorption. All the subjects were kept under strict medical supervision during the experiment. Blood samples were collected at the end of the pre-fasting period (at 0700, 10 hours after the last meal) for the measurement of basal values, at the end of the fasting period, and after 4 hours of re-feeding.

The researchers found marked differences between adult and elderly healthy individuals in both the number of some lymphocyte subsets and neutrophil functions. The results of the present study show that age by itself affected not only basal immune function but also the response to various nutritional states, implying that nutritional state is an important consideration in the clinical management of elderly patients. The results indicate that basal counts of total T lymphocytes and the cytotoxic T lymphocyte subset were lower in the elderly than in the adult subjects. For natural killer lymphocytes, there was a significant decline in the CD3-CD16+CD56+ phenotype (immature cells) with age. Such an immunosenescent change in the immature natural killer cell subset is a potential immunologic disadvantage for elderly subjects because these lymphocytes have high cytotoxic potential.

In conclusion, despite the limited number of subjects in this study, the researchers showed that short-term fasting and re-feeding affect several immunologic indexes in elderly persons. in whom aging already favors intrinsic changes in immunity. The mechanisms of the impairment in the ability of lymphocytes and neutrophils to adapt to nutritional manipulations are still a matter of speculation. This may involve either an intrinsic defect in the immune cells that exist before the cells are released into the bloodstream or an acquired defect related to environmental components depending on both the aging process and nutritional status. These findings highlight the specific effects of age and nutritional state on immune function and suggest that age is a risk factor for reduced immunity, even in a healthy population. In this population, protein-energy supply or even specific immunomodulating nutritional agents must be carefully administered to aid the recovery of immune function and limit the consequences of infectious challenge.

S. Walrand, K. Moreau, E Caldefie, A. Tridon, J. Chassagne, G. Portefaix, L. Cynober, B. Beaufrere, M. Vasson, Y. Boirie. Specific and nonspecific immune responses to fasting and re-feeding differ in healthy young adult and elderly persons. American Journal of Clinical Nutrition 74 (November 2001) [Correspondence: S. Walrand, Laboratoire de Biochimie, Biologie Moleculaire et Nutrition, Faculte de Pharmacie, 28 place Henri-Dunant, BP 38, 63001 Clermont-Ferrand Cedex 1, France. E-mail: stephane.walrand@u-clermont.fr]