Is Diet Coke® or Coke Zero™ Keto-Friendly?—Soda on Keto

author avatar Dr. Eric Berg 08/31/2023

Is Coke Zero Keto? Both Diet Coke® and Coke Zero™ contain zero sugar, zero carbs, and zero calories—but are they keto-friendly? 

Technically speaking, any food product without carbs is considered keto-friendly. However, certain ingredients in Diet Coke are bad for your health—and they can also spike insulin!

Many of the health benefits associated with a keto diet are largely due to its role in preventing insulin spikes. If you’re consuming a food or beverage that doesn’t contain carbs but still spikes insulin, then that food is not keto-friendly. 

Let’s take a look at these two popular diet Coca-Cola sodas to see how they stack up and if Coke Zero is really keto. 

Coca-Cola zero sugar

Is diet soda keto-friendly? 

Diet soda can be keto-friendly, but it depends on the ingredients. Diet Coke and Coke Zero contain carbonated water and caffeine as well as the following ingredients: caramel color, phosphoric acid, aspartame, potassium benzoate, and citric acid. 

In addition to these ingredients, Coke Zero also contains potassium citrates, acesulfame potassium, and natural flavors.

Although these sodas contain zero net carbs, the aspartame in these beverages will spike insulin. Look for diet sodas without artificial sweeteners and without harmful ingredients.

Should you drink Diet Coke or Coke Zero on Healthy Keto®?

Diet Coke and Coke Zero contain several problematic ingredients, which make them a poor choice for Healthy Keto. 

Caramel coloring is made by heating sugar, typically from GMO corn, with an ammonia compound to create caramelization. The end product creates sticky proteins that can travel through your arteries to your brain, pancreas, liver, and kidneys.

Although Diet Coke and Coke Zero contain zero carbs and zero sugar, you still may experience complications associated with insulin resistance because of the added artificial sweetener aspartame.

In conclusion, Coke Zero and Diet Coke should not be consumed on Healthy Keto!

Best and worst sweeteners on keto 

Artificial sweeteners like aspartame affect the gut microbiome and promote insulin resistance. Aspartame can even raise blood sugar just as much as regular sugar! This means that aspartame will not prevent weight gain and is not suitable for a keto diet. 

This study published by Environmental Health classifies aspartame as a chemical carcinogen in rats that has the potential to cause cancer in the offspring of rats exposed prenatally. 

The study concluded the following: “These new findings confirm that aspartame is a chemical carcinogen in rodents. They confirm the very worrisome finding that prenatal exposure to aspartame increases cancer risk in rodent offspring”

You’ll also want to avoid saccharin and sucralose. Similar to aspartame, these artificial sweeteners are linked to fluid retention, insulin resistance, and damage to the gut.

Avoid the sugar alcohol maltitol—with a glycemic index of 52, it raises blood sugar almost as much as table sugar!

Look for keto-friendly sugar substitutes like monk fruit and stevia. Monk fruit and stevia are both naturally derived and have a 0 glycemic index, so they will not spike insulin. 

You can also try keto-friendly sugar alcohols like erythritol and xylitol. Be sure to choose organic or non-GMO. 

Erythritol has a cold sweetness and a glycemic index of 0. Xylitol is popular because its taste is very similar to table sugar, but it has a glycemic index of 13.

Sugar alcohols can sometimes cause digestive upset, especially when consumed in high amounts.

keto-friendly drink

Healthy Keto soda alternatives

If you want to enjoy a diet drink or diet soda on a keto diet, choose a carb-free beverage without caramel color and caramel flavoring. Look for diet drinks without phosphoric acid and without artificial sweeteners like aspartame. 

Carbonated or sparkling water is an excellent option if you’re on a low-carb diet. You can even add lemon and stevia to carbonated water for a homemade keto-friendly drink.

Woman rejecting coke zero sugar-free

Key takeaways

Coke Zero and Diet Coke contain several unhealthy ingredients and are best avoided on a keto diet. Choose beverages like sparkling mineral water or sodas sweetened with keto-friendly sweeteners rather than artificial sweeteners.

The question “is Coke Zero keto” might not be the best question.

When choosing a keto-friendly beverage, consider all of the ingredients, not just the carb content. Focus on removing carcinogenic ingredients from your diet to get healthy and then lose weight, not vice versa!


1. Is Diet Coke or Coke Zero better for keto?

Diet Coke and Coke Zero are two very similar sodas made by Coca-Cola. Zero sugar, zero calories, and zero carbs are their claim to fame.

Diet Coke and Coke Zero both contain aspartame which can spike insulin. In order to stay in ketosis, you want to avoid spiking insulin, so neither Diet Coke nor Coke Zero are suitable for a keto diet. 

2. Can I drink Diet Coke on keto?

No. Although Diet Coke has zero total carbs, it contains several unhealthy ingredients, including aspartame. 

3. Is Coke Zero keto?

Coke Zero contains zero sugar, but is Coke Zero keto? The answer is no! Coke Zero contains many unhealthy ingredients—and some may spike insulin and make it more difficult to stay in ketosis. 

4. Can I drink soda on Healthy Keto? 

You can drink club soda on Healthy Keto. You can also have drinks that are low in carbs and are sweetened with keto-friendly sweeteners like stevia, monk fruit, erythritol, or xylitol. 

5. What is the best soda to drink on keto?

Sparkling water is the best soda to drink on keto. If you want something sweet, stick to keto-friendly sugar substitutes like monk fruit, stevia, erythritol, and xylitol. 

6. Can I have soda made with stevia on keto? 

Yes! Be sure to check the other ingredients to make sure there aren’t any artificial sweeteners, caramel color, or other unwanted ingredients. 

7. Can I drink sparkling water on keto? 

Yes! Sparkling water is a great alternative to soda on a keto diet. 

8. Will diet soda kick me out of ketosis?

If the diet soda contains aspartame, it will spike insulin, which may kick you out of ketosis. Look for diet drinks made with keto-friendly sugar alternatives.


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