The Effect of Combinatorial Nutritional Supplementation on Immune Function in Healthy 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, histor…