Benzoic acid, vitamin C and possible benzene in kidney disease
What it found
In people with kidney disease, vitamin C levels are often low, and the authors suggest that benzoic acid from food may react with vitamin C to form benzene.
This has been shown in lab tests and some animal work, but not yet in people.
What they found
Studies in people
Vitamin C levels in kidney disease
People with chronic kidney disease often have low vitamin C levels, and levels drop further with dialysis. For example, one study found that 80% of patients with stage 4-5 CKD had inadequate levels, and another found 79% were deficient.
Benzene health effects
Benzene is a known human carcinogen. It can cause blood disorders like anemia and leukemia, and even low long-term exposure is linked to higher risk of death from cardiovascular disease and cancer.
Kidney disease and benzoic acid
People with kidney disease may clear benzoic acid more slowly, which could lead to higher levels in the body. However, there is no consistent evidence that benzoic acid or benzene levels are higher in this group.
Animal and lab studies
Benzene formation in lab tests
In drinks and lab experiments, benzoic acid can react with vitamin C to form benzene, especially with heat, light, or metal ions. This happens at acidic pH, like in soft drinks.
Benzene formation in animals
A mid-20th century animal study found that giving benzoic acid compounds to rats depleted vitamin C in their adrenal glands. This suggests a possible reaction in the body, but it does not prove benzene was formed.
Other findings
Benzoic acid exposure
Benzoic acid is a widely used preservative in soft drinks, juices, and pickles. Average intake varies by country, but high consumers can reach 7.3 to 14 mg per kg body weight per day.
What the authors conclude
“Given the widespread use of benzoic acid as a food preservative and the ongoing discussion around vitamin C supplementation in patients with kidney disease, this review invites further investigation to evaluate whether this reaction represents a health hazard for this population.”
Also in their conclusions
- They conclude that it is not yet known whether this reaction happens in the body and call for more research.
- They are planning a study in kidney transplant recipients to see if a benzoic acid-free diet changes vitamin C levels or benzene markers.
- They say that clarifying the risk of benzene exposure in people with reduced kidney function is critical.
How it was done
The authors noticed that people with kidney disease have lower vitamin C levels than expected, even though vitamin C is normally removed by the kidneys. They wanted to explore whether this could be linked to benzoic acid, a common food preservative, and whether the two could react in the body to make benzene.
The authors searched medical databases for studies on vitamin C, benzoic acid, and benzene in people with kidney disease, kidney transplant recipients, and in lab or animal experiments. They also looked at guidelines and regulatory reports. They combined the findings in a narrative review.
What it can’t tell you
- This is a review of other studies, not a new experiment. It cannot prove that benzoic acid and vitamin C react to form benzene in people.
- The animal and lab findings may not apply to humans. The authors note that no controlled human studies have yet tested this.
- The review cannot say how much benzene, if any, might be formed in the body from food preservatives.
Who paid
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- University of Groningen, The Netherlands; Erasmus Medical Centre, The Netherlands
The paper
- Title
- Vitamin C and Benzoic Acid Intake in Patients with Kidney Disease: Is There Risk of Benzene Exposure?
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Yepes-Calderón M, Doorenbos CSE, Corpeleijn E, et al (2025). Vitamin C and Benzoic Acid Intake in Patients with Kidney Disease: Is There Risk of Benzene Exposure?. Nutrients. doi:10.3390/nu18010132Free full textPubMed 41515248DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error