United States Court of Appeals

For the First Circuit

No. 22-1332

RICHARD FERRARI, individually and on behalf of all others 

similarly situated; WILLIAM BOHR, individually and on behalf of 

all others similarly situated,

Plaintiffs, Appellants,

v.

VITAMIN SHOPPE INDUSTRIES LLC f/k/a Vitamin Shoppe Inc.,

Defendant, Appellee.

APPEAL FROM THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF MASSACHUSETTS

[Hon. George A. O'Toole, Jr., U.S. District Judge]

Before

Montecalvo and Thompson, Circuit Judges,

and Carreño-Coll,

 District Judge.

Mark R. Sigmon, with whom Nick Suciu, III, Milberg Coleman 

Bryson Phillips Grossman PLLC, Charles J. LaDuca, Brendan S. 

Thompson, Cuneo Gilbert & LaDuca, LLP, Joseph J. Siprut, Erica C. 

Mirabella, Charles E. Schaffer, and Levin Sedran & Berman LLP were 

on brief, for appellants.

Michael R. McDonald, with whom Caroline E. Oks and Gibbons, 

P.C. were on brief, for appellee. 

 Of the District of Puerto Rico, sitting by designation.
June 9, 2023
- 3 -

CARREÑO-COLL, District Judge. Richard Ferrari and 

William Bohr purchased three dietary supplements with glutamine in 

the hope that the glutamine would -- as the labels said -- help 

their muscles grow and recover after intense exercise. When they 

did not see any results, they sued the products' manufacturer, 

Vitamin Shoppe, for several state torts. The district court 

granted summary judgment to Vitamin Shoppe, ruling that the 

plaintiffs' state law claims are preempted because the labels

comply with federal law. We affirm. 

I.

The Food, Drug, and Cosmetic Act ("FDCA") is designed to 

protect consumers from harmful products. Perham v. 

GlaxoSmithKline LLC (In re Zofran (Ondansetron) Prods. Liab. 

Litig.), 57 F.4th 327, 330 (1st Cir. 2023). Congress amended the 

FDCA through the Dietary Supplement Health and Education Act of 

1994 ("DSHEA") to establish a uniform framework to regulate dietary 

supplements. Pub. L. No. 103-417, 108 Stat. 4325, 4325–26 (1994). 

Under the FDCA and DSHEA, manufacturers may make so-called 

"structure/function claims" about dietary supplements. Kaufman

v. CVS Caremark Corp., 836 F.3d 88, 92 (1st Cir. 2016). A 

structure/function claim "describes the role of a nutrient or 

dietary ingredient intended to affect the structure or function in 

humans" or "characterizes the documented mechanism by which a 

nutrient or dietary ingredient acts to maintain such structure or 
- 4 -

function." 21 U.S.C. § 343(r)(6)(A). That a nutrient, for 

example, "helps promote digestion" or "supports the immune system" 

is a structure/function claim. Regulations on Statements Made for 

Dietary Supplements Concerning the Effect of the Product on the 

Structure or Function of the Body, 65 Fed. Reg. 1000, 1006, 1028–

29 (Jan. 6, 2000) (codified at 21 C.F.R. pt. 101). To make such 

a claim, the manufacturer must have "substantiation that [the 

claim] is truthful and not misleading." § 343(r)(6)(B). And the 

dietary supplement's label must bear a disclaimer stating that the 

claim has not been evaluated by the Food and Drug Administration 

("FDA") and that the "product is not intended to diagnose, treat, 

cure, or prevent any disease." § 343(r)(6)(C). Finally, the 

claim itself may not purport "to diagnose, mitigate, treat, cure, 

or prevent" disease. § 343(r)(6). 

If the manufacturer's label satisfies § 343(r)(6)'s 

requirements, consumers may not attack the structure/function 

claim under state law. See Kaufman, 836 F.3d at 91–92. To keep

labeling requirements uniform, the FDCA expressly preempts "any 

requirement" under state law "respecting any claim of the type 

described in section 343(r)(1) . . . made in the label or labeling 

of food that is not identical to the requirement of section 

343(r)." 21 U.S.C. § 343-1(a)(5). Structure/function claims 

under § 343(r)(6) fall within § 343(r)(1)'s ambit. See

§ 343(r)(6) (stating that, "[f]or purposes of paragraph (r)(1)(B), 
- 5 -

a statement for a dietary supplement may be made if" the statement 

complies with certain requirements). So they are "claim[s] of the 

type described in section 343(r)(1)." And they are claims made 

in the labeling of food because dietary supplements are "deemed"

food under the FDCA, except in limited circumstances that do not 

apply here. See 21 U.S.C. § 321(ff). Thus, the FDCA expressly 

preempts any state law that establishes labeling requirements for 

structure/function claims that are not identical to the 

requirements in § 343(r)(6). See Dachauer v. NBTY, Inc., 913 F.3d 

844, 847–48 (9th Cir. 2019). The "net effect" of this is that the 

manufacturer "prevail[s] if its label satisfies the requirements 

of [§ 343(r)(6)]." Kaufman, 836 F.3d at 92. 

With our statutory scaffolding in place, we turn to what 

happened below. The plaintiffs purchased three dietary 

supplements: Glutamine, Creatine & Glutamine with Beta-Alanine, 

and BCAA & Glutamine.1 Glutamine is a main ingredient in all three

of them. The Glutamine supplement states that glutamine "is 

involved in regulating protein synthesis and has been shown to 

possess [a]nti-[c]atabolic properties2 to help preserve muscle" 

and that "[i]ntense exercise can deplete glutamine stores, 

1 Ferrari purchased Creatine & Glutamine with Beta-Alanine, 

and Bohr purchased Glutamine and BCAA & Glutamine. We group the 

products together for analytical ease. 

2 An anti-catabolic substance reduces the breakdown of muscle 

proteins. 
- 6 -

however, supplemental glutamine is thought to replenish these 

stores allowing for enhanced recovery." The Creatine & Glutamine 

with Beta-Alanine supplement says that "[g]lutamine helps support 

muscle growth and recovery as well as immune health."3 And the 

BCAA & Glutamine supplement states that glutamine has "anticatabolic properties." The plaintiffs claimed that these 

statements are false and misleading under state law. 

Vitamin Shoppe moved for summary judgment on the ground 

that the FDCA preempts the plaintiffs' state law claims because 

its products' labels comply with § 343(r)(6). The plaintiffs

responded that the labels' statements about glutamine are claims

about supplemental glutamine -- not naturally occurring glutamine

(glutamine that the body produces) -- and so to comply with 

§ 343(r)(6), Vitamin Shoppe needed to substantiate those claims

3 There is some sparring in the briefing about whether two 

additional claims on this product -- "[c]reatine helps to improve 

strength and performance during high intensity exercise and 

training" and "[b]eta-alanine helps support muscle strength, 

endurance and overall athletic performance" -- are at issue. 

Vitamin Shoppe contends that this appeal is limited to claims about 

glutamine. The plaintiffs insist that they have "always 

challenged" these two additional claims. But in their complaint, 

the plaintiffs bolded only the product's statement about 

glutamine, and their opposition to Vitamin Shoppe's motion for 

summary judgment did not contest the other claims. Thus, any 

appellate argument based on those claims is waived. See Davis v. 

Lucent Techs., Inc., 251 F.3d 227, 232 (1st Cir. 2001) ("[W]here 

a plaintiff fails to present arguments to the district court in 

opposition to a defendant's motion for summary judgment, we have 

refused to consider those arguments for the first time on 

appeal."). 
- 7 -

with evidence about supplemental glutamine. Because Vitamin 

Shoppe, they asserted, substantiated its claims about supplemental 

glutamine with evidence about naturally occurring glutamine, the

claims are not substantiated within the meaning of § 343(r)(6) and 

thus the FDCA does not preempt their state law claims. 

The district court granted summary judgment to Vitamin 

Shoppe, ruling that the FDCA preempts the plaintiffs' state law 

claims. In doing so, it held that the contested statements about 

glutamine are structure/function claims, that there is no 

"meaningful distinction" in the record between supplemental 

glutamine and naturally occurring glutamine, and that the parties' 

experts largely agreed that glutamine does what Vitamin Shoppe's 

labels claim. This appeal followed. 

II.

We review de novo the district court's order granting 

summary judgment. Perham, 57 F.4th at 335. Through that lens, 

we view the facts in the record in the light most favorable to the

plaintiffs, as the nonmovants, and draw all reasonable inferences 

in their favor.4 Id. The district court's preemption ruling is 

4 The parties disagree about whether we should defer to the 

district court's resolution of factual disputes subsumed within 

the preemption question: Vitamin Shoppe argues that we should 

review the court's findings for clear error, whereas the plaintiffs 

imply that we should disregard its findings and view the record in 

the light most favorable to them as the nonmovants. Because we 

would affirm the district court under either standard, we view the 

facts in the more appellant-friendly way -- in the light most 
- 8 -

reviewed de novo, too, because it "presents a pure question of 

law." Medicaid & Medicare Advantage Prods. Ass'n of P.R., Inc.

v. Hernández, 58 F.4th 5, 11 (1st Cir. 2023). 

III.

The plaintiffs argue that the district court erred by

holding that the FDCA preempts their state law claims because the 

statements about glutamine on Vitamin Shoppe's labels are not 

structure/function claims and, even if they were, Vitamin Shoppe

lacks substantiation that the statements are truthful and not 

misleading.5 We take each argument in turn. 

A.

We begin with whether the statements about glutamine on 

Vitamin Shoppe's labels are structure/function claims. Recall 

that a structure/function claim describes a nutrient's effect on 

the human body's structure or function or explains how the nutrient 

maintains that structure or function. § 343(r)(6)(A). Vitamin 

Shoppe's statements about glutamine fit the bill. 

First, the statement "[i]ntense exercise can deplete 

glutamine stores, however, supplemental glutamine is thought to 

replenish these stores allowing for enhanced recovery"6 explains 

favorable to the plaintiffs. 

5 The plaintiffs do not challenge the district court's 

conclusion that Vitamin Shoppe satisfied § 343(r)(6)'s other 

requirements. So we need not dwell on them. 

6 The plaintiffs concede that the other claim on the Glutamine 
- 9 -

how supplemental glutamine helps maintain glutamine stores, which 

help our muscles recover after intense exercise. So it fits 

comfortably within the definition of a structure/function claim. 

Indeed, the FDA has approved of a substantially similar claim: 

"[The] FDA believes that a claim that a product is useful because 

it counterbalances the effects of a drug in depleting a nutrient

. . . would be acceptable as a structure/function [claim]." 65 

Fed. Reg. at 1029. The plaintiffs assert that this statement 

"go[es] too far" because by referring to a "specific situation and 

usage," Vitamin Shoppe is claiming that the product itself has 

this beneficial effect. But their reading finds no support in the 

text of the statement. The statement claims that supplemental 

glutamine is thought to replenish glutamine stores after intense 

exercise -- not that taking the product will replenish glutamine 

stores after intense exercise. Although this distinction may be 

lost on consumers, it is a "form of finesse" that § 343(r)(6)(A) 

allows. Cf. Kaufman, 836 F.3d at 96 (stating that drawing a 

"distinction between the ingredient's function" and its effect on 

health "likely tricks many consumers," but the FDCA allows this 

"form of finesse"). 

supplement, which says that glutamine "is involved in regulating 

protein synthesis and has been shown to possess [a]nti-[c]atabolic 

properties to help preserve muscle," is a structure/function 

claim. 
- 10 -

Next, the statements that glutamine "helps support 

muscle growth and recovery as well as immune health" and has "anticatabolic properties" are structure/function claims, too. For 

each describes how glutamine affects a structure or function in 

the human body. And these claims are substantially similar to 

others that the FDA has blessed, such as "supports the immune 

system" and "boosts stamina, helps increase muscle size, and helps 

enhance muscle tone." See 65 Fed. Reg. at 1028–30. 

The plaintiffs nonetheless contend that these statements 

are not structure/function claims because they refer to the 

products -- not just to the nutrient glutamine. For example, the 

Glutamine supplement talks about supplemental glutamine (i.e., the 

form of the nutrient in the product), one of the statements about 

glutamine is prefaced by the phrase "[a]lso added [to the 

product]," and one of the labels says that the product "combines" 

three nutrients before listing each with a description of the 

nutrient's physiological role. The plaintiffs' contention is 

rooted in some language from Greenberg v. Target Corp., 985 F.3d 

650 (9th Cir. 2021). Greenberg, in emphasizing the differences 

between structure/function claims and another type of claim called 

disease claims, said that a structure/function claim does not 

"refer to the product itself." Id. at 654. A disease claim, in

contrast, "refers to a statement that the product itself can cure 

or treat a disease." Id. But Greenberg did not say that merely 
- 11 -

noting that the nutrient is in the product negates an otherwise 

acceptable structure/function claim. See id. Nor do we see any 

reason why it would. After all, a structure/function claim is 

about a nutrient or dietary ingredient in the product. See

§ 343(r)(6) (listing claims that can be made "for a dietary 

supplement"); 65 Fed. Reg. at 1002 (stating that the FDA's "final 

rule establishes criteria for determining whether a statement made 

about a dietary supplement is acceptable as a structure/function 

claim under section 403(r)(6)"). 

The plaintiffs' last line of attack is that a reasonable 

jury could construe the contested statements about glutamine as

claims about the products' benefits instead of claims about 

glutamine's effect on the human body. Assuming that the jury has 

a role to play in deciding whether a statement is a 

structure/function claim, no reasonable jury would construe the 

contested language as discussing the products' benefits instead of

glutamine's physiological role. The statements plainly make

claims about what glutamine does -- not about what the products 

do. That a consumer might hope or infer that the product will do 

what the nutrient does is a far cry from a reasonable jury finding 

that the words "nutrient X does Y" is best construed as meaning 

"product Z does Y because it contains nutrient X."7 

7 In the end, the plaintiffs all but abandon their argument 

that the contested statements are not structure/function claims. 
- 12 -

In sum, because the contested statements about glutamine 

on Vitamin Shoppe's labels describe glutamine's effect on the human 

body's structure or function or explain how glutamine maintains 

that structure or function, they are structure/function claims 

under § 343(r)(6)(A). 

B.

The plaintiffs argue next that the FDCA does not preempt 

their state law claims because Vitamin Shoppe failed to

substantiate its products' statements about glutamine. They 

assert that the evidence substantiating each structure/function 

claim must be about the supplemental form of the nutrient. Because 

the district court, they say, looked at evidence about naturally 

occurring glutamine rather than supplemental glutamine, it did not

realize that Vitamin Shoppe's statements about glutamine are 

bereft of evidentiary support. 

To make a structure/function claim, the manufacturer 

must "ha[ve] substantiation that [the claim] is truthful and not 

misleading." § 343(r)(6)(B). The term "substantiation" is not 

defined. Kaufman, 836 F.3d at 93. But the FDA's guidance defines 

it as "competent and reliable scientific evidence." Id. (quoting 

They say in their reply brief that "the best and most consistent 

position may be . . . that the claims here are proper-in-form 

structure/function claims." And at oral argument, they conceded 

that the statements are structure/function claims at "some level."
- 13 -

Food & Drug Admin., Guidance for Industry: Substantiation for 

Dietary Supplement Claims Made Under Section 403(r)(6) of the 

Federal Food, Drug, and Cosmetic Act Part I.B. (Dec. 2008), 

http://www.fda.gov/food/guidanceregulation/guidancedocumentsregu

latoryinformation/dietarysupplements/ucm073200.htm [hereinafter 

Guidance for Industry]). Because we have used that definition 

before, see id., and both parties use it, we will also do so here. 

Thus, to comply with § 343(r)(6)(B), Vitamin Shoppe must have 

competent and reliable scientific evidence that its 

structure/function claims about glutamine are truthful and not 

misleading. Before we decide whether it has that evidence, we 

resolve first a dispute about which form of glutamine the evidence 

must be about.

The plaintiffs argue that the evidence substantiating 

Vitamin Shoppe's structure/function claims about glutamine must be 

about the supplemental form, not the naturally occurring form. 

They are right for the simple reason that Vitamin Shoppe's claims 

are about supplemental glutamine and so its substantiation must 

be, too. One of the labels openly talks about what "supplemental 

glutamine" does. On another label, the statement about glutamine 

is prefaced by the phrase "[a]lso added," which means that the 

claim is about supplemental glutamine -- the glutamine added to 

the product -- not naturally occurring glutamine. The statement 

about glutamine on the third label appears in a list of three 
- 14 -

nutrients "combine[d]" in the product. So this statement also 

refers to the form of glutamine in the product. Because the 

structure/function claims here are about supplemental glutamine,

"substantiation that [the claims are] truthful and not misleading" 

must be about supplemental glutamine, too.8 See § 343(r)(6)(B).

But in the end, the distinction between naturally 

occurring glutamine and supplemental glutamine is, as the district 

court said, meaningless. At oral argument, we asked the 

plaintiffs if supplemental glutamine and naturally occurring 

glutamine play the same role in the human body. The plaintiffs 

conceded that, on this record, they do. Our review of the record 

reveals only one difference between them: The parties' experts 

agreed that our bodies may struggle absorbing supplemental 

glutamine and that therefore much of it may be lost during 

digestion. But some of it survives. Indeed, the plaintiffs' 

8 The plaintiffs' "first reason" why evidence about 

supplemental glutamine is required (i.e., that the claims are about 

supplemental glutamine) suffices here. They nonetheless ask us 

to go further: They ask us to hold that every structure/function 

claim must be substantiated by evidence about the supplemental 

form of the nutrient. We see no reason to set down a hardline

rule in a case that does not call for one, especially given the 

wide array of substances in dietary supplements and the wide array 

of forms they take. See 21 U.S.C. § 321(ff) (defining "dietary 

supplement" as a product that, among other things, contains "a 

vitamin," "a mineral," "an herb or other botanical," "an amino 

acid," "a dietary substance for use by man to supplement the diet 

by increasing the total dietary intake," or "a concentrate, 

metabolite, constituent, extract, or combination of any ingredient 

described").
- 15 -

expert acknowledged that some people -- such as those who exercise 

intensely or have suffered physical trauma, severe illness, 

surgery, or burns -– benefit from taking supplemental glutamine. 

So where does that leave the disagreement between the parties? 

The plaintiffs contended at oral argument that Vitamin Shoppe loses 

on substantiation "if you take a pill and it does not actually 

affect the body's structure or function as the label claims." 

Section 343(r)(6)(B), they said, requires "efficacy that the 

product supports the body's structure or function as claimed." 

Vitamin Shoppe argues that the plaintiffs are seeking to impose a 

substantiation requirement above and beyond what the plain text of 

§ 343(r)(6)(B) requires. 

With the facts and arguments ironed out, this case now 

looks a lot like Greenberg. The issue there was whether Target 

had substantiation that its claim that biotin "helps support 

healthy hair and skin" was truthful and not misleading when the 

evidence showed that most people get the biotin they need through 

their diet and thus taking biotin is useless for all but a select 

few who have a biotin deficiency. Greenberg, 985 F.3d at 652–53. 

The appellant argued that Target's "structure/function claim must 

be true not only as to the nutrient itself but [also as to] the 

product as a whole." Id. at 655. Greenberg rejected that 

argument based on the plain text of the FDCA. A structure/function 

claim, it said, "addresses only the general role of an 
- 16 -

ingredient/nutrient on the human body," not "the product's health 

impact on the general population." Id. at 655–56. Thus, the 

manufacturer need only have substantiation that its claim about 

"the ingredient's function on the human body" is truthful and not 

misleading. Id. at 656. 

We agree with Greenberg that the plain text of 

§ 343(r)(6)(B) requires a manufacturer to have substantiation that 

a nutrient's claimed effect on the human body's structure or 

function is truthful and not misleading, not that the product has

the claimed effect. Section 343(r)(6)(B) requires "the 

manufacturer of the dietary supplement [to] ha[ve] substantiation 

that such statement" -- i.e., the statement that describes the 

nutrient's effect on the human body's structure or function -- "is 

truthful and not misleading." Nowhere in the text of 

§ 343(r)(6)(B) is the manufacturer required to show that taking

the dietary supplement affects the structure or function as 

claimed. See United States ex rel. Heineman-Guta v. Guidant 

Corp., 718 F.3d 28, 35 (1st Cir. 2013) ("We will not ordinarily 

read requirements into a statute that 'do not appear on its face.'"

(quoting Dean v. United States, 556 U.S. 568, 572 (2009))). 

Had Congress wanted to add an efficacy requirement to 

§ 343(r)(6)(B), it could have. Products that are regulated as 

drugs have an efficacy requirement. The FDA will deny an 

application to sell a new drug if, among other things, "there is 
- 17 -

a lack of substantial evidence that the drug will have the effect 

it purports or is represented to have under the conditions of use 

prescribed, recommended, or suggested." 21 U.S.C. § 355(d); see 

also Mut. Pharm. Co. v. Bartlett, 570 U.S. 472, 476 (2013) 

(describing the new-drug application and approval process). And 

there is a reason why structure/function claims may not purport to 

treat disease and why a product bearing such claims must expressly 

repudiate any intention of treating disease: A dietary supplement 

that makes a disease claim is regulated as a drug and must meet 

the efficacy requirement discussed above. See 21 C.F.R. 

§ 101.93(f); § 355(d). So Congress knows how to add an efficacy 

requirement when it wants to and intentionally excluded one from 

structure/function claims. See Guidant Corp., 718 F.3d at 35

("[W]hen Congress includes language in one section of a statute 

but omits it in another, 'it is generally presumed that Congress 

acts intentionally and purposely in the disparate inclusion or 

exclusion.'" (quoting Keene Corp. v. United States, 508 U.S. 200, 

208 (1993))). 

There is more. Congress found in the DSHEA that "safety 

problems with [dietary] supplements are relatively rare" and that 

"legislative action that protects the right of access of consumers 

to safe dietary supplements is necessary in order to promote 

wellness." § 2(14), (15)(A), 108 Stat. at 4326. It enacted the 

DSHEA to "ensur[e] that the Federal Government erects no barriers 
- 18 -

that impede the ability of consumers to improve their nutrition 

through the free choice of safe dietary supplements" and "to 

clarify that dietary supplements are not drugs . . . [and] should 

not be regulated as drugs." S. Rep. No. 103-410 (1994), 1994 WL 

562259, at *2. Needless to say, Congress intended dietary 

supplements to escape the regulatory gauntlet that drugs must go 

through.9 

The plaintiffs have a back-up argument. Putting aside 

§ 343(r)(6)(B)'s text, they contend that we must defer to the FDA's 

guidance about substantiation, which, they say, "requires 

substantiation of actual efficacy of the supplement." It is true 

that the FDA's guidance opines that manufacturers should have 

evidence that their dietary supplements affect the human body's 

structure or function as claimed and under the conditions of use 

recommended on the products' labels. Guidance for Industry, 

supra, Part II.B–D. But the guidance calls itself a nonbinding 

9 Our conclusion is bolstered by several law review articles 

that the district court cited. See Ferrari v. Vitamin Shoppe, 

Inc., No. 17-10475-GAO, 2022 WL 974048, at *3 (D. Mass. Mar. 31, 

2022). The DSHEA appears to be the result of intense lobbying by 

dietary supplement manufacturers and consumers in response to 

proposals to heavily regulate dietary supplements. See Lars Noah 

& Barbara A. Noah, A Drug by Any Other Name . . . ?: Paradoxes in 

Dietary Supplement Risk Regulation, 17 Stan. L. & Pol'y Rev. 165, 

166 (2006); Peter J. Cohen, Science, Politics, and the Regulation 

of Dietary Supplements: It's Time to Repeal DSHEA, 31 Am. J.L. & 

Med. 175, 179–180 (2005); Stephen H. McNamara, Dietary Supplements 

of Botanicals and Other Substances: A New Era of Regulation, 50 

Food & Drug L.J. 341, 341 (1995). 
- 19 -

recommendation "unless specific regulatory or statutory 

requirements are cited." Id. Part I.A.; see also Greenberg, 985 

F.3d at 656 n.3 (stating that this guidance is "not on-point and 

in any event [is] not binding"). And we see no statutory or 

regulatory authority backing its opinion that, for a 

structure/function claim to be substantiated within the meaning of 

§ 343(r)(6)(B), the manufacturer must have evidence that the 

nutrient plays the physiological role claimed under the conditions 

of use recommended on the label. Assuming (without deciding) that 

the guidance is the type of agency interpretation warranting

Chevron deference, see Doe v. Leavitt, 552 F.3d 75, 79–80 (1st 

Cir. 2009), our analysis above about why the plain text of 

§ 343(r)(6)(B) only requires substantiation that the 

structure/function claim is truthful and not misleading dooms the 

plaintiffs' Chevron argument. See Saysana v. Gillen, 590 F.3d 7, 

16 (1st Cir. 2009) ("We have concluded that the text of the statute 

is clear. Consequently, . . . there is nothing for the agency to 

interpret -- no gap for it to fill -- and there is no justification 

for resorting to agency interpretation to address an ambiguity.").

We turn now to whether Vitamin Shoppe has substantiation 

that its structure/function claims are truthful and not 

misleading. Recall that substantiation requires competent and 

reliable scientific evidence. The plaintiffs claim that Vitamin 

Shoppe put forward evidence only about how naturally occurring 
- 20 -

glutamine –- not supplemental glutamine -- affects the human body's 

structure or function. But the record tells a different story. 

Vitamin Shoppe's expert, Dr. Hoffman, presented a myriad of studies 

showing that glutamine supplementation supports immune health and

muscle growth and recovery; is involved in regulating protein 

synthesis; has anti-catabolic effects, which help preserve muscle;

and may help replenish glutamine stores after intense exercise. 

The plaintiffs' expert, Dr. Candow, attacked these studies on 

several grounds, including that they used higher doses of glutamine 

than Vitamin Shoppe's labels recommend, involved different forms 

of administration (e.g., intravenous), incorporated other 

additives, used animal subjects, and used disease-state human 

subjects. In crafting his report, Dr. Candow evaluated Vitamin 

Shoppe's structure/function claims with respect to healthy humans 

at the doses recommended on the labels. And after evaluating each 

claim through this lens, he concluded that glutamine 

supplementation at the doses recommended is useless. He did, 

however, agree that glutamine supplementation at some dose and for 

some people affects the human body's structure or function as 

Vitamin Shoppe's labels claim. Because the plaintiffs assert that 

he was talking about naturally occurring glutamine when he said 

that, we will address each claim to show that there is no genuine 

dispute between the experts that supplemental glutamine plays the 

physiological role that Vitamin Shoppe's labels claim. 
- 21 -

We start with the claim that glutamine supplementation 

supports muscle growth and recovery and immune health. The 

following exchanges took place at Dr. Candow's deposition: 

Q. Now, going to the glutamine statement which 

says, "Glutamine helps support muscle growth 

and recovery as well as immune health." 

A. Okay. 

Q. Is it your opinion that this statement is 

false? 

A. Yes. Specifically to the dose that is 

recommended. 

. . . . 

[Q.] At what dosage does glutamine help 

support immune health? 

A. I believe in all the articles the minimum 

dose was 10 grams a day. 

. . . . 

Q. Has glutamine supplementation been shown to 

decrease the incidence of infections? 

A. I believe so. I believe so, yes. 

Q. Has glutamine been shown to improve the 

response of cells in the immune system? 

A. Yes. 

. . . .

Q. And do you disagree that glutamine 

supplementation can cause an increase in 

recovery? 

A. It can only at a specific dosage. 

Q. But in general, glutamine supplementation 

can increase recovery in the body? 

A. Again, at a specific dosage. So 1 gram, 

no. 2 grams or the dosage here is a specific 

dosage. 

Q. What is the dosage at which

glutamine . . . supports recovery?

A. I believe the minimal amount was 6 grams.

. . . . 

Q. Glutamine supplementation can increase 

muscle protein synthesis 10 and prevent

10 Dr. Candow states in his report, "Muscle growth reflects 

the net balance between muscle protein synthesis and protein 

breakdown . . . . Muscle growth may be the result of a decrease 

in protein breakdown, an increase in protein synthesis, or both." 
- 22 -

metabolism in certain situations. Correct? 

A. That's correct. 

Thus, Dr. Candow's dispute with this structure/function claim 

comes down to the dose recommended on the product. The same is 

true for the other claims. As for the claim that taking 

supplemental glutamine after intense exercise is thought to 

replenish depleted glutamine stores, leading to enhanced recovery, 

Dr. Candow agreed that, as a general matter, intense exercise can 

deplete glutamine stores and that glutamine supplementation can 

help maintain these stores and enhance recovery. He also agreed 

that supplemental glutamine is involved in regulating protein 

synthesis. And he agreed that supplemental glutamine, in some 

circumstances such as in disease-state humans,11 has anti-catabolic 

properties, which help preserve muscle tissue by preventing 

protein breakdown. Thus, there is no genuine dispute that Vitamin 

Shoppe has substantiation that its claims about supplemental 

glutamine's physiological role are truthful. 

The plaintiffs have one more arrow in their quiver. 

They argue that Vitamin Shoppe's labels are nonetheless misleading 

By agreeing that glutamine supplementation increases muscle 

protein synthesis, he agreed that glutamine supplementation 

supports muscle growth. 

11 Dr. Candow explained that humans might need more glutamine 

than we naturally produce during times of extreme physical stress, 

such as trauma, cancer, HIV/AIDS, surgery, burns, sepsis, 

radiation, chemotherapy, and intense exercise. 
- 23 -

because they fail to reveal material facts about taking the 

supplements as recommended (i.e., that taking the supplements as 

recommended does nothing). Section 343 governs when food 

products, including dietary supplements, are misbranded. 21 

U.S.C. § 343. Section 321(n) provides that when evaluating 

whether a product is misbranded because the labeling is misleading, 

we must consider, among other things:

[T]he extent to which the labeling . . . fails 

to reveal facts material in . . . light of 

[the] representations [on the label] or 

material with respect to consequences which 

may result from the use of the [product] to 

which the labeling . . . relates under the 

conditions of use prescribed in the labeling

. . . thereof or under such conditions of use 

as are customary or usual.

Id. § 321(n); see also Kaufman, 836 F.3d at 95 ("This statutory 

command that we consider the omission of material facts fits handin-glove with the mandate of section 343(r)(6)(B) that the seller's 

substantiation show that a [claim] is both 'truthful and not 

misleading.'" (quoting § 343(r)(6)(B))). The question here is 

whether omitting the fact that glutamine supplementation is 

useless at the doses prescribed on the labels renders Vitamin 

Shoppe's claims about glutamine's physiological role misleading. 

In Greenberg, the Ninth Circuit answered no. It reasoned that if

a true claim such as "vitamin C boosts immunity" is misleading 

because most people do not need nor benefit from taking vitamin C, 

then "virtually any structure/function claim for dietary 
- 24 -

supplements would potentially be misleading to the great majority 

of people" because most people are not walking around with vitamin 

deficiencies. Greenberg, 985 F.3d at 656. Such an outcome, it 

said, would conflict with the FDCA's text and Congress's purpose 

in enacting a regulatory carve-out for structure/function claims. 

Id. We agree. Section 343(r)(6)(B) requires the manufacturer to 

have substantiation that its claim about a nutrient's 

physiological role is not misleading. That taking the product as 

directed does not reap the benefits the label attributes to the 

nutrient has nothing to do with whether the nutrient's claimed 

physiological role is misleading. See id. ("[M]anufacturers may 

make structure/function claims about a nutrient's general role on 

the human body without disclosing whether the product will provide 

a health benefit to each consumer.").

To be sure, a structure/function claim is misleading if 

it omits a nutrient's conflicting or harmful role in affecting the 

human body's structure or function. See Kaufman, 836 F.3d at 95–

96 (failing to disclose the nutrient's harmful effect on the human 

body's structure or function plausibly renders a 

structure/function claim misleadingly incomplete). And a 

structure/function claim is untruthful if the nutrient does not 

have the claimed effect. See Kroessler v. CVS Health Corp., 977 

F.3d 803, 812 (9th Cir. 2020) (reversing dismissal of the 

plaintiff's complaint on preemption grounds where the plaintiff
- 25 -

alleged that glucosamine does not have the claimed effect on the 

human body's structure or function). But this is not such a case. 

Because the experts here agree that Vitamin Shoppe's claims about 

glutamine's physiological role are truthful and there is no 

contention that these claims are misleading as to that role, 

Vitamin Shoppe has complied with § 343(r)(6)(B). 

IV.

The statements about glutamine on Vitamin Shoppe's 

labels are structure/function claims under § 343(r)(6). And 

Vitamin Shoppe has complied with the FDCA's requirements to make

such claims. The plaintiffs' state law claims attacking those 

statements are therefore expressly preempted by the FDCA. The

district court's judgment is affirmed.