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The Impact of Diet Soda on Blood Sugar Levels

Monica McCafferty, MS, CNS

Published in Nutrition

8 min read

September 15, 2022
December 1, 2023
A closeup of a hand holding a can of Diet Coca Cola
A closeup of a hand holding a can of Diet Coca Cola

Are you a Diet Coke lover? For the last several decades, diet sodas have been popularized as a “healthier option” to normal sodas that are known to be high in sugar and calories.

But in recent years, researchers have been debating the long-term health effects of these drinks. Despite being sugar-free and often low in calories, there are other ingredients found in diet drinks and sodas that may pose certain health risks.

In this article, we’ll explain why diet drinks were invented in the first place, then take a critical look at the research around these drinks.

History of Diet Drinks

While the invention of some sodas can be dated all the way back to the 1800s, diet drinks are a comparatively new creation. Diet drinks were initially invented for people with diabetes and first became available in the 1950s.

In 1952, Hyman Kirsch and Morris Kirsch of the Kirsch Bottling Company of Boston first created a sugar-free ginger ale. However, its consumption soon enough expanded beyond the diabetic population.

Dr. Pepper released their own sugar-free, diet beverage in the early 1960s with Coca cola following suit a year later. In the late 1990s, Coca Cola was popularized in diet culture by models who followed Diet Coke-and-cigarette diets.

While it was ultimately damaging to these women’s health, mainstream media glamorized this image and made these drinks a staple in many people’s diets which remains popular today.

Now that we know a little more about their origins, let’s take a look at how diet sodas can affect your body.

Ingredients in Diet Drinks

a jar of sugar

Artificial Sweeteners

The first sweetener to be used in diet sodas was cyclamates, but was subsequently banned due to research showing a link between this sweetener and cancer. Since then, companies have used a variety of different sugar-free substitutes such as:

  • Aspartame 
  • Stevia 
  • Saccharin 
  • Sucralose (also known as acesulfame-k) 

While artificial sweeteners were originally used as a healthier alternative, the research on whether they actually are healthier is conflicting.

Bariatric surgeon Dr. Kevin Huffman says, "diet sodas carry their own health risks—potential links exist between artificial sweeteners and alterations in gut bacteria; an increased preference for sweetness; even metabolic shifts possibly impacting insulin sensitivity."

A study published this year found that artificial sweeteners, such as the ones found in diet sodas, may affect the gut microbiome and affect glycemic control. Other research shows a link between artificial sweeteners and an increased risk of metabolic dysfunction such as type 2 diabetes and metabolic syndrome.

Aspartame, specifically, has long been considered an unsafe sweetener. A 2006 study done in rats found aspartame to increase risk of specific cancers such as leukemias, lymphomas, and cell carcinomas in certain parts of the pelvic and urinary tract.

However, multiple studies that have since investigated the safety of aspartame in rats seem to have determined this sugar-free sweetener to be non-carcinogenic. Aspartame remains as the primary sweetener in Diet Coke and Coke Zero.

Carbonated Water

Another major component of diet drinks (and sodas in general) is carbonated water. There is some research that suggests carbonated water can interfere with some metabolic processes but this research is limited and weak.

One small study done in rats, for example, found that carbonated water can increase levels of ghrelin, the hunger hormone. The authors of this study explained this increase was due to the presence of carbon dioxide in the water.

However, research done on rats or mice doesn’t always correlate with the research done with human participants. For example, a 2017 study done with female participants found that the carbon dioxide in carbonated water (or beverages) actually promoted feelings of satiety.

Because of this, more research is needed to determine the health effects of carbonated water on human health.


pouring a glass of coca cola

The most common color dyes used in diet sodas include:

  • Caramel color 
  • Yellow-5 
  • Blue #1

Unlike the effects of sweeteners and carbon dioxide, the health consequences of consuming color dyes is well documented in research. One review found that all nine US-approved color dyes, including the ones listed above, are cause for alarm where health is concerned.

This review found yellow-5 to be contaminated with carcinogenic compounds such as benzidine, which can cause hypersensitivity reactions. It has also consistently tested positive for genotoxicity (or the ability of certain chemicals to cause damage to genes).

Blue #1 may also cause hypersensitivity reactions, and research shows that caramel food coloring contains a chemical known as 4-mel, which may be carcinogenic.

An important factor in how harmful these dyes can be is the dosage and frequency at which they are consumed, meaning excessive consumption may lead to a higher risk of cancer development. However, the International Agency for Research on Cancer cites the evidence as insufficient at this time.


Some diet sodas contain small amounts of caffeine. In moderate doses, caffeine has some health benefits, which may include decreased fatigue, increased alertness, and decreased feelings of depression.

For context, an average cup of brewed coffee can contain around 100 milligrams of caffeine. An independent analysis listed the caffeine content of other diet sodas as follows:

diet soda caffeine content graphic


A couple of the more common preservatives used in diet sodas include phosphoric acid and potassium benzoate. These preservatives may interfere with levels of certain vitamins and minerals within your body.

For example, research has shown that consuming sodas with phosphoric acid can be a risk factor for hypocalcemia, or extremely low levels of calcium, in women who are postmenopausal. Potassium benzoate has been linked to problems with eye development in mice, though more research is needed to determine the effects in humans.

What Potential Health Effects Can Diet Drinks Have?

Some of the ingredients, such as the artificial sweeteners found in diet drinks, can have potentially negative health consequences. Let’s take a closer look at the research.

High Blood Sugar

As we’ve touched upon already, there is some research suggesting a link between diet drinks and high blood sugar. This may seem ironic to some, considering that these drinks are marketed as sugar-free alternatives, which, in theory, should help promote healthy blood sugar levels.

Additional research has found that sugary beverages are an important factor in the development of type 2 diabetes. However, switching to diet sodas may not decrease the risk of developing type 2 diabetes. Researchers assert that more research is still needed to determine how diet soda can affect glycemic control.

Weight Gain

someone standing on a scale

While some people choose sugar-free diet sodas when trying to lose weight, this alternative may actually hinder your weight loss goals. In fact, Qing Yang’s review in the Yale Journal of Biology and Medicine illustrates that artificial sweetener consumption is positively associated with weight gain.

This conclusion comes from an analysis of several large scale studies that found that consuming artificial sweeteners lead to higher BMI when following up with participants. If you have weight loss goals, staying hydrated by drinking plenty of water may be a better option.

Kidney Disease

Similar to the controversy between type 2 diabetes and artificially sweetened sodas, the link between these beverages and kidney disease has yet to be deeply explored. However, one study did indicate that high consumption of artificially sweetened soda may increase the risk of kidney disease.

The researchers of this study found that consuming two or more servings of diet sodas leads to a twofold increase in kidney function decline in women. More research is needed to determine how these sweetened beverages affect the kidneys.

Cardiovascular Disease

a woman holding her chest in pain

Along with affecting kidney function, diet sodas may affect your cardiovascular health over time. Dr. Ila Dayananda shares, "some research has suggested potential associations between regular consumption of diet sodas and health conditions like obesity, metabolic syndrome, type 2 diabetes, cardiovascular disease, and stroke, but more research is needed to establish causation and better understand these relationships."

One such study found that two or more diet sodas a day can lead to a higher risk of cardiovascular events, and increase risk of both cardiovascular mortality and overall mortality. While this study was done in postmenopausal women, it’s interesting to note that these women did not have a pre-exisitng risk.

This suggests that regular consumption of diet sodas alone may be significant enough to create cardiovascular health risks (although this may not be the case for everyone).


Interestingly, diet soda consumption can have a negative effect on mood. However, this finding is in direct contrast to research suggesting that caffeine, which is present in most diet sodas, can have a positive effect on mood.

One explanation for this may be that the lower mood caused by diet soda was found in those who consumed soda excessively (more than four cans of soda) whereas the positive effect of caffeine on mood only may only apply in moderate doses.


Three Healthy Alternatives to Diet Drinks

Diet sodas can be a controversial topic, be it from the lens of diet culture or the other long term consequences they have on your health. If you’re looking for healthier alternatives to both regular and diet sodas, look no further! Here are three refreshing drinks to try out this season.

Fruit Infused Sparkling Water by Darn Good Veggies

three glasses of fruit infused water

This recipe includes options for different flavors (including mangoes). Here’s a cucumber infused version that’s low in sugar and more helpful for healthy blood glucose levels.


  • 1 (12) ounce can sparkling water
  • 1 ½ tablespoons cucumber juice
  • Tiny squeeze lemon (optional, but it really brings out the flavor)

Iced Tea

Iced tea is a refreshing drink that’s quick and easy to make at home! Here’s how to make one in a few simple steps.


  • Tea bag of your choice (rooibos is a good to go for the classic iced tea experience)
  • Ice
  • Water


  • Steep your tea in water according to packet instructions
  • Let tea sit and cool for up to 10 minutes 
  • When it’s done cooling, pour ice into a glass 
  • Top up glass with steeped tea
  • Enjoy!

Strawberry Coconut Water Lemonade by Iowa Girl Eats

glasses of coconut water

This recipe puts a fresh twist to your typical coconut water by adding in fresh fruit and sparkling water. If you’re looking for a cool drink to enjoy in the last few weeks of warmer weather, try this drink out.


  • 1/2 cup water
  • 1/2 cup sugar
  • 3/4 cup fresh-squeezed lemon juice (~4 lemons)
  • 1 pound strawberries, trimmed and halved
  • 2 cups coconut water 
  • Sparkling water (optional)
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Heather Davis, MS, RDN, LDN

Reviewed by: Heather Davis, MS, RDN, LDN

Heather is a Registered and Licensed Dietitian Nutritionist (RDN, LDN), subject matter expert, and technical writer, with a master's degree in nutrition science from Bastyr University. She has a specialty in neuroendocrinology and has been working in the field of nutrition—including nutrition research, education, medical writing, and clinical integrative and functional nutrition—for over 15 years.

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