Explore trends in consumer behavior, functional foods and supplements since the start of the COVID-19 pandemic.
The human immune system consists of two major components: the innate and acquired immune systems. A person is born with an innate immune system as their first line of defense. This includes factors such as skin integrity, mucosal membranes and immune cells including natural killer cells, or NK. The acquired immune system, also called the adaptive immune system, includes T- and B-cells, which help the body develop an immune “memory” when exposed to viruses or immunizations.
Individual nutrient intake, including some vitamins and minerals, can affect the immune system by supporting healthy physical barriers in the skin and mucosal membranes, or by impacting the gut microbiome, innate immune system macrophage function (white blood cells that kill microorganisms) and adaptive immunity via T- and B-cell function. Certain nutrient inadequacies may impair the immune response, and micronutrients including vitamins A, C, D, E, B6, B12 and folate and the minerals iron and zinc influence all aspects of the immune system.
Data from the 2005–2016 National Health and Nutrition Examination Surveys revealed many Americans who are 19 or older may have usual intakes below the estimated average requirement of vitamins A, C, D and E, as well as zinc, from foods. Information from the National Institutes of Health’s Office of Dietary Supplements indicates that while nutrients including vitamins C, D and E and minerals such as zinc do help support immune function, the primary goal should be to prevent deficiency rather than taking more than the recommended amounts.
Nutrients, the Immune System and COVID-19
There is some evidence that the immune system is influenced by nutritional status and that malnutrition does increase risk of admission to the intensive care unit and mortality from COVID-19. However, less is known about the potential preventative benefits of individual nutrients on viral infections, including COVID-19. Developed by a panel of experts, the NIH’s report on treatment guidelines for COVID-19 includes information about zinc and vitamins C and D as adjunctive therapies, but much of that data is based on supplements rather than functional foods. The guidelines for vitamins C and D state that there is currently not enough data to recommend for or against their use in preventing or treating COVID-19. In the case of zinc, the data is lacking for or against its use as a treatment; however, the panel recommends against its use as a supplement in amounts above the recommended dietary allowance in the prevention of COVID-19, unless it is being administered during a clinical trial. A scoping review by the Academy’s Evidence Analysis Center found a lack of evidence regarding the efficacy of additional micronutrients or conditional amino acids such as glutamine or arginine in reducing the severity of disease in people infected with COVID-19.
Currently, there are no specific nutritional guidelines for those who have or are at risk for COVID-19. Medical nutrition therapy guidelines say registered dietitian nutritionists should provide care for those infected with COVID-19 to help optimize nutritional status and prevent malnutrition including screening for food insecurity and helping provide budget-friendly food options, when appropriate.
Market Trends for Functional Foods and Immune Support
Consumer sales for functional foods with proclaimed “immune-supporting” ingredients such as vitamin C, vitamin D, elderberry, beta-glucan, probiotics and antioxidant polyphenols have increased greatly since the COVID-19 pandemic began in 2020. This trend led to increased product claims — some illegal — such as statements about disease treatment.
Projections suggest global immunity-focused functional foods will grow by $170 billion between 2019 and 2023, reaching $1 trillion. Market research studies show that consumers are especially interested in foods rich in vitamins C and D, specifically due to fears of COVID-19.
A 2020 consumer market report revealed that 31 percent of consumers are taking more supplements as a result of the pandemic and 29 percent are consuming more functional foods and beverages, including fortified or enriched products, and increasing consumption of healthful foods such as whole grains, fruits, vegetables, plain bottled water and fruit or vegetable juices. When asked why they were increasing use of supplements and functional foods, their reasons included immunity, increased energy, general illness prevention and for digestion and microbiome support.
Regulatory Policies and Oversight
A study examining the term “immune boosting” on Instagram during the COVID-19 pandemic found that between April 15 and May 15, 2020, the use of the hashtag #immunebooster increased more than 46 percent. Researchers warn that, given the lack of evidence that specific products can enhance the immune system for protection against COVID-19, using these types of terms can be misleading to consumers.
The U.S. Food and Drug Administration and Federal Trade Commission have been addressing product label claims as they relate to the immune system and specific diseases such as COVID-19. Companies are not allowed to claim their product prevents, treats or alleviates signs or symptoms of COVID-19. Additional guidance provided by industry experts includes that companies should not make anti-inflammatory or anti-viral claims. This advice extends to social media, blogs, websites and product representatives or influencers.
Additionally, these experts advise companies and individuals to use caution with terms such as “boost,” “build,” “defend,” “therapeutic” or “protect” in regard to the immune system, and instead can claim immune or general health support. Further advice includes taking caution with using the hashtags #coronavirus or #COVID19 when referencing a product or health claim.
Potential Dangers of Supplemental Functional Foods
Many foods are functional in that they provide energy, protein or other nutrients to the body. Although there is no specific legal definition in the U.S., working definitions for functional foods have been used in the past by several organizations, including the Academy of Nutrition and Dietetics. According to the “Position of the Academy of Nutrition and Dietetics: Functional Foods,” published in 2013 and now retired, “the term functional foods is defined as whole foods along with fortified, enriched, or enhanced foods that have a potentially beneficial effect on health when consumed as part of a varied diet on a regular basis at effective levels based on significant standards of evidence.” Because many functional foods are fortified or enriched with nutrients beyond the recommended amounts, there is a risk of consuming more than the Dietary Reference Intakes of many nutrients, which could be problematic. For example, people who exceed the Tolerable Upper Intake Level for vitamin E (1,000 milligrams per day for adults) may experience an increased risk of bleeding or hemorrhagic stroke. Supplementing can be problematic as well. For instance, vitamin E supplements can interact with medications including anticoagulants and statins. Chronic intakes of supplemental zinc in high amounts can impair copper absorption, alter iron function and even reduce immune function — the opposite effect desired by many people taking additional zinc.
Types of claims that may appear on food and supplement labels, as permitted for use by the FDA:
- Nutrient content
- Authorized health
- Qualified health
Nutrient content claims relate to the amount that is declared based on established criteria. For example, the FDA regulates terms used in nutrient content claims, including antioxidant claims, such as “high,” “good source” and “more.” For individual nutrients, the use of “high potency” can be used when an individual vitamin or mineral is at 100 percent or more of the Reference Daily Intake (per reference amount customarily consumed).
Structure/function claims focus on how a nutrient may influence the structure or function of the human body. On supplements, packaging will indicate, “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.” This is not required on conventional foods.
Authorized health claims are based on “significant scientific agreement” and address the relationship between a food or a food component and a health condition or a risk for it. Qualified health claims are supported by less evidence and must include a disclaimer stating such.
The FDA regulates claims that affect a disease, including if it protects against a disease or affects signs and symptoms. Further, the FDA regulatory guidance explains that implied disease claims, depending on the context, could include words such as “promote,” “regulate,” “stimulate,” “support,” “maintain” or “lower.” In these cases, the FDA warns that caution should be used with the words “diagnose,” “cure,” “treat” or “prevent,” since these terms are associated with disease claims and require FDA approval in the case of drug products or must follow guidance for health claims if used on foods.
Role of the RDN
Registered dietitian nutritionists should be mindful of language used in education materials, blogs, websites and social media posts, as well as know what can and can’t be said about potentially immune-protecting foods or nutrients. Use caution with phrases such as “immune boosting,” which studies suggest could be fueling the spread of misinformation and misleading consumers.
Patients or clients may ask RDNs questions about functional foods and products to support the immune system or general health during the COVID-19 pandemic and beyond. Aside from conducting a nutrition assessment for potential micronutrient deficiencies, RDNs can take a whole foods approach, explaining how to obtain nutrients from food and when supplements may be needed, as indicated in the “Position of the Academy of Nutrition and Dietetics: Micronutrient Supplementation.” This position paper guides nutrition professionals to stay abreast of research regarding the efficacy of supplements and to educate and guide consumers on the appropriate and safe use of micronutrient supplements.
Nutrition professionals can refer to the Academy’s “Guidance Regarding the Recommendation and Sale of Dietary Supplements” for more information about regulatory, legal and ethical considerations and the “Scope and Standards for the RDNs and NDTRs Collection” in the Journal of the Academy of Nutrition and Dietetics.
For patients or clients interested in ways to protect their immune response, RDNs can share evidence-based guidance on lifestyle factors including recommendations for sleep, exercise and alcohol consumption. Studies show a direct connection between sleep and immunity, protecting both immune system maintenance and response when sleep is achieved in adequate amounts.
Research on how regular (three to five days per week, 20- to 60-minute sessions), moderate-intensity exercise modulates immunity shows promise for benefiting several aspects of the immune response. For adults who are of legal age and choose to drink alcohol, the 2020-2025 Dietary Guidelines for Americans specify a limit of one drink or less in a day for women and two drinks or less in a day for men on days alcohol is consumed. This can be an important piece of guidance given evidence that chronic, heavy alcohol intake can reduce immunity to both viral and bacterial infections.
RDNs are well-positioned to educate consumers on all aspects of dietary and lifestyle factors that help achieve optimal immune function.
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