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Dietary Supplements vs. Functional Foods: Safety and Labeling

Updated: Jun 11

A year into the COVID-19 pandemic, consumer interest is on the rise for dietary supplement and functional food products that improve overall health. The global dietary supplements market size was valued at $48.22 billion in 2019 and is projected to reach $117.92 billion by 2027 (Fortune Business Insights, 2020), while the functional food market size was valued at $177.77 billion and is projected to reach $267.92 billion during the same time period (Allied Market Research, 2020). With an increase in sales have come questions on how dietary supplements and functional foods are different. The major differences in these products are the FDA safety and labeling requirements, discussed below.

Definitions and Examples

The Food and Drug Administration (FDA) safety and labeling requirements is dependent upon whether the product is classified as a “food” or a “dietary supplement.” FDA’s Federal Food, Drug, and Cosmetic Act (FFDCA) defines “food” as “articles used for food or drink for man or other animals, chewing gum, and articles used for components of any such article” (FFDCA Sec. 201(f)). Furthermore, “conventional foods” are those that are consumed primarily for taste, aroma, and nutritive value (FDA, 2014). There is not a legal definition for “functional foods”; However, there is a general consensus that a functional food is a conventional food that contains some health-promoting component(s) beyond traditional nutrients; that is, substances having caloric value (i.e., proteins, carbohydrates and fats) or, vitamins and minerals (Onel, 2001; Litwin et al., 2018). 

Many functional foods get their health promoting properties from naturally occurring compounds that have no accepted nutritional value called phytochemicals. For example, a vitamin is a food substance essential for life, whereas a beneficial phytochemical is a substance in plants that may affect health, but is not essential for life (Insel et al., 2016). A case in point is the phytochemicals in tomatoes, carotenoids (e.g., lycopene, beta-carotene) which are said to have anti-inflammatory properties that have been associated with improving cardiovascular health. More examples of phytochemicals found in a variety of plant sources are provided in Table 1.

Table 1. Examples of phytochemicals (adapted from Insel et al., 2016)

Class/ Bioactive Food Components

Food Sources

Potential Benefit



Carrots, pumpkin, sweet potato, cantaloupe.

Neutralizes free radicals that may damage cells; bolsters cellular antioxidants defenses; can be made into vitamin A in the body.



Cranberries, cocoa, apples, strawberries, grapes, wine, peanuts, cinnamon.

May contribute to maintenance of urinary tract health and heart health.

Phenolic acids

Caffeic acid, ferulic acid

Apples, pears, citrus fruits, some vegetables, coffee.

May bolster cellular antioxidant defenses; may contribute to maintenance of healthy vision and heart health.



Cauliflowers, broccoli, broccoli sprouts, cabbage, kale, horseradish.

May enhance detoxification of undesirable compounds; bolster cellular antioxidant defenses.


Inulin, fructo-oligosaccharides, polydextrose

Whole grains, onions, garlic, honey, leeks

May improve gastrointestinal health; may improve calcium absorption.

Also, a functional food product can be created by modifying traditional food by agricultural, enzymatic, chemical, or technological means (Litwin et al., 2018). An example of this is orange juice with extra pulp that helps maintain gastro-intestinal health by increasing fiber consumption and promoting growth of beneficial bacteria in the colon. Overall, foods are considered functional if they contain non-nutritive beneficial ingredients. From a regulatory standpoint, functional food products fall into the category defined above as “food.” In contrast, a dietary supplement has a legal definition. The following is a condensed definition of a “dietary supplement” in the FFDCA: “The term ‘‘dietary supplement’’— (1) means a product (other than tobacco) intended to supplement the diet that bears or contains one or more of the following dietary ingredients: (A) a vitamin; (B) a mineral; (C) an herb or other botanical; (D) an amino acid; (E) a dietary substance for use by man to supplement the diet by increasing the total dietary intake; or (F) a concentrate, metabolite, constituent, extract, or combination of any ingredient described in clause (A), (B), (C), (D), or (E); (2) means a product that— …(B) is not represented for use as a conventional food or as a sole item of a meal or the diet; and (C) is labeled as a dietary supplement…” (FFDCA Sec. 201(ff)). Unlike functional foods, dietary supplements cannot be represented for use as a conventional food or as a sole item of a meal or the diet and are not used primarily for their taste or aroma. Furthermore, dietary supplements were originally restricted (according to the Dietary Supplement Health and Education Act) to delivery formats such as a capsule, powder, softgel, gelcap, tablet, or liquid (FFDCA Sec. 411(c)(1)(B)(i)), so they would not be mistaken for a meal. Later, FDA relaxed the rules a bit (as it can under the Chevron decision) to allow delivery in other forms including a bar (e.g., snack bar) or bottled liquid (e.g., “vitamin waters”), but if a supplement is delivered in this manner, information on the label must not represent the product as a conventional food or a sole item of a meal or diet, and have the “Supplement Facts” label (FDA, 2019b). In the past, companies have made the mistake of marketing a product as a dietary supplement that represents a conventional food. For example, in an FDA warning letter to an energy drink company, the FDA stated that the coffee product is represented for use as a conventional food, even though the product used the term “energy supplement” on the label and used “Supplement Facts” panel for nutrition labeling. The factors which determined that the coffee product is represented as a conventional food and not a dietary supplement included the following (FDA, 2012): • Coffee is a beverage and a conventional food. • The label states “Enjoy this fully refreshing beverage super chilled.” • The product is similar to a typical canned beverage in packaging and appearance. Both functional foods and dietary supplements may include ingredients such as vitamins, minerals, herbs, amino acids, and enzymes. For instance, anthocyanin from cranberries is a dietary supplement when presented in a capsule. Anthocyanin is also present in cranberry juice, but because the anthocyanin has no established nutritive value, anthocyanin makes cranberry juice a functional food.


Functional ingredients added to foods to make them “functional foods” must be approved as a food ingredient. Therefore, a functional food ingredient is a food additive that is subject to premarket approval by the FDA, unless the ingredient is “Generally Recognized As Safe” (GRAS) by qualified experts under the conditions of the intended use. As such, if a company adds an ingredient that provides a benefit beyond basic nutrition to create a functional food, the company is responsible for determining that the ingredient meets the GRAS standard or is approved by the FDA as a food additive (GAO, 2000). Use of an ingredient that is not compliant with the FFDCA (i.e., GRAS or an approved food additive) is an unapproved food additive and the food to which it has been added is adulterated and subject to seizure. As a non-safety footnote, can ingredients be added to food willy-nilly? NO! The regulation 21 CFR §170.230 requires an acceptable technical effect for substances added to food (out of those listed in 21 CFR §170.3(o)), but FDA has not been too emphatic that a technical effect be identified. FDA regulates dietary supplements under a different set of regulations than those covering conventional foods. Under the Dietary Supplement Health and Education Act (DSHEA) of 1994, manufacturers and distributors of dietary supplements and dietary ingredients are responsible for evaluating the safety and labeling of their products before marketing their products (FDA, 2019a). For a “new dietary ingredient” (NDI) (defined as a dietary ingredient that was not marketed in the U.S. before October 15, 1994), an NDI notification must be submitted 75 days before introducing the dietary supplement into interstate commerce. The company must have a basis for concluding that a supplement containing a new dietary ingredient will reasonably be expected to be safe when used under the condition recommended or suggested in the labeling (21 U.S.C. §350b(a)). As opposed to a food ingredient, which must have a reasonable certainty of no harm, which must be determined by experts, who by virtue of their training and experience, can make such a decision as to whether a substance is safe or not, according to its intended use. In summary, dietary supplement ingredients could be used in dietary supplements without being either approved food additives or generally recognized as safe (GRAS) ingredients, unlike functional food ingredients, because food ingredients are held to a higher standard of safety than are dietary supplements. In general, FDA’s role with a dietary supplement product happens after it reaches market. At that point, the FDA is responsible for taking action against any adulterated or misbranded dietary supplements (FDA, 2019a).

Labeling Claims

Both functional food ingredients and dietary supplement ingredients can contain ingredients that reduce of the risk of disease or health related condition; or have an impact on normal structure or function of the human body. On the label, any statement that characterize the relationship between a substance and a disease or health-related condition is called a health claim (21 CFR §101.14). For example, oatmeal with the appropriate amount of beta-glucan fiber can highlight its benefits in reducing the risk of heart disease (Insel et al., 2016). Health claims are subject to premarket review and authorization by FDA for both dietary supplements and functional foods (FDA, 2018).

A statement that addresses the role of a specific substance in maintaining normal healthy structures (such as the skeletal system) or functions (such as maintenance of a healthy urinary tract) of the body is considered to be structure/ function claim (GAO, 2000; FDA, 2018). Unlike health claims, structure/ function claims are not subject to premarket review and authorization by FDA (FDA, 2018). Importantly, a structure/ function claim on a conventional or functional food must be based on the food’s nutritive value. An example of this is orange juice with added vitamin C, vitamin E, and zinc to “support your natural defenses” (Insel et al., 2016). Since phytochemicals (Table 1) do not have nutritive value, functional foods would not be allowed use phytochemicals in structure/ function claims.

On the other hand, a dietary supplement, can make a structure/ function claim that does not focus on the nutritive effects (Table 2). For example, as a dietary supplement, anthocyanidin in a capsule form can advertise maintenance of a healthy urinary tract. As a food, cranberry juice can advertise maintenance of a healthy urinary tract because it has nutritive value (such as carbohydrates), but not the anthocyanidin which does not have nutritive value.

Unlike dietary supplements, functional foods that make structure/ function claims are not required to notify FDA of these claims (Table 2). For dietary supplements, the following list defines structure/ function claims that require FDA notification (FDA, 2018): 1. Describe the role of a nutrient or dietary ingredient intended to affect the normal structure or function of the human body, for example, “calcium builds strong bones”; 2. Characterize the mechanism by which a nutrient or dietary ingredient acts to maintain such structure or function, for example, “fiber maintains bowel regularity,” or “antioxidants maintain cell integrity”; and 3. General well-being claims describe general well-being from consumption of a nutrient or dietary ingredient, for example, “taking vitamin C will help you feel healthy.”

Structure/ function claims that describe a benefit related to a nutrient deficiency disease (like vitamin C and scurvy), do not require FDA notification if they also say how widespread such a disease is in the United States (FDA, 2018). For the three types of structure/ function claims that require FDA notification, the manufacturer must have substantiation that the claim is truthful and not misleading. Then, in no later than 30 days after marketing the dietary supplement with the claim, the manufacturer must submit a notification with the text of the claim to FDA. If a dietary supplement label includes such a claim, it must state in a “disclaimer” that FDA has not evaluated the claim. The disclaimer must also state that the dietary supplement product is not intended to “diagnose, treat, cure or prevent any disease,” because only a drug can legally make such a claim (FDA, 2018). According to the United States General Accounting Office (GAO), “this disclaimer requirement does not exist for functional foods that carry structure/ function claims, even if the same ingredient is the basis of the label claim” (GAO, 2000). For example, a dietary supplement has a disclaimer on its label for a structure/ function claim related to maintaining a healthy circulatory system, but a functional food containing the same ingredient and claim does not require the disclaimer (GAO, 2000).

Table 2. Structure/ function claims requirements for functional foods and dietary supplements (GAO, 2000; FDA, 2018)

Structure/ function claims-related requirements

Functional foods

Dietary supplements

Structure/ function claims cannot be false or misleading.



Substance on which the structure/ function claim is based, must have nutritive value.


Not Required

Must notify FDA within 30 days after marketing a product that bears a structure/ function claim.

Not Required


Must include a disclaimer on product labels that contain structure/ function claims that states the claim has not been evaluated by FDA.

Not Required



The Venn Diagram below summarizes the key differences between functional foods and dietary supplements discussed in the article. The benefits of marketing a product as a dietary supplement in comparison to functional foods include (1) ingredients can be used in dietary supplements without being either approved food additives or generally recognized as safe (GRAS) ingredients; and (2) dietary supplements can make structure/ function claims without the focus on nutritive value. However, unlike dietary supplements, functional foods can make structure/ function claims without notifying the FDA of these claims or providing a disclaimer statement on these products. Burdock Group can help companies determine the best regulatory pathway to get their product to market, as well as review the label of their product to ensure that it meets FDA requirements. 


Allied Market Research (2020) Functional Food Market to Reach $267.92 Bn, Globally, by 2027 at 6.7% CAGR. (site visited on March 31, 2021).

FDA (2012) WARNING LETTER NO. 2012-NOL-22.

FDA (2014) Guidance for Industry Distinguishing Liquid Dietary Supplements from Beverages.

FDA (2018) Label Claims for Conventional Foods and Dietary Supplements | FDA. (site visited on April 12, 2021).

FDA (2019a) Dietary Supplements. (site visited on April 5, 2021).

FDA (2019b) Questions and Answers on Dietary Supplements. (site visited on April 5, 2021).

Fortune Business Insights (2020) Dietary Supplements Market Size, Growth | Industry Trends [2020-2027]. (site visited on March 31, 2021).

GAO (2000) Food Safety: Improvements Needed in Overseeing the Safety of Dietary Supplements and “Functional Foods” (Letter Report, 07/11/2000, GAO/RCED-00-156).

Insel, P.; Ross, D.; Mcmahon, K. and Bernstein, M. (2016) Discovering Nutrition. 5th Edition. In Spotlight On Dietary Supplements And Functional Foods. Jones & Barlett Learning, LLC, Burlington, MA p. 277–304.

Litwin, N.; Clifford, J. and Johnson, S. (2018) Functional Foods for Health. Colorado State University Extension. Food and Nutrition Series| Health. Fact Sheet No. 9.324.

Onel, S. (2001) Functional Foods, Nutraceuticals, Designer Foods. Regulatory Affairs Focus. 14–18.

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