Diet Coke contains no sugar and has little direct impact on blood sugar. Still, drinking it too often may carry potential health risks.
Diet soda contains aspartame and other artificial sweeteners. These sweeteners are virtually free of calories and carbohydrates, so they don’t cause the same blood sugar spikes as regular soda. However, research on the use of artificial sweeteners for blood sugar management is mixed.
Many studies show that sweeteners like aspartame and sucralose don’t cause major changes in blood sugar or insulin levels. But other research suggests these sweeteners could still affect how your body processes glucose or responds to insulin over time.
A 2020 study in people with type 2 diabetes found higher insulin resistance among people who regularly ate artificial sweeteners compared to people who did not. Insulin resistance occurs when your body’s cells don’t respond properly to insulin. This makes it harder to keep blood sugar levels in a healthy range.
Evidence on the long-term health effects of artificial sweeteners in diet soda remains limited. Some research suggests potential links to certain health risks, such as:
- Worsened mental health: Artificial sweeteners have been linked to irritable moods and increased risk for mental health conditions like depression.
- Faster cognitive decline: Over time, regularly eating artificial sweeteners may affect your cognition. A large 2025 study linked long-term use of artificial sweeteners like aspartame to an increased rate of cognitive decline.
- Higher risk of heart disease: Some studies suggest that high intake of artificial sweeteners may increase the risk of heart disease.
- Weight gain: Some research has linked artificial sweeteners to weight gain, though others have found no association.
- Increased cancer risk: The World Health Organization’s International Agency for Research on Cancer (IARC) has classified aspartame as “possibly carcinogenic to humans” (Group 2B). However, the U.S. Food and Drug Administration (FDA) states that current evidence does not support a link between aspartame and cancer in humans.
- Diabetes complications: Worsening diabetic eye disease (retinopathy) and higher A1C levels have been observed in some people who regularly consume artificial sweeteners.
The FDA considers artificial sweeteners typically found in Diet Coke safe for most people when used in moderation.
For context, a 130-pound person would need more than 75 packets of Equal® or 23 packets of Splenda® in one day to exceed current recommended limits.
Indirect Effects
Beyond blood sugar, diet soda may also affect gut health. Some studies suggest artificial sweeteners can alter the balance of gut bacteria. This may influence how your body manages sugar. It may also trigger cravings for real sugar, even though it doesn’t contain any itself.
A study found that cutting back on artificial sweeteners reduced sugar cravings in as little as one week.
Artificial sweeteners in diet soda are considered safe by the FDA when consumed within recommended limits. If you’re concerned about potential health effects, enjoy diet soda occasionally as part of a balanced diet. When possible, opt for water, sparkling water, or unsweetened tea instead.
