Chen Chien-jen Claims 'Drinking More Water Removes Benzo[a]pyrene' – Chang Chang-chuan Refutes: No Evidence That Hydration Reduces Toxicity

The carcinogenic oil scandal involving Zhonglian continues to escalate. Academia Sinica President Chen Chien-jen stated that drinking more water can remove benzo[a]pyrene (BaP), asserting that this applies to all carcinogens. In response, National Taiwan University public health professor Chang Chang-chuan posted on Facebook, pointing out that the 2017 U.S. Environmental Protection Agency (EPA) publication 'BaP Toxicological Assessment' does not indicate that increased water intake reduces human BaP toxicity. International recommendations for reducing BaP burden in the body generally emphasize minimizing BaP intake from other foods and reducing exposure via two pathways: respiration and skin contact. Additionally, adopting a diet rich in fruits, vegetables, legumes, and whole grains is recommended to increase the body's antioxidant levels.

What is the chemical nature of benzo[a]pyrene?

Chang Chang-chuan emphasized that there is currently no direct human evidence showing that increased water intake effectively reduces BaP toxicity. Based on existing toxicokinetic data, the expected impact of increased hydration on BaP clearance is anticipated to be extremely limited. Therefore, drinking more water cannot be considered an effective detoxification method after BaP exposure.

Chang explained that benzo[a]pyrene, a Group 1 human carcinogen, is highly hydrophobic and lipophilic. It is a non-polar hydrocarbon composed of five benzene rings. This chemical structure cannot form hydrogen bonds with water molecules, making it water-repellent and highly soluble in organic solvents, oils, and fats. Experiments show that BaP's solubility in octanol (oil) is over 1.3 million times higher than in water. When BaP contacts cells, it can directly 'dissolve into' the hydrophobic (lipophilic) core of the cell membrane without requiring any transporter proteins (carriers). Once inside the membrane, BaP easily crosses this barrier via passive diffusion and enters the cytoplasm, where it can reach the nucleus and interact with DNA.

Does soybean oil increase BaP absorption?

Chang noted that according to the 2017 U.S. EPA 'BaP Toxicological Assessment,' orally ingested BaP is absorbed through the gastrointestinal tract, and high-fat diets or oil-based foods (e.g., corn oil, soybean oil, or triolein) typically increase BaP absorption in the intestines. After intestinal absorption, BaP enters the portal circulation and is transported to the liver, from where it can distribute to multiple organs and tissues throughout the body. BaP metabolism is key to determining its toxicity.

Chang explained that BaP undergoes 'Phase I activation metabolism' by enzymes in human organs, producing BPDE (benzo[a]pyrene-7,8-diol-9,10-epoxide), the most significant carcinogenic metabolite of BaP. BPDE can covalently bind to DNA, forming stable DNA adducts that cause mutations and initiate the carcinogenic process. In the liver, BPDE can undergo further 'Phase II detoxification metabolism' by enzymes, producing water-soluble metabolites that reduce its ability to bind to DNA and enhance excretion via bile and urine. BaP toxicity depends not only on its total concentration in the body but also on the balance between Phase I activation and Phase II detoxification metabolic reactions.

Why is drinking water ineffective for eliminating BaP?

Chang pointed out that the 'BaP Toxicological Assessment' does not state that increased water intake reduces BaP toxicity in humans, nor does it recommend increased hydration as a method to reduce BaP body burden or toxicity. However, the toxicokinetic data described in the document can explain why even if increased water intake has any effect, it would be extremely limited. BaP is not a substance that dissolves in water and is excreted in urine. It must first undergo metabolic activation and conjugation reactions before excretion, and its primary excretion routes are bile and feces, not urine. Therefore, increasing urine output through drinking more water has limited detoxification effects for orally ingested BaP.

How to reduce the body's burden of BaP?

Chang stated that while no major public health or medical institutions provide 'remedial solutions' or antidotes to directly reverse or reduce the carcinogenic toxicity after BaP ingestion, international recommendations for reducing BaP burden in the body generally include:

- Cease consuming BaP-contaminated foods and minimize BaP intake from other food sources, as well as from the two exposure pathways of respiration and skin contact. - Promote a diet centered on fruits, vegetables, legumes, and whole grains to increase the body's antioxidant levels.