Immune Health in Older Adults
By Mindy Hermann, MBA, RDN
Today’s Dietitian
Vol. 25 No. 3 P. 34

Today’s Dietitian explores the latest research on nutrition’s impact and products on the market claiming to help.

The late 2022 tripledemic of COVID-19, the flu, and respiratory syncytial virus magnified a health reality surrounding older adults. Men and women in their senior years can be highly susceptible to acute and chronic illnesses. According to the CDC, older adults are more likely to become seriously ill, with risk increasing when adults are in their 50s and in successive decades of life. The oldest adults, those 85 and older, are the most prone to contracting an infection or contagious illness and developing a chronic condition, such as CVD, type 2 diabetes, cancer, Alzheimer’s disease, or an autoimmune disease.

As a result, consumers’ interest in immune health is high. When market research firm Innova Market Insights1 surveyed consumers globally in 2022 about desirable functions in a food or beverage, more than one-third chose boosting immunity to viruses and colds. Consumers also reported that they purchased products to boost immunity more often than products with other benefits, like improving sleep, gut health, and hydration.

But can specific combinations of foods and supplements boost immunity and disease resistance in older adults? First, it’s important to understand the complexity of innate and adaptive immunity and how specific nutrients may help support immunity. In this article, Today’s Dietitian explores this question and the nutrients said to boost immune health as well as strategies for counseling clients.

Innate Immunity — The First Line of Defense
The innate immune system is the body’s first line of defense. Physical barriers to invaders, including the skin, nasal passages and sinuses, lining of the lungs, and intestinal mucosa, offer the first level of protection against pathogens. Several types of cells, namely macrophages, neutrophils, monocytes, and mast cells, enhance the body’s abilities to fight off pathogens through various mechanisms, including acute inflammation and the release of enzymes that destroy the offending organisms. The response of the innate immune system is immediate and not specific to the particular pathogen.

The body’s choreographed innate response to invaders begins at the cellular level. Macrophages emit chemical signals to attract neutrophils, or white blood cells. Neutrophils release reactive oxygen and nitrogen molecules, along with enzymes, cytokines, and other protein compounds, to destroy the invading pathogens, resolve the infection, and prevent long-term tissue damage. Neutrophil function and cytokine production are thought to decline with age, and neutrophils appear to become less able to travel to tissues that have been invaded by pathogens.

Adaptive Immunity Recognizes Previous Invaders
The lymph nodes are a key site of activity for the body’s adaptive immune system. Unlike innate immunity, adaptive immunity is invader-specific and can take up to several days to activate. The body produces antigens that interact with individual types of pathogens and signal T cells to begin their immune response. Adaptive immunity has a “memory” of which pathogens were encountered in the past. This enables the body’s active immune system to mobilize a faster response to previously known pathogens.

T lymphocytes (T cells), B lymphocytes (B cells), and dendritic cells in the lymph nodes are the warriors of adaptive immunity. T cells mature in the thymus gland and are the most common type of lymphocyte. Some T cells have regulatory functions, while others play a greater role in defending against pathogens and precancerous cells. B cells are generated by stem cells in the bone marrow. They’re essential fighters against bacterial infections and responders to vaccines, producing specific antibodies targeted to certain antigens. Dendritic cells serve as the interface between the innate and adaptive immune systems. Studies aren’t conclusive regarding the impact of aging on dendritic cell response. The number and types of T and B cells appear to decrease with age, as does immune response to vaccines. Moreover, T cells in older adults respond more slowly to previously unencountered pathogens, which is why flu outbreaks tend to be more severe among the elderly. Plus, infections tend to last longer and be more severe in older individuals.

Role of Food and Nutrition in Immunity During Aging
The relationship between nutrition and immune health is evolving. On a population level and in areas that have been identified as “Blue Zones,” diet characteristics such as smaller meals, greater intake of legumes and other plant-based whole protein sources, and limited animal protein intake are associated with longevity. In addition, several nutrients play an important role in the functioning of the immune system.

Vitamin C
Vitamin C has a long association with immune health, with numerous benefits to skin and other physical barriers, as well as both innate and adaptive immunity. As an antioxidant, vitamin C helps prevent damage to healthy cells from reactive oxygen species generated during the destruction of potential pathogens. It also supports the health of T and B cells. Although study results on vitamin C supplementation are inconsistent, they suggest a possible benefit in reducing the incidence and severity of respiratory illnesses in those with vitamin C deficiency and in older adults.2

Vitamin D
The active form of vitamin D, 1,25(OH)2D3, has numerous roles in innate and adaptive immunity, including production of antimicrobial and antiviral peptides in mucous membranes, inhibition of proinflammatory cytokines, and stimulation of certain types of T cells.3 During the peak of the COVID-19 pandemic, studies observed that individuals who were deficient in vitamin D were more likely to contract a severe case of COVID-19.4 In addition, mortality rates were higher among those with a vitamin D deficiency. Vitamin D supplementation hasn’t yet been shown to have a consistent benefit against COVID-19.5 However, study results suggest that vitamin D may help protect high-risk individuals, such as older adults, against severe symptoms associated with respiratory diseases.2

Vitamin E
Cells in the immune system contain high levels of the fat-soluble antioxidant vitamin E. A 2018 review summarizes the numerous immunity-related functions of vitamin E, including reducing inflammation, protecting fats in cell membranes from oxidation, and regulating production of reactive forms of oxygen and nitrogen.6 Vitamin E also is associated with the health of innate (macrophages, dendritic cells) and adaptive (T cells, B cells, natural killer cells) components of the immune system. The best food sources of vitamin E are almonds, seeds, vegetable oils, and leafy greens. A review article on nutrition, immunosenescence, and infectious disease notes that the effects of vitamin E supplementation on immune function and disease prevention in older adults are promising but inconsistent.2

The mineral zinc is highly active in immune health, with antiinflammatory, antiviral, antifungal, and immune cell signaling functions. In zinc deficiency, T cell and B cell numbers drop, and innate immunity also is affected. Individuals become more susceptible to infectious diseases, including pneumonia. The immune response in older adults, who are more likely to be deficient in zinc, improves with zinc supplementation.

The gastrointestinal tract is a key player in the body’s innate immune system. The gastrointestinal mucosa creates a physical barrier that prevents pathogens from passing from the gut into the bloodstream. Its barrier function is aided by the actions of beneficial gut microbes that naturally colonize the gut, along with probiotics that can be introduced via food, beverages, and supplements. The health of the gut microbiome diminishes with age.

Probiotics are defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP) as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” Immunity-related activities of beneficial cultures in the gut include immune modulation, lowering of gut pH to levels that prevent pathogens from colonizing in the gut and interacting with cytokines. The ISAPP notes that the action of microbes is determined by their genus, species, and strain—not all lactobacilli, bifidobacteria, and/or streptococci, for example, are probiotics with defined benefits to gut health.

Studies suggest that probiotics—alone or in combination with prebiotic fibers—may benefit immunity in older adults by boosting immune cell proliferation and activity, improving response to the influenza vaccine, decreasing inflammation, and reducing the incidence of respiratory and other infectious diseases.2

Immunity Promises on Products
Even though the COVID-19 pandemic increased consumer awareness regarding immunity and desire for products that boost immune health, direct claims regarding food/beverages/nutrients and immunity aren’t on the list of FDA-authorized or qualified health claims. This hasn’t prevented manufacturers, particularly of supplements, from mentioning immunity or immune support on package labels and in product positioning. According to a report by Future Market Insights, the global immune health supplements market size is expected to show compound annual growth of 10.2% between 2022 and 2032, with the United States accounting for a high percentage of immune health supplements sold globally.6 The rapid growth of immune health supplements during the pandemic years is likely to slow down somewhat, but top immunity ingredients such as vitamins C and D, and zinc, along with elderberry and echinacea, may continue to grow.8 It’s important to note that studies on elderberry and echinacea in older adults are limited in number.

A 2022 study analyzing dietary supplements marketed for immune health demonstrated reason for caution.8 Of 30 dietary immune health supplements purchased from, none had a third-party certification seal from NSF International or another recognized credentialing organization, 13 were misbranded, and nine had undeclared ingredients. One-half of the products displayed scientific sounding claims such as research based, research supported, scientifically proven, or backed by science without listing citations. The most frequent ingredients were echinacea, elderberry, vitamin C, vitamin D, and zinc.9

Foods, beverages, and supplements with immune health claims maintained a solid presence globally in the year ending June 2022, according to the Innova Market Insights database of new product launches.10 The stable number of launches demonstrates continued manufacturer and consumer interest in immune health after a big rise in introductions between the beginning of the pandemic in 2020 and midpandemic in 2021. According to the database, supplements account for more than one-half of global launches with an immune health claim—and a solid majority of immunity launches in the United States—while soft drinks and dairy are fastest growing. Few introductions are targeted specifically toward older adults.

Making Sense of Immune Health Claims
Clients should work together with dietitians who can help them improve their diet to support immune health, as well as sort through the various immunity claims on products. “As difficult as it is, help clients and patients to resist the urge to buy something the instant it catches their eye,” advises Lindsay Malone, MS, RD, CSO, LD, director of nutrition for practical healing and an adjunct professor of nutrition at Case Western Reserve University in Cleveland, Ohio. “When shopping for supplements, look for products that have been third-party tested, meaning that they were tested by a company or organization, like USP or, that doesn’t also make supplements. Moreover, check out product websites for claims, and make sure that any health-related claims are supported by peer-reviewed studies.” Malone says that the best types of studies are done by a third party rather than by the manufacturer, and are blinded, meaning the participants didn’t know if they were part of the treatment group or the control group. She recommends the Natural Medicines Comprehensive Database for research and other information on particular nutrients, herbs, and supplements.

“In my professional opinion, a diet that supports immunity should focus on two categories: what to eat and what to avoid,” Malone says. “Foods to include are those that are high in vitamin C, zinc, and vitamin D, as well as foods that support gut health, like high fiber and fermented foods.” Malone reminds clients to stay hydrated to help maintain the integrity of the mucosal lining of airways. Foods that cause spikes in blood glucose, including vitamin C–rich 100% juice, are at the top of Malone’s list of foods to avoid. Malone cautions that very few supplements are applicable to all older adults. Vitamin D is the exception since many older adults are deficient and food sources are limited.

Despite the appeal of food, beverages, and supplements with immune health claims, a healthful, balanced diet and lifestyle continue to be the best measures for a strong immune system for all ages.

— Mindy Hermann, MBA, RDN, is a food and nutrition communications consultant based in metro New York and a consultant to Innova Market Insights in Arnhem, Netherlands.

1. Innova Market Insights. Health and Nutrition Survey 2022.

2. Calder PC, Ortega EF, Meydani SN, et al. Nutrition, immunosenescence, and infectious disease: an overview of the scientific evidence on micronutrients and on modulation of the gut microbiota. Adv Nutr. 2022;13(5):S1-S26.

3. Durrant LR, Bucca G, Hesketh A, et al. Vitamins D2 and D3 have overlapping but different effects on the human immune system revealed through analysis of the blood transcriptome. Front Immunol. 2022;13:790444.

4. Carpagnano GE, Di Lecce V, Quaranta VN, et al. Vitamin D deficiency as a predictor of poor prognosis in patients with acute respiratory failure due to COVID-19. J Endocrinol Invest. 2021;44(4):765-771.

5. Rawat D, Roy A, Maitra S, Shankar V, Khanna P, Baidya DK. Vitamin D supplementation and COVID-19 treatment: a systematic review and meta-analysis. Diabetes Metab Syndr. 2021;15(4):102189.

6. Lee GA, Han SM. The role of vitamin E in immunity. Nutrients. 2018;10(11):1614.

7. Immune Health Supplements Market Outlook (2022–2032). Future Market Insights website. Published September 2022.

8. Krawiec S. The immune health category comes back down to earth: 2022 ingredient trends for food, drinks, and dietary supplements. Nutritional Outlook website. Published February 7, 2022.

9. Crawford C, Avula B, Lindsey AT, et al. Analysis of select dietary supplement products marketed to support or boost the immune system. JAMA Netw Open. 2022;5(8):e2226040.

10. Innova Market Insights product database. Innova Market Insights website.