By SmashMeals Editorial · Published · Updated
If you have celiac disease, you have probably been told two things that seem to conflict. First, a food labeled gluten-free can legally contain a tiny amount of gluten. Second, even a crumb matters. Both are true, and a 2026 study in Gastroenterology helps explain why.
What "gluten-free" means on a U.S. label
The FDA's gluten-free labeling rule, issued in 2013, lets a packaged food carry a gluten-free claim if it meets a defined standard: less than 20 parts per million (ppm) of gluten, among other requirements. The claim is voluntary. A 2020 rule added compliance requirements for fermented and hydrolyzed foods such as yogurt, sauerkraut and hydrolyzed plant proteins.
Parts per million describes concentration, not amount. The gluten you actually eat depends on how much of the food you eat. That is the part most people never get told.
| Food at 20 ppm gluten | Serving | Gluten in that serving |
|---|---|---|
| Snack or cracker | 1 oz (28 g) | About 0.56 mg |
| Bowl of cereal | 2 oz (57 g) | About 1.1 mg |
| Plate of pasta | 4 oz dry (113 g) | About 2.3 mg |
| Several items across a day | 8 oz total (227 g) | About 4.5 mg |
These are worst-case numbers for foods at the legal limit. Independent testing by Gluten Free Watchdog has found most labeled gluten-free foods test far lower: 92% of the products it tested in 2025 were below 5 ppm, the lowest level its standard test can measure.
What the 2026 threshold study found
Researchers in Australia ran a randomized, double-blind, placebo-controlled study, published in Gastroenterology (Daveson and colleagues, 2026). They enrolled 51 adults with biopsy-confirmed celiac disease who had been gluten-free for more than two years. Each person received three single gluten "challenges" four weeks apart, at doses from 1 mg to 1,000 mg, or a placebo.
The researchers measured interleukin-2 (IL-2), an immune signal that rises within hours when gluten-reactive immune cells switch on. According to a summary in HMP Global's gastroenterology news:
- At 1,000 mg and 610 mg, 83% of challenges triggered an IL-2 rise.
- At 90 mg, 36% did. At 3 mg to 13 mg, 17% to 27% did.
- At 2 mg, 1 mg and placebo, none did.
- The modeled dose that would trigger a response in 10% of people was about 2.4 mg.
Just as important: symptoms were not a reliable guide. Symptom scores at doses under 1,000 mg did not rise above placebo, even when the immune system was reacting. The authors concluded that IL-2 release happens at gluten doses below current labeling thresholds.
What the study does not prove
The study measured a short-term immune signal after one dose. It did not show intestinal damage from these small amounts, and the authors note the long-term consequences of brief low-dose immune activation are unknown. Fifty-one people is a small group, and the estimates have wide margins. It does not mean the 20 ppm rule is wrong for everyone, and it does not tell any one person their personal threshold.
What it does show is that "I felt fine" is not proof that gluten did nothing. That is a strong reason to reduce small, repeated exposures where you can.
Where small exposures really come from
For most people with celiac disease, the biggest risks are not a certified gluten-free product at 19 ppm. They are everyday cross-contact:
- Shared toasters, fryers, colanders and cutting boards.
- Flour in the air or on surfaces in a kitchen that also bakes with wheat.
- Serving spoons that move between dishes at a buffet or potluck.
- Restaurant and catering kitchens where a gluten-free item is made on the same line as regular food.
- Oats that are not specifically labeled gluten-free.
How to lower your exposure day to day
| Situation | Lower-risk habit |
|---|---|
| Packaged food | Choose products labeled gluten-free; consider third-party certified products for staples you eat often. |
| Home kitchen | Keep a separate toaster, colander and cutting board, or make the kitchen fully gluten-free. |
| Eating out | Ask whether gluten-free items share fryers, grills, prep space or utensils with regular food. |
| Prepared meals | Ask whether the kitchen also produces wheat-based food, and how it prevents cross-contact. |
| Follow-up care | Ask your gastroenterologist about follow-up testing and a dietitian referral. |
Why we built a dedicated kitchen
SmashMeals operates a dedicated gluten-free kitchen. A dedicated gluten-free kitchen means SmashMeals does not run a regular wheat-based production line beside a gluten-free line. The purpose of that model is to reduce the in-kitchen shared-production pathways customers otherwise have to investigate.
Cross-contact can still occur at many points in the food system, including before ingredients arrive at a kitchen, and gluten is not the only allergen. Review the ingredients and allergen information for each meal and contact us with questions before ordering. Read our gluten-free standards, see inside our kitchen, and check this week's menu.
If you were diagnosed recently, our newly diagnosed celiac meal guide covers the first weeks. For news on medicines in development, see our 2026 celiac treatment pipeline guide.
Sources
Frequently asked questions
- What does 20 ppm gluten mean?
- Twenty parts per million means 20 milligrams of gluten per kilogram of food. A 1-ounce serving of a food at exactly 20 ppm contains about 0.56 mg of gluten.
- What did the 2026 gluten threshold study find?
- In 51 adults with celiac disease, single doses of 3 mg to 13 mg triggered an immune signal in 17% to 27% of challenges, while 2 mg and below triggered none. Symptoms were unreliable at doses under 1,000 mg.
- Is the FDA's 20 ppm limit unsafe?
- The study does not prove that. It measured a short-term immune signal, not intestinal damage. Most labeled gluten-free foods test well below 20 ppm. The bigger everyday risk is usually cross-contact from shared kitchens and utensils.