This code system http://terminology.hl7.org/CodeSystem/diet defines the following codes:

CodeDisplayDefinition
vegetarian VegetarianFood without meat, poultry or seafood.
dairy-free Dairy FreeExcludes dairy products.
nut-free Nut FreeExcludes ingredients containing nuts.
gluten-free Gluten FreeExcludes ingredients containing gluten.
vegan VeganFood without meat, poultry, seafood, eggs, dairy products and other animal-derived substances.
halal HalalFoods that conform to Islamic law.
kosher KosherFoods that conform to Jewish dietary law.
 <status value="draft"/> <experimental value="false"/> <date value="2023-02-25T11:07:30-07:00"/> <publisher value="FHIR Project team"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> </contact> <description value="This value set defines a set of codes that can be used to indicate dietary preferences or restrictions a patient may have."/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/encounter-diet"/> <content value="complete"/> <concept> <code value="vegetarian"/> <display value="Vegetarian"/> <definition value="Food without meat, poultry or seafood."/> </concept> <concept> <code value="dairy-free"/> <display value="Dairy Free"/> <definition value="Excludes dairy products."/> </concept> <concept> <code value="nut-free"/> <display value="Nut Free"/> <definition value="Excludes ingredients containing nuts."/> </concept> <concept> <code value="gluten-free"/> <display value="Gluten Free"/> <definition value="Excludes ingredients containing gluten."/> </concept> <concept> <code value="vegan"/> <display value="Vegan"/> <definition value="Food without meat, poultry, seafood, eggs, dairy products and other animal-derived substances."/> </concept> <concept> <code value="halal"/> <display value="Halal"/> <definition value="Foods that conform to Islamic law."/> </concept> <concept> <code value="kosher"/> <display value="Kosher"/> <definition value="Foods that conform to Jewish dietary law."/> </concept> </CodeSystem>