Can I Eat Mustard on a Low Iodine Diet? Your Complete Guide

December 11, 2025 •

4 min read

According to USDA data, a single teaspoon of plain yellow mustard contains a very small amount of iodine, making it generally acceptable for a low iodine diet. The main concern for those on this specific diet is not the mustard itself, but the type of salt and other additives used in its preparation. This guide will help you determine if you can eat mustard on a low iodine diet safely.

Quick Summary

Mustard is typically safe on a low-iodine diet, provided you check the ingredients carefully. Most homemade and commercial versions made with non-iodized salt are acceptable, while processed or unknown brands should be avoided to manage iodine intake.

Key Points

Check Labels: Always read the ingredient list to ensure mustard does not contain iodized salt, sea salt, or dairy products.
Prioritize Homemade: Making your own mustard from scratch is the safest way to ensure all ingredients are low-iodine.
Understand Goitrogens: The goitrogens in mustard seeds are not a significant concern for a short-term, low-iodine diet, especially since commercial mustard is processed.
Plain is Safest: Simple yellow or spicy brown mustards are more likely to be LID-compliant than honey mustard or other flavored varieties.
Consult a Professional: If you are ever unsure about a specific brand or ingredient, consult your doctor or a dietitian specializing in low-iodine diets.

Mustard on a Low Iodine Diet: A Closer Look

Many patients preparing for radioactive iodine (RAI) treatment are placed on a short-term, low-iodine diet (LID) to "starve" thyroid cells of iodine. This makes them more receptive to the radioactive iodine treatment. Naturally, questions arise about common condiments like mustard. The good news is that plain mustard is generally considered safe for the LID, but the specific ingredients and brand matter. The key is to avoid sources of high iodine, such as iodized salt, seaweed, and dairy. Since mustard is made from mustard seeds, vinegar, and spices, its core ingredients are low in iodine. The risk lies in added ingredients, particularly the salt.

The Salt Dilemma: Iodized vs. Non-Iodized

For the low-iodine diet, all forms of iodized salt and sea salt are off-limits due to their high iodine content. Most commercially prepared and processed foods, including many condiments, use iodized salt. This is why careful label-reading is essential. Non-iodized salt may be used instead.

What to look for on the label:

Safe: Mustard containing no salt or explicitly stating "non-iodized salt." Homemade mustard is the safest option as you control the ingredients completely.
Caution: Products listing simply "salt" or containing ingredients you can't verify. For example, some kosher salts are not iodized, but you must check the specific brand.
Unsafe: Any product containing iodized salt or sea salt.

Goitrogens and Mustard: Should You Worry?

Mustard greens and seeds are part of the cruciferous vegetable family, which contains compounds called goitrogens. In very large, raw quantities, goitrogens can interfere with the thyroid's ability to use iodine. However, for a short-term, low-iodine diet, this is typically not a major concern.

Cooking Reduces Risk: The enzymes that produce active goitrogens are largely deactivated by heat. Since commercial mustard is processed, the goitrogenic risk is minimized.
Quantity Matters: The amount of mustard consumed as a condiment is typically very small. The goitrogenic effect is linked to excessive, long-term consumption, especially in raw forms.
Main Focus: The primary goal of the LID is to reduce iodine, not goitrogens. Focusing on avoiding iodized salt, dairy, and seafood is far more important.

Navigating Condiments: Mustard and Alternatives

When following a low-iodine diet, your options for flavor don't have to be limited to just plain mustard. Here is a list of other condiments and sauces to consider:

Allowed:
- Homemade sauces and dressings using non-iodized salt.
- Pure spices and herbs.
- Vinegars (such as apple cider vinegar, white vinegar).
- Unsulfured molasses.
Limited:
- Tomato paste, ketchup, BBQ sauce, and other canned sauces can be allowed in small amounts (e.g., 1 tablespoon per day), provided they are salt-free or checked for non-iodized salt.
Avoid:
- Soy sauce and other soy-based sauces.
- Milk- or cream-based sauces.
- Commercial dressings with unverified ingredients.
- Worcestershire sauce.

Comparison Table: Common Mustards on a Low Iodine Diet


Mustard Type	Safety on LID	Key Consideration
Plain Yellow Mustard (Commercial)	Usually Safe	Check label for "non-iodized salt." Small amounts are fine.
Homemade Mustard	Safest	Complete control over ingredients, ensuring non-iodized salt and no iodine additives.
Dijon Mustard (Commercial)	Proceed with Caution	Often contains white wine and different salts. Check labels thoroughly for "salt".
Honey Mustard (Commercial)	Avoid	Frequently contains high-iodine ingredients like egg yolks or dairy. Best to make from scratch.
Spicy Brown Mustard (Commercial)	Usually Safe	Similar to yellow mustard, main concern is salt type. Read labels carefully.

How to Choose Safe Mustard

Making a safe choice requires a proactive approach. Here’s a simple checklist to follow before adding mustard to your low-iodine diet:

Check the label: Look specifically for the word "salt" in the ingredient list. If it simply says "salt" without specifying non-iodized, it's safer to avoid it.
Review the full ingredient list: Watch out for common iodine-containing additives like algin, carrageenan, or ingredients derived from dairy or eggs.
Opt for homemade: If you are a fan of mustard and have the time, making your own using a simple recipe with non-iodized salt guarantees your control over the iodine content.
Confirm with your doctor: If in doubt, especially with specialty or gourmet mustards, consult your physician or dietitian to confirm the ingredient list is compliant.

Conclusion: The Bottom Line on Mustard

Plain mustard is typically an acceptable condiment for a low-iodine diet. The most critical step is to read ingredient labels and verify that the product does not contain iodized salt, dairy, or other high-iodine additives. Homemade mustard offers the greatest peace of mind. By exercising a little caution and following the guidelines, you can continue to enjoy mustard while adhering to your low-iodine restrictions. For more resources on managing your diet during RAI treatment, consider consulting the Thyroid Cancer Survivors' Association, Inc..

Frequently Asked Questions

Plain yellow mustard contains a very low amount of iodine. The primary concern is the type of salt used in commercial production, which may be iodized.

You should proceed with caution with Dijon mustard. It often includes white wine and specific salts. Always check the label for non-iodized ingredients or opt for a homemade version.

No, not all brands are safe. You must check the ingredients list for each brand, focusing on the type of salt and presence of any high-iodine additives like dairy or certain colorings.

Mustard seed powder is not inherently high in iodine. However, it's important to be mindful of its goitrogenic properties, especially if consumed raw in large amounts. The small quantities used in condiments are generally fine for a LID.

Homemade mustard made with non-iodized salt is the safest option because you have complete control over the ingredients. Plain yellow or spicy brown mustard from a trusted brand with transparent ingredients is a good commercial alternative.

It is not recommended to use condiments at restaurants or fast-food establishments, as you cannot verify the ingredients, especially the type of salt used.

Commercial honey mustard is generally not recommended as it often contains egg yolks, which are prohibited on a low-iodine diet. You can make a homemade, compliant version using egg whites and non-iodized ingredients.