30 Jan Zinc Levels Can Be Improved In Nursing Home Patients with Supplementation
MedicalResearch.com Interview with:
Simin Nikbin Meydani, D.V.M., Ph.D.
Director, JM USDA-HNRCA at Tufts University
Professor of Nutrition and Immunology
Friedman School of Nutrition Science and Policy
and Sackler Graduate School at Tufts University
Boston, MA 02111
Medical Research: What is the background for this study?
Dr. Meydani: A significant number of older people are zinc deficient which can result in a compromised immune system which weakens as the body ages, making older adults more susceptible to infections and higher incidence and morbidity from pneumonia. Older adults with impaired immune response, particularly T cell-mediated function, have a higher susceptibility to infections and cancer. Our research team from the Jean Mayer USDA Human Nutrition Research Center on Aging created a small double-blind, placebo-controlled trial involved adults age 65 or older from three Boston-area nursing homes to determine the feasibility of increasing serum zinc concentrations in older adults. The full findings are published in The American Journal of Clinical Nutrition.
These results have a significant public health implication for the older adults because it shows directly that correction of a nutrient deficiency can improve immune response in older adult (a biological function which consistently has been shown to be impaired with aging).
Medical Research: What are the main findings?
- Zinc supplementation increased serum zinc concentrations in nursing home residents with low zinc levels.
- Zinc supplementation increased both the number and function of T cells.
- For those in the treatment group who were moderately zinc-sufficient at baseline, their serum zinc levels exceeded the cut-off standard for adequate serum zinc levels.
- Participants in the treatment group whose serum levels were measured as substantially zinc-deficient at baseline did not experience an increase to normal levels during the trial.
- The was a positive association between serum zinc level and T cell function and number
Medical Research: What should clinicians and patients take away from your report?
Dr. Meydani: Previous work we had done showed that 30 percent of nursing home residents have low serum zinc levels and those with low serum zinc levels had a significantly higher incidence of pneumonia and morbidity from it. Our new finding is that serum zinc levels can be improved in older adults with zinc supplementation and that this is associated with enhancement of T-cell numbers and function strongly suggests that ensuring adequate zinc consumption by older adults could have a significant impact on reducing the incidence of and morbidity from infection, which is a major public health problem in older adults.
The study participants had baseline serum levels of zinc that ranged from moderately to very zinc-deficient. Participants were given zinc supplements or a placebo for three months. A total of 25 people completed the study, with 13 receiving the placebo (a daily multi-vitamin with only 5 mg of zinc), and 12 receiving a daily multi-vitamin with 30 mg of zinc. A serum-level of 70 micrograms per deciliter was used as the cut-off standard for adequate serum zinc level and measuring improvement from supplementation. The function of the immune response was assessed by determining the T cell profile and function.
In addition to serum zinc concentrations, the researchers found that zinc supplementation improved the function of T-cells as determined by their ability to proliferate in response to stimuli that mimicked infection. Furthermore, they saw a positive correlation between serum zinc levels and the number and function of T-cells. This effect of zinc was attributed to increasing the number of T-cells rather than enhancing the function of each T-cell.
MedicalResearch: What populations are most vulnerable to zinc deficiency?
Dr. Meydani: Older adults with weakened immune systems, children, and those with digestive disorders have difficulty getting or absorbing enough zinc.
MedicalResearch: If taking a zinc supplement, what is the proper daily dosage for an older adult? And can too much be harmful?
Dr. Meydani: Supplementation with 30 mg/d zinc gluconate corrected zinc deficiency in a majority of subjects but in some cases with very low serum zinc levels, a higher level or a longer period of supplementation might be needed.
It should be noted that too much zinc (the upper limit for adults is 40 mg/day) can be harmful. Some researchers suspect, however, the older adults do not absorb or use zinc as efficiently as others. In addition, while serum zinc levels are a commonly used measure to evaluate zinc deficiency, they might not accurately reflect cellular zinc status. Some cells might exhibit low zinc levels, which impacts their function, even when serum zinc levels are normal.
Dr. Meydani: We need to better understand how much supplementation is needed for certain people, and for how long a period, so that more refined recommendations can be made.
We are hopeful in the future this research will result in more definitive studies of a larger size, longer duration, and with additional doses of zinc are needed to determine the impact of baseline serum zinc concentration, and genetic and gut microbiota on the optimal dose of zinc needed to maintain adequate zinc concentrations, improve the immune response as well as decrease in the incidence and duration of infectious diseases, such as pneumonia, in zinc deficient nursing home elderly. Findings from such studies may have significant impact for improving the health-span and quality of life in elderly as well as reducing the economic costs associated with their care.
MedicalResearch: Is there anything else you would like to add?
Dr. Meydani: While the study was done with nursing home residents, we know that zinc deficiency also exists in non-institutionalized older adults. On average, zinc supplementation measurably improved serum zinc levels in these older adults, with most participants achieving serum zinc levels considered to be adequate.
Effect of zinc supplementation on serum zinc concentration and T cell proliferation in nursing home elderly: a randomized, double-blind, placebo-controlled trialAm J Clin Nutr ajcn115188; First published online January 27, 2016.doi:10.3945/ajcn.115.115188