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Am Fam Physician. 2004;70(3):594

Immune function declines with age. Some studies have suggested that nutritional supplementation can enhance immune responsiveness. Langkamp-Henken and colleagues conducted a study to determine if nutritional supplementation in healthy older persons could reduce the number of days of symptoms of upper respiratory tract infections (URTIs) during the cold and influenza season.

This prospective study enrolled ambulatory patients 65 years and older. Baseline nonfasting blood samples were collected; analysis included vitamin E concentrations, clinical chemistries, hematology, lymphocyte proliferation, and antibody titers to influenza vaccine components. Patients were randomized to receive control or experimental formula. The latter consisted of protein, anti-oxidants, selenium, zinc, fructo-oligosaccharides, and structured triacylglycerol. Both groups received some minimal vitamin supplementation and maintained normal diets. Participants were monitored for URTI symptoms and, at the end of the second week of the trial, were vaccinated against influenza. Blood samples were collected postvaccination and at the conclusion of the study.

The primary outcome variable was the number of days with URTI symptoms. Secondary variables included antibody response and lymphocyte proliferation to influenza vaccine components at baseline and final study time. Adverse effects were monitored, as were vitamin E concentrations.

Of the 66 subjects enrolled, 18 control-formula patients and 16 experimental-formula patients completed the 183-day trial. The median number of days with cold and influenza symptoms per control-formula and experimental-formula patients were three, and zero, respectively. Of those completing the study, 13 of 18 control-formula patients reported a total of 156 days of symptoms, compared with six of 16 experimental-formula patients who recorded a total of 78 days of symptoms.

In general, antibody titers were not different between groups at any blood draw. However, the rate of rise for the A/Beijing vaccine component showed that a greater percentage of experimental-formula completers than control completers had fourfold antibody titer increases at postvaccination time. Lymphocyte proliferation was significantly greater in the experimental group than in the control group at the postvaccination blood draw but not at baseline or in the final blood draw.

The authors conclude that a nutrient formula known to enhance immune function could reduce the number of days of URTI symptoms during the cold and influenza season. Postvaccination antibody titers to A/Beijing and lymphocyte proliferation were higher in the experimental group than in the control group. Given that the elderly are a heterogeneous group, different micronutrients may have been protective in different persons. Micronutrient supplementation in the form of pills or formula may result in clinically measurable URTI and influenza protection in an older population, in whom influenza vaccine protects against hospitalization in only 30 to 70 percent of those vaccinated.

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Copyright © 2004 by the American Academy of Family Physicians.

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