On Gluten and Celiac

Oct 20, 2025

Comment Print
Share on:

Introduction

What Foods Contain Gluten?

Celiac Disease

Gluten Challenge
If you're going to be tested for Celiac disease, whether it's a blood test or an endoscopy, it's typically recommended you undergo what's known as a "gluten challenge". This involves eating a large amount of gluten for a period of time. Otherwise, you may end up with a false negative, and little to no consumption of gluten causes the small intestine to heal itself if you have Celiac. Sounds great right? Yes, but that leads to an inaccurate test for Celiac. Thus, a gluten challenge is initiated.

Typically, a gluten challenge involves eating the equivalent of 4-5 slices of bread worth of gluten for a period of 2-4 weeks before testing for Celiac disease. But what does this actually mean? How much gluten can you consume besides bread?

Let's assume a standard loaf of bread. Each slice weighs 29 g, and contains 3.1 g of protein. Since approximately 80% of protein in bread is made up of gluten, we can therefore conclude that 5 slices of bread contains approximately 12.4 g of gluten.

In the table below, I will break down the amount of gluten contained in certain foods; per serving size, per 100 g, and per 100 calories. Note that data for the amount of gluten in specific grains is not always present. Therefore, I will be assuming the following:

50% of the protein found in rye is made up of gluten
50% of the protein found in barley is made up of gluten
75% of the protein found in wheat-based products is made up of gluten (such as white flour, whole wheat flour, couscous, farro, and spelt)
100% of the protein in vital wheat gluten is made up of gluten

Foods High in Gluten

Grains (Raw)

Food	Serving Size	Gluten Per Serving	Gluten Per 100 g	Gluten Per 100 cal
Barley	1/4 cup (50 g)	2.5 g	5.0 g	1.4 g
Couscous	1/4 cup (56 g)	5.4 g	9.6 g	2.6 g
Farro	1/4 cup (45 g)	4.3 g	9.5 g	2.8 g
Rye	1/4 cup (42 g)	2.2 g	5.2 g	1.5 g
Spelt	1/4 cup (44 g)	4.8 g	11.0 g	3.3 g
Vital Wheat Gluten	1/4 cup (30 g)	22.6 g	75.2 g	20.3 g
White Wheat	1/4 cup (31 g)	2.4 g	7.7 g	2.1 g
Whole Wheat	1/4 cup (31 g)	3.1 g	9.9 g	2.9 g

Other

Food	Serving Size	Gluten Per Serving	Gluten Per 100 g	Gluten Per 100 cal
Beer	12 oz (360 g)	1.1 g	0.3 g	0.7 g
Marmite	1/2 tsp (4 g)	1.0 g	25.0 g	10.0 g
Soy Sauce (Shoyu)	1 tbsp (15 g)	0.9 g	6.1 g	11.5 g

Highest Sources of Gluten
Per serving: [TODO] - [TODO] mg ([TODO])
Per 100 g: [TODO] - [TODO] mg
Per 100 cal: [TODO] - [TODO] mg

Sources

This post may contain affiliate links