Immunology
(See Table 4 for a summary of the following immunology related studies.)
The immune system often weakens with age, making the elderly more susceptible to infection and illness. As a result, illness is the fourth most common cause of death in the elderly. Yet, one quarter of the elderly have immune systems as strong as younger people. What determines the difference? One possible factor may be nutritional status.
In this double-blind study from Johns Hopkins University, Maryland, 96 healthy, elderly Canadians over age 65 were randomly assigned to receive either a multiple vitamin supplement or placebo. The vitamin supplement contained numerous vitamins in amounts similar to recommended daily allowances in the U.S., except for vitamin E and beta-carotene, which were about 4 times the usual dietary intakes. At the beginning of the study and after 12 months of the trial period, blood samples were taken and tested for numerous immunological factors, including T and B cell count, immune response, and natural killer cell activity. Subjects also notified the researchers every time they became ill. Subjects who became ill received immediate medical attention and treated appropriately with antibiotics and other supportive measures. Also, every 2 weeks throughout the study, the researchers conducted personal interviews to document additional occurrences of illness and infection.
After analyzing the data, researchers found that the supplemented group enjoyed significant benefits. For instance, compared to the control group, the duration of illness of those taking the supplements was much lower (average 23 vs 48 days per year). The number of days antibiotics were prescribed was also much lower (average 18 vs 32 days). The supplemented group also enjoyed significantly improved immune cell parameters including increased number of T and natural killer cells, natural killer cell activity, antibody response, and interleukin-2 production and release. Moreover, those who initially showed deficiencies in vitamin status but were corrected back to normal due to the supplementation showed the greatest improvement in immune cell status.
The researchers conclude the results support the hypothesis that nutritional factors are important for immune function. They also suggest large amounts of vitamins do not seem to be necessary for positive results and may even be counterproductive.
Chandra, R. Effect of Vitamin and Trace-Element Supplementation of Immune Responses and Infection in Elderly Subjects. Lancet. Vol. 340, pp.1124-7, 1992.
The goal of this study from the USDA Human Nutrition Research Center on Aging at Tufts University was to determine whether vitamin E supplementation enhanced immune status in healthy, elderly subjects over age 65. Eighty-eight subjects were randomly assigned in a double-blind fashion to take 60, 200, or 800 mg vitamin E (synthetic"dl-alpha-tocopherol in soy oil") or placebo (soy oil) daily for 235 days. At regular intervals, blood samples were taken and measured for vitamin E serum levels and various immunological factors. Immune response was tested using the delayed-type hypersensitivity skin response (DTH), a test measuring immune response to a minor infectious stimulant applied to the skin. Also, antibody response to various infectious agents such as tetanus, diphtheria, and hepatitis B virus was tested in vitro. The main results are:
- The 200 mg vitamin E group had a 65% increase in DTH and a 600% increase in antibody response to hepatitis B virus.
- The 800 mg vitamin E group had a more modest 49% increase in DTH and 250% increase in response to hepatitis B.
- The 60 mg vitamin E group had a 41% increase in DTH and 300% increase in response to hepatitis B.
- The placebo group had 17% increase in DTH and 300% increase in response to hepatitis B.
- No adverse effects to vitamin E supplementation were observed.
The authors conclude,"Since age-associated decline in immune response is associated with increased morbidity and mortality in the elderly and is widely observed, recommendations to increase the intake of vitamin E for elderly should be considered."
Meydani, S., Meydani, M., Blumberg, J. Vitamin E Supplementation and In Vivo Immune Response in Healthy Elderly Subjects. Journal of the American Medical Association. Vol. 277, pp.1380-6, 1997.
Allergic reactions result when the immune system reacts to otherwise harmless substances. One classification of allergic reactions is atopy, characterized by an immediate physiological response to an allergen. Examples of atopic disorders include asthma, rhinitis, and hayfever. A particular immunoglobulin, IgE, is excessively produced in atopy, which help bind the allergens to immune cells. This leads to the release of histamine from the immune cells, causing the irritating and sometimes deadly reactions such as blood vessel dilation and airway constriction.
In this study from the University of Nottingham, United Kingdom, 2,633 English adults (age 18 to 70) answered detailed dietary surveys from which their intake of vitamin E, vitamin C, magnesium, polyunsaturated fats, and other nutrients were determined. They also reported whether they suffered from asthma and hayfever. Most of the subjects (2,415) were then given skin allergy tests to grass pollen, cat fur, and a common species of skin mite, Dermatophagoides pteronyssinus. Blood tests of 2,498 subjects determined IgE levels. After adjusting for age, sex, and smoking, the researchers found a significant inverse association between dietary vitamin E intake and total IgE. The average daily vitamin E intake was 6.2 mg, and total Ige, 27.9 IU/mL. For every mg increase in vitamin E consumed, IgE was lowered by 5.2%, with the benefit maximizing at 7 mg vitamin E intake per day. Increased vitamin E intake also related to decreased incidence of hayfever, asthma, and airway hyper-responsiveness.
The authors conclude,"We believe that the effect of vitamin E on IgE and atopy, and the potential use of vitamin E in the primary and secondary prevention of allergic disease, justify closer investigation."
Fogarty, A. Lewis, S., Weiss, S., Britton, J. Dietary Vitamin E, IgE Concentrations, and Atopy. The Lancet. Vol. 356, pp.1573-, 2000.