Most whole-food protein sources are naturally gluten-free — the real risk for anyone managing celiac disease or gluten sensitivity is in processed protein products, where gluten shows up as a binder, filler, or cross-contamination risk more often than people expect.
Naturally gluten-free by default
All meat, poultry, fish, shellfish, eggs, dairy, legumes, and most nuts and seeds on this site are naturally gluten-free in their unprocessed form. Among plant proteins specifically, tofu, tempeh (verify the specific brand — some blend in grains), and quinoa are naturally gluten-free complete or near-complete proteins.
The obvious gluten sources
Seitan is pure wheat gluten by definition — the name literally describes the ingredient — and is one of the very few whole "foods" that's entirely off-limits. Ezekiel bread contains wheat and barley as core ingredients despite its health-food branding.
Where gluten hides less obviously
Standard soy sauce (used in some tempeh, marinades, and flavored tofu) usually contains wheat unless labeled tamari or specifically gluten-free. Some flavored jerky and protein bars use barley malt or wheat-derived ingredients as flavoring or binders. Oats are naturally gluten-free as a grain, but are extremely commonly cross-contaminated during processing unless specifically labeled "certified gluten-free oats" — a detail worth checking every time for anyone with celiac disease rather than gluten sensitivity, given how much lower the safe threshold is for celiac specifically.
Protein powder and gluten
Whey, casein, pea, and most single-ingredient plant protein powders are naturally gluten-free — the risk shows up more in flavored, blended products with added thickeners or flavor systems that can include gluten-derived ingredients. Checking for a certified gluten-free label matters more for celiac disease specifically than for general gluten sensitivity, given the much lower safe threshold involved.