Many older adults do not get enough zinc, vitamin C and vitamin D, and this can be related to decreased ability to fight infection. The purpose of this research study is to determine if taking a multivitamin/mineral supplement every day for 12 weeks will increase the ability of immune cells in blood to kill bacteria.

Vitamins C and D and the mineral zinc are each considered immune modulating micronutrients, but their specific effects on the immune system, especially when used in combination, is relatively unknown. Deficiency in each of these micronutrients is frequently observed in aging adults and may contribute to age-related declines in immune status. Based on prior published studies, the investigators hypothesize that supplementation of older adults with a combination of vitamin C, vitamin D, and zinc will increase the innate ability of neutrophils to kill invading bacteria through a variety of mechanisms, including increased phagocytosis, antimicrobial peptide expression and changes in reactive oxygen species (ROS) production.

Therefore, this study is designed to investigate the effects of Redoxon VI, a supplement consisting of a combination of vitamin C, vitamin D, and zinc on functional markers of the immune system of healthy, older adults when compared to a matched placebo. To accomplish this, the investigators will recruit 40 healthy adults between the ages of 60 and 75 and randomize them to either Redoxon VI or an identical, inactive placebo control supplement to be taken twice a day for 12 weeks.

Since neutrophil-mediated killing is a crucial defense against Staphylococcus aureus infection that declines with age, it will serve as a primary outcome in this study. Using blood collected from individuals before and after supplementation, the investigators will measure the ability of neutrophils to clear S. aureus cells, and compare the killing activity in those individuals receiving the vitamin and mineral supplement to those receiving the placebo. The investigators will confirm these changes in immune cell function by also measuring phagocytic activity in neutrophils, as well as their ability to produce ROS.

As secondary measures of immune function, the investigators will also determine circulating levels of neutrophils, monocytes and lymphocytes, measure cathelicidin antimicrobial peptide (also known as hCAP18/LL-37) levels, and determine changes in circulating levels of inflammatory cytokines.

Based on previous studies, the investigators expect that any increase in functional immune status will correspond to changes in vitamins C, D and zinc status in these individuals. The investigators expect the results from this study to provide the foundation for future studies investigating combinations of supplements on immune function and more extensive studies using these micronutrients to restore declines in immune function observed in older adults.

Inclusion Criteria:

• Serum vitamin D level 25-50 nmol/L (10-20 ng/ml), inclusive
• Willing to limit intake of salmon, herring and sardines to one 4-ounce serving per week for 3 weeks prior to and throughout the study.
• Willing to limit intake of oysters, shellfish, liver, beef, lamb and poultry dark meat to one 4-ounce serving per week for 3 weeks prior to and throughout the study.
• Willing to limit intake of citrus fruits and citrus fruit juices to 2 servings per day during the study for 3 weeks prior to and throughout the study.
• Willing to stop taking multivitamins, supplements containing zinc, vitamins C and D, and food/beverage products supplemented with zinc and vitamins C and D for 3 weeks prior to and throughout the study.

Exclusion Criteria:

• Usual dietary intake of zinc >15 mg/day (as determined in Telephone Screening Script)

• Tobacco use, including e-cigarettes, or smoking of any substance (e.g. cannabis) in the past three months or plans to smoke during the study.

• Have undergone a surgical procedure within the past two months or expect a surgical procedure in the next four months.

• Regularly consume more than two alcoholic drinks a day.

• Have participated in another clinical study within the past two months.

• Undergoing UV therapy (e.g. treatment for skin conditions such as psoriasis) or UV tanning.

• Have a significant acute or chronic illness such as cardiovascular disease, kidney or liver disease, diabetes, thyroid or parathyroid disorder, history of cancer less than five years.

• Have had bariatric surgery (e.g. gastric bypass, gastric banding, sleeve gastrectomy, etc.), other gastrointestinal procedure (e.g. cholecystectomy) or disorders (e.g. Crohn's disease, celiac disease, ulcerative colitis)

• Stage II hypertension (either systolic blood pressure > 159 mm Hg or diastolic blood pressure > 99 mm Hg)

• BMI < 18.5 or > 29.9

• Diagnosis of hypervitaminosis A, hypervitaminosis D, or hypercalcemia

• Have received an organ or tissue transplant

• Have eczema, atopic dermatitis, or psoriasis

• Have or have had allergy to medications or foods, seasonal allergies or allergic asthma after age 18 (childhood asthma/allergies not exclusionary)

• Diagnosis of an autoimmune disorder (e.g. lupus, rheumatoid arthritis, multiple sclerosis, etc.) or HIV positive status.

• Currently taking or using any of the following medications:

  • Topical medications containing retinoids
  • Desferioxamine
  • Disulfiram
  • Warfarin
  • Vitamin D analogs
  • Vitamin A analogs
  • Cholestyramine
  • Orlistat
  • Mineral oil (oral intake)
  • Thiazide diuretics
  • Calcium channel blockers
  • Phenobarbital or phenytoin or other anticonvulsants
  • Estrogen replacement therapy
  • Leukotriene receptor antagonists
  • Immunosuppressant/anti-rejection drugs
  • Oral corticosteroids