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Issue #56 (June 2019)

From the Editor

Volume 1

In this volume of the NERD, we cover an interesting and important article examining gluten contamination of foods labelled as gluten-free in restaurants across the United States. The study took a look at data shared by the owners of a portable device that can detect gluten in foods.

In the United States, the Food and Drug Administration has a rule in place since 2013 that packaged foods having a gluten-free label must contain under gluten at levels under 20 parts per million. The rationale for choosing this number is that it’s on the edge of the range which gluten can be detected reliably using common analytical techniques. The thing is that this rule doesn’t apply to foods served in restaurants, which raises the possibility that eating out can potentially expose diners to gluten. This makes the portable device used in the article we cover in this volume a potentially useful tool for people who have celiac disease or non-celiac gluten sensitivity.

The device can be linked to an app where users can opt to share their data both with the manufacturer and other users. Sharing which restaurants in an area have minimal gluten contamination can be very useful when trying to find celiac-friendly restaurants. The data shared with the manufacturer was what went into the analysis we cover in this volume. The study found that 32% of restaurant foods labelled as gluten free were contaminated with gluten. While this result is an interesting starting point and clearly shows that there are indeed plenty of “gluten-free” restaurant foods that don’t live up to the label, the specific numbers they found shouldn't be taken too seriously, since the sample they used wasn’t random.

The concept of sampling is extremely important in making sure that you can use numbers like this. Ideally, we’d like to say that since this study found that 32% of the supposedly gluten-free foods sampled contained gluten, this is evidence that around 32% (plus or minus a margin of error) of all restaurant foods labelled gluten free may also contain gluten. In doing this, we’re making an inference about the sample’s properties to the population of all restaurant foods in the U.S. Unfortunately, we can’t make this inference from these data, since they were obtained through owners of this specific device volunteering to share their data. This kind of voluntary sampling can easily introduce bias. Maybe people who live in areas where they’ve been exposed to gluten are more likely to own the device and be more willing to share the data. That would make the actual rate of gluten contamination higher than what was found here. Or, perhaps device owners tend to be more savvy in their restaurant choices than non-owners, which would make the estimate lower than the rate across all U.S. restaurants. Random sampling, where all foods have an equal chance of being tested, would eliminate these biases, but is often hard to do well. There are other kinds of techniques that could have raised the chances of reducing biases by getting a more representative sample from the population, but unfortunately they weren't used in the study, either.

So, while we can say that around 32% of this sample’s gluten-free labelled foods contain gluten, we can’t quite tell how much of a problem gluten contamination is nationwide based on this paper alone. The details really do matter when interpreting studies.

Gregory Lopez, MA, PharmD
Editor-in-chief, Nutrition Examination Research Digest


Volume 2

Back in February of 2019, the United States Food and Drug Administration (FDA) announced a series of efforts whose goal was to modernize how the agency oversees dietary supplements. The initiatives they announced included creating a public-private partnership group to explore ways to test the safety and efficacy of botanical supplements, modernizing the process for submitting new dietary ingredient notifications, and developing the Dietary Supplement Ingredient Advisory List. The list’s purpose is to rapidly alert the public to ingredients that the FDA has discovered may be unlawfully included in supplements or unlawfully marketed in the United States. The advisory list was released in April. The list is meant to be continuously updated in order to alert the public to new ingredients, and to remove previously listed ingredients which have met the FDA’s standards. Since its release, it’s been updated a few times. You can find the latest version here.

This list can be useful, but needs to also be interpreted properly. The list’s sole goal is to alert people to ingredients that are unlawful to include in dietary supplements. This list makes it clear to manufacturers which ingredients are off limits to include in their products for now, and also allows the public to avoid supplements containing these unlawful ingredients if they wish. The question is: is it a good idea to avoid supplements containing these ingredients? My answer is “yes!” To understand why, let’s take a too-quick tour how dietary supplements are regulated.

In the United States, dietary supplements are regulated under the Dietary Supplement Health and Education Act (DSHEA), which was passed in 1994. This act spells out what kinds of ingredients are okay to include in dietary supplements. In short, either dietary ingredients that were marketed in the U.S. prior to the passage of the DSHEA, or dietary ingredients which manufacturers told the FDA about through a new dietary ingredient notification can be lawfully included in dietary supplements.

This matters for safety. New dietary ingredient notifications that are sent to the FDA require some justification for thinking that the ingredient is safe. This is done through a comprehensive safety profile, where the manufacturer lays out all the available safety evidence, both published and unpublished from both humans and animals. Grandfathered ingredients that were marketed in the U.S. prior to the passage of the DSHEA don’t need this kind of justification. However, the fact that they’ve been on the market for a while and haven’t been pulled provides some imperfect evidence to think that they’re somewhat safe.

This means that dietary ingredients appearing on the Dietary Supplement Ingredient Advisory List may not have the basic evidence for safety that the FDA requires. This doesn’t imply that there’s evidence these ingredients are unsafe; but I’d much rather have some assurance of safety, however limited that assurance may be. That’s why I’d recommend avoiding supplements containing ingredients on the latest version of the Advisory List. When it comes to taking supplements, better safe than sorry.

Gregory Lopez, MA, PharmD
Editor-in-chief, Nutrition Examination Research Digest

See other articles in Issue #56 (June 2019) of Study Deep Dives.