Red licorice candy like Twizzlers and Red Vines is not a direct threat to your kidneys in the way that real licorice is. Most red licorice products contain no actual licorice root extract and none of the compound, glycyrrhizin, that makes black licorice genuinely dangerous for kidney function. That said, red licorice is still a high-sugar candy, and eating a lot of it over time can contribute to kidney problems through less obvious routes.
Red Licorice Usually Isn’t Real Licorice
This is the most important thing to understand. Despite the name, popular red licorice brands are flavored with strawberry, cherry, or other fruit flavoring rather than licorice root. The active compound in real licorice, glycyrrhizin, is what causes serious kidney and cardiovascular problems. If your red licorice doesn’t list “licorice extract” or “glycyrrhizin” on the ingredients label, it doesn’t carry those specific risks.
Black licorice, on the other hand, often does contain glycyrrhizin and is a genuinely different product when it comes to kidney health. If you eat both types, it’s worth checking the label on any black or European-style licorice you buy.
How Real Licorice Damages the Kidneys
Glycyrrhizin interferes with an enzyme system in the kidneys that normally converts cortisol into an inactive form. When that enzyme is blocked, cortisol builds up in the kidneys and starts activating the same receptors that aldosterone uses to regulate sodium and potassium balance. The result is a state that mimics having too much aldosterone: your body retains sodium and water while dumping potassium.
This potassium loss, called hypokalemia, is the most dangerous consequence. Case reports describe patients with potassium levels dropping to 1.8 mmol/L from chronic licorice use, well below the normal range of 3.5 to 5.0. Potassium that low affects the heart, skeletal muscles, and intestines. Symptoms include muscle weakness, paralysis, constipation, dangerous heart rhythms, and in rare cases cardiac arrest. Some patients with severe licorice-induced hypokalemia had no symptoms at all until they were tested, which makes it particularly deceptive.
The good news is that these effects are reversible. Studies show that after stopping licorice, the renin-aldosterone system returns to normal within two to four months. But during active use, the suppression of the kidney enzyme can persist as long as glycyrrhizin’s breakdown products remain in the body.
How Much Glycyrrhizin Is Too Much
The European Union’s Scientific Committee on Food set an upper limit of 100 mg of glycyrrhizin per day, which corresponds to roughly 60 to 70 grams of real licorice candy. The Dutch Nutrition Information Bureau uses a more generous limit of 200 mg per day, roughly 150 grams of candy. A more conservative estimate from a 1994 study suggested that 1 to 10 mg per day is safe for most healthy adults, corresponding to just 1 to 5 grams of actual licorice.
The FDA classifies licorice and its derivatives as “generally recognized as safe” for use in foods but does not set a strict daily consumption cap. The agency assumes that glycyrrhizin levels in commercially sold foods won’t cause harm as long as people don’t consume them in excess. That’s a somewhat vague standard, which is why some researchers have called for clearer warning labels on licorice products.
None of these limits apply to red licorice that contains no glycyrrhizin. But if you eat a product labeled “licorice” that actually contains licorice root, these thresholds matter.
The Sugar Problem in Red Licorice
Where red licorice does pose a kidney-relevant risk is through its sugar content. A serving of Red Vines (three twists) contains 12 grams of added sugar, which is 24% of the recommended daily value. It’s easy to eat far more than three pieces in a sitting, and a full bag can deliver several days’ worth of added sugar at once.
A large analysis of U.S. adults using national nutrition survey data found that higher added sugar intake was significantly associated with a greater prevalence of kidney stones. People in the highest sugar intake group (25% or more of daily calories from added sugar) had 88% higher odds of kidney stones compared to those who kept added sugar below 5% of calories. Fructose intake specifically has been linked to increased kidney stone risk as an independent factor.
High sugar consumption also drives obesity, type 2 diabetes, and cardiovascular disease, all of which are major risk factors for chronic kidney disease. The kidney damage from sugar isn’t dramatic or sudden the way glycyrrhizin toxicity can be. It’s the slow, cumulative kind that builds over years of excess intake.
What About Red Dye?
Red licorice typically contains Red 40, the most widely used artificial food dye in the U.S. Some animal research has raised concerns. One study in rats found that Red 40 combined with another dye caused oxidative stress and signs of toxicity in both the liver and kidneys. A mouse study found that Red 40 added to a high-fat diet led to changes in organ size, including the kidneys, along with colonic inflammation and DNA damage.
These findings are preliminary and come from animal models using controlled doses over extended periods. There’s no strong clinical evidence that Red 40 at the levels found in candy causes kidney damage in humans. But the research is limited enough that it’s not possible to rule out long-term effects entirely, particularly for people who consume large amounts of dyed foods regularly.
Who Should Be Most Careful
If you have existing kidney disease, high blood pressure, or low potassium levels, both real and red licorice deserve some caution. Real licorice (black) is the more urgent concern because glycyrrhizin directly disrupts the kidney’s handling of sodium and potassium. Even small amounts can worsen blood pressure and potassium balance in people whose kidneys are already compromised.
Red licorice poses a more generic risk as a high-sugar, nutritionally empty candy. If you’re managing kidney stones, diabetes, or chronic kidney disease, the sugar load matters more than anything else in the product. An occasional handful is unlikely to cause problems, but regular, heavy consumption adds up in ways that strain kidney health over time.