Too much fructose damages the kidneys
Nephrologists warn against hidden sugar in drinks and ready-made products
Advertisement
Excessive consumption of fructose (fruit sugar) can cause lasting damage to the kidneys and increase the risk of chronic kidney disease (CKD). Fructose, which is added industrially in large quantities, is particularly problematic - for example in soft drinks, energy drinks, fruit juices and numerous ready-made products, often in the form of fructose-glucose syrup or corn syrup. The German Society of Nephrology (DGfN) points this out on the occasion of World Kidney Day on March 12, 2026.
"Fructose is not a 'healthier' sugar - on the contrary: in large quantities, it can have a massive impact on the kidneys via various metabolic pathways," emphasizes the DGfN. The consumption of sugary drinks is particularly critical, as fructose is absorbed quickly and in high concentrations. In combination with heat and a lack of fluids - for example in summer or during physical exertion - this can put additional strain on the kidneys.
The DGfN therefore recommends consistently reducing sugar-sweetened drinks in everyday life and drinking water, unsweetened tea or coffee without sugar instead. At the same time, it calls on health policy-makers to follow the recommendations of the German Alliance for Non-Communicable Diseases (DANK), the German Medical Association and the German National Academy of Sciences Leopoldina to introduce a sugar tax.
How fructose affects the kidneys
Fructose is metabolized in the body mainly in the liver, but also in the kidneys, and differs fundamentally from glucose metabolism. High fructose consumption promotes the development of obesity, fatty liver and insulin resistance - key drivers of high blood pressure and type 2 diabetes. "Both diseases are among the most important risk factors for CKD," says Professor Dr. med. Sylvia Stracke, Head of Nephrology and Hypertensiology at the University Medical Center Greifswald and DGfN spokesperson. In addition, numerous studies show that high levels of fructose can increase uric acid levels. "Elevated uric acid is associated with high blood pressure, gout, kidney stones and inflammatory processes in the kidneys," says the nephrologist. At the same time, fructose promotes the formation of fat and inflammation in the body, which can also damage the fine blood vessels in the kidneys.
Mechanisms of kidney damage
From a nephrological point of view, several mechanisms are relevant:
- Uric acid production: fructose is the only sugar that leads to increased uric acid formation when it is broken down. A permanently elevated uric acid level is considered a major factor in kidney damage, kidney stones and inflammation.
- Inflammation and hardening of the kidney tissue (fibrosis): Long-term high fructose consumption promotes inflammatory processes and fibrosis.
- Energy consumption (ATP depletion): A lot of energy is consumed when fructose is broken down in the kidneys. This results in a lack of energy in the cells, which can trigger inflammation, oxidative stress, dysfunction of the inner wall of the blood vessels (endothelium) and a narrowing of the blood vessels.
- Indirect effects: Fructose promotes insulin resistance, high blood pressure and fatty liver - conditions that further worsen kidney function.
Consequences for kidney health
A permanently high consumption of sweetened drinks is associated with several health risks. Sylvia Stracke lists them:
- Increased risk of CKD
- Kidney stones, especially uric acid stones
- Albuminuria, i.e. the increased presence of protein in the urine as an early sign of kidney damage
- Particular risk in hot weather and dehydration, when sugary drinks do not compensate for the lack of fluids, but instead increase it
- Increased new fat formation and deposition both as subcutaneous fat and as so-called visceral fat.
Where fructose is everywhere - from energy drinks to children's yogurt
"It is not fructose from fresh fruit that is problematic, but above all the added fructose in industrially produced foods," explains the nephrologist. It can be found in, among other things:
- Soft drinks, energy drinks and sodas
- "Sports drinks", iced teas and flavored waters
- Fruit yogurts, breakfast cereals, muesli bars and desserts
- ready-made sauces, ketchup, dressings, baked goods and snacks.
"Many consumers underestimate how much fructose they consume through drinks alone. Half a liter of soft drink or energy drink can already contain more sugar than is recommended for adults per day," she warns.
Prevention: what everyone can do for their kidneys
Kidney disease often goes unnoticed for a long time. If you have your kidney values (eGFR, UACR), blood pressure and blood sugar checked regularly, you can take early countermeasures.
For kidney health, the DGfN recommends
- Quench your thirst with water instead of soft drinks or energy drinks
- Check ingredient lists and avoid fructose-glucose syrup, corn syrup or "fruit sugar" wherever possible
- Aim for and maintain a normal weight
- Treat obesity, high blood pressure and diabetes consistently.
"With a few, but consistently implemented behavioral changes, the personal risk of CKD can be significantly reduced," says Dr. Nicole Helmbold, Secretary General of the DGfN.
Calls for policy and care: Sugar brake and better early detection
In view of the increasing number of people with CKD, the DGfN is calling for effective health policy measures to reduce the sugar content in drinks and convenience products. These include clear nutritional labeling, binding reduction targets for added sugar and greater health education.
At the same time, the professional association supports the current political debates on tax incentives for high-sugar drinks. Stefan Schwartze, Member of the German Bundestag and Federal Government Commissioner for Patients' Affairs, explains: "I very much welcome the public debate that has been initiated on a sugar tax. Such a tax would benefit children and young people in particular - and therefore those who are unable to protect themselves due to a lack of knowledge and need our special care."
International data shows that measures work: In a global study of 107 countries (1), the daily consumption of sweet drinks among schoolchildren was lower in countries with sugar taxes than in countries without such levies. 32 countries already levy taxes on sweet drinks - with a measurable reduction in consumption.
At the same time, the early detection of kidney disease must be improved. Studies show that many patients only receive nephrological care at a late stage.
"Every kidney disease that is detected early is an opportunity to prevent dialysis and transplantation through behavioural change and therapy - we must not let this opportunity go to waste," emphasizes Nicole Helmbold.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
Original publication
Other news from the department science
