Nutrition and Immune Function in the Elderly
Strengthening Immunity by Nutritional Supplementation
Oct 6, 2009
Immune function relates to the capability of the body to resist infections. There are two types of immunity. Innate immunity consists of natural physical and physiological barriers to the entrance of pathogens. Acquired immunity is a result of prior exposure to pathogens or their antigens, that causes activation of specialized immune cells. These cells are known as B-lymphocytes, which can differentiate into antibodies, and T-lymphocytes.
The Decline in Immune Function in the Elderly is Known as Immune Senescence.
The elderly are particularly susceptible to infections due to a decline in immune function with age. The infections also tend to have more severe consequences. Aging results in declines in lymphocyte functioning and proliferation, reductions in antibody formation, and declines on hormones necessary for thymus gland functioning. Environmental factors leading to declines in immune function include certain drug use, and deficiencies in nutrients required for immune function. These deficiencies can be due to a reduction in food intake, as well as a reduced absorption and metabolism of nutrients. Active infections can increase the requirements for certain nutrients, and concomitant diseases can increase the morbidity of infections.
The Role of Nutrients in Maintaining Immune Function in the Aged
Protein deficiency is associated with decreased acquired immune response, while deficiencies in the amino acids arginine and glutamine result in immune changes similar to those seen in the elderly. Most micronutrients (vitamins and minerals) have a range of levels for optimal immune function. Whereas a minimal amount can be defined for effective function, beyond a certain level no further benefits are realized, and the benefits can even be reduced. This suggests that megadose levels of micronutrients could even be detrimental for immune function. Vitamin A maintains the integrity of mucus-secreting cells, as well as enhances production of immune cells. Vitamin C may act primarily as an antioxidant. Low levels of vitamin E are directly related to an increase in the number of infections. Vitamin B6 deficiency results in atrophy of lymphoid tissue and decreased antibody production. Zinc serves essential functions in a wide variety of immune components, and even a marginal deficiency can have large effects on immune function, resulting in a higher incidence in microbial infections.
A combination of modest nutritional deficiency and decreased immune function acts synergistically on health in which each component has a greater effect than either component alone. Acquired immunity is more sensitive to micronutrient deficiency than is innate immunity. Infection can increase nutrient requirements due to a combination of reduced intake (poor appetite), reduced nutrient absorption through the intestine, and increased metabolic demands of the body.
Studies on Micronutrient Supplementation
There have been relatively few studies on the effect of micronutrient supplementation on immune function. The studies are difficult to perform, and need to be long-term lasting a year or more. Here are a few examples.
- An extensive survey showed that more than 60% of healthy adults over the age of fifty had deficient dietary intakes of Vitamins D and E, folic acid and calcium.
- Another study showed that 80% of elderly residents 79 years of age or older had inadequate intakes of four or more nutrients.
- A modest multivitamin-mineral was given to men and women over 65 years of age for a one year period. During the year, the supplemented group had only one-half the number of sick days compared to the unsupplemented control group.
- A study of elderly persons showed that taking a multivitamin for one year resulted in a stronger immune system, and higher blood levels for several vitamins. The study suggested that the current recommendations for older adults may be too low.
- A two-year study in a nursing home involved giving patients zinc and selenium, or Vitamins C and E and beta-carotene, alone or in combination. Patients who were supplemented with the minerals, with or without the vitamins had fewer respiratory or urogenital infections compared with the unsupplemented control group.
Strengthening Immune Function in the Elderly by Supplementation
Immune senescence is the term applied to the phenomenon of declining immune function in the elderly. The immune system within the body becomes less responsive and vigorous with advancing age, and many associated factors, such as poor dietary habits and concomitant disease conditions aggravate the problem. Micronutrient supplementation can play an important role in the overall medical program of the elderly. A daily supplement is most convenient, but there is a range of optimal levels of micronutrients, and megadose levels may be detrimental.
References
- Ahluwalia, N. "Aging, Nutrition and Immune Function."J Nutr Health Aging. 2004;8(1);2-6.
- Barnes, D. "Nutrition and Aging: Supporting the Aging Immune System." Standard Process.
- Chandra, RK. "Nutrition and the Immune System: An Introduction." Am J Clin Nutr 1997; 66: 460S-3S.
- Dickinson, A. "Benefits of Nutritional Supplements: Immune Function in the Elderly." From: The Benefits of Nutritional Supplements. 2002. Council for Responsible Nutrition.
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