What Soda Can I Have on a Low Iodine Diet?

January 14, 2026 •

4 min read

According to Memorial Sloan Kettering Cancer Center, most sodas, including regular and diet varieties, are acceptable on a low iodine diet, with one major exception: those containing Red Dye #3. A low iodine diet is crucial for preparing the body for radioactive iodine treatment by making thyroid cells more receptive to the therapy.

Quick Summary

Most carbonated soft drinks are generally permissible, but you must check labels to confirm no Red Dye #3 is present. Look for clear or non-red colored sodas and avoid any product with unlisted or unknown ingredients.

Key Points

Check Labels for Red Dye #3: The primary ingredient to avoid in soda on a low iodine diet is Red Dye #3 (erythrosine), which contains high levels of iodine.
Most Colas are Safe: Standard cola drinks are typically safe as their brown coloring is not derived from Red Dye #3.
Clear Sodas are Usually Fine: Lemon-lime and ginger ale sodas are typically clear and therefore safe for consumption.
Exercise Caution with Orange and Red Sodas: Orange, red, pink, or purple sodas are more likely to contain Red Dye #3 and should be carefully checked or avoided.
Avoid Restaurant Sodas: It's difficult to verify ingredients in restaurant or fast-food beverages, so bottled or canned sodas are the safest option.
Explore Other Options: Don't forget other safe drinks like water, fruit juice (without red dye), and black coffee or tea.

Understanding the Low Iodine Diet and Soda

A low iodine diet is a temporary, doctor-supervised eating plan typically prescribed for patients preparing for radioactive iodine (RAI) therapy for thyroid cancer or hyperthyroidism. The goal is to deplete the body's natural iodine stores, ensuring that any remaining thyroid cells are "hungry" for iodine, thus maximizing the absorption of the radioactive treatment. While the diet primarily focuses on avoiding high-iodine foods like seafood, dairy, and iodized salt, it's also important to be mindful of beverage choices. For many people, soda is a daily part of their routine, and understanding which ones are safe is key to adherence.

The Key Ingredient to Avoid: Red Dye #3

The primary concern with soda on a low iodine diet isn't the carbonation or sugar, but specific food coloring, especially Red Dye #3 (erythrosine). This additive, though not common in all soft drinks, is high in iodine and must be avoided. The good news is that most major cola and lemon-lime brands do not contain this dye. However, it is essential to check the ingredient label of any red-colored soda, including certain varieties of fruit punch, some flavored lemon-lime, or any specialty red-colored soft drinks. The simplest rule is: when in doubt, check the label, or opt for a clear or brown-colored soda.

Comparing Safe vs. Unsafe Soda Choices

To make navigating the grocery store easier, here is a helpful comparison table of common soda types. Remember to always verify the specific brand and flavor you are purchasing.


Soda Type	Low Iodine Status	Common Brands	Important Notes
Colas	Generally Safe	Coca-Cola, Pepsi, Diet Coke	Standard versions are fine. Always check flavored or specialty editions.
Lemon-Lime Sodas	Generally Safe	7-Up, Sprite, Sierra Mist	Most are clear and safe. Be cautious of colored or special-edition flavors.
Ginger Ale	Generally Safe	Schweppes, Canada Dry	A safe and often soothing choice.
Root Beer	Generally Safe	A&W, Mug Root Beer	Typically colored brown, not with Red Dye #3.
Orange Sodas	Check Label	Fanta, Sunkist	Some brands or flavors may use Red Dye #3, so check every time.
Red Cream Sodas	Avoid (Potential)	Big Red, Barq's Red Cream Soda	Often contain Red Dye #3, so it's safest to avoid.
Fruity Sodas	Check Label	Various brands	Any red, pink, or purple varieties are highly suspect and require label scrutiny.

Beyond Soda: Other Safe Low Iodine Beverages

While soda can be a relief, variety is important during this temporary diet. Fortunately, there are many other excellent low iodine beverage options to keep you hydrated and satisfied.

Water: Tap water and bottled water are excellent choices and are perfectly safe. You do not need to drink distilled water unless otherwise instructed.
Fruit Juices: Most fruit juices are fine, but be sure to avoid those containing Red Dye #3 or maraschino cherries. Homemade fruit juice is a safe option.
Coffee and Tea: These are allowed, but they must be consumed black. Avoid milk, creamer, or any dairy additives, as dairy is high in iodine.
Carbonated Water: Plain or flavored carbonated water and seltzer are great, safe options for a bubbly treat.
Nondairy Milks: Opt for non-dairy alternatives like almond, rice, or oat milk, but carefully read the labels to ensure no potassium iodide or carrageenan has been added.

Common Pitfalls and Tips for Success

One of the biggest challenges on a low iodine diet is the presence of hidden iodine in processed foods and drinks. Restaurant and fast-food sodas should be approached with caution, as it can be difficult to verify ingredients. When dining out, it is safest to stick to water or a plain, clear soda from a can or bottle where you can control and read the label.

Tips for success include:

Plan Ahead: Before going out or shopping, make a list of approved sodas to avoid impulsive purchases.
Read All Labels: Ingredient lists are your most important tool. Look for Red Dye #3, erythrosine, and any unlisted additives.
Stay Hydrated: The diet can feel restrictive, so make sure you are still drinking plenty of fluids, with water as your primary choice.
Homemade is Safest: If you enjoy fruit-flavored drinks, consider making your own with fresh fruits and safe sweeteners to eliminate any doubt.

Conclusion

Navigating a low iodine diet requires careful attention to detail, but it doesn't mean you have to give up all your favorite beverages. While many sodas are safe, the most important rule is to avoid any drink that contains Red Dye #3. By being a vigilant label reader and focusing on clear or brown-colored options, you can safely enjoy a carbonated treat while successfully preparing for your medical treatment. Always consult with your healthcare provider for personalized dietary guidelines and to ensure your choices align with your specific treatment plan.

Frequently Asked Questions

Yes, diet soda is generally allowed on a low iodine diet, as long as it does not contain the red dye known as Red Dye #3 (erythrosine). Always check the ingredient label to be certain.

Red Dye #3 is a food coloring agent that contains iodine. Consuming it adds to the body's iodine levels, which can interfere with the effectiveness of radioactive iodine (RAI) treatment.

Yes, root beer is typically safe for consumption on a low iodine diet. Its brown color is not a result of iodine-containing Red Dye #3.

Don't panic if you accidentally consume a small amount of a restricted item. The low iodine diet is about reducing overall intake, not eliminating every trace. The most important thing is to continue following the diet as closely as possible for the remainder of the preparation period.

No, fruit juices or fruit punch with red coloring should be avoided, as they may also contain Red Dye #3. It's best to stick to clear or naturally colored fruit juices, or make your own from fresh fruit.

Yes, most flavored sparkling waters are safe, but it is always wise to check the ingredients list. Plain or natural flavors are safest, but some brands might use coloring or additives to be aware of.

While not all food dyes contain iodine, it is best to avoid any brightly colored sodas, especially reds and oranges, to be safe. Opting for naturally colored or clear beverages eliminates the risk entirely.