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Reference topic 14: The Liver and the Chemical Century

Liver detox: what the liver actually does with modern chemicals

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.72 sources9 graded recommendationsTopic hub: Food

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In the late 1980s the pharmacologist David Bailey and his team in London, Ontario, set out to learn whether alcohol strengthens the effects of felodipine, a blood-pressure drug. According to London Health Sciences Centre, where Bailey worked, he hid the taste of the alcohol in grapefruit juice.1

The juice was meant to be neutral, yet the volunteers' blood held far more felodipine than expected.2 A direct test followed. Six men took felodipine with water, grapefruit juice or orange juice. With grapefruit, nearly three times as much of the drug reached the blood, on average, and the lower blood-pressure reading fell further. "Orange juice had no such effects."3

Mismatch card

The system

The liver, first stop for most of what the gut absorbs: chemical defense and fuel storage.

What it expects

Daily plant defense chemicals, occasional natural toxins such as aflatoxin, and food energy that took work to get.

What it gets

Surplus calories from sugary drinks and alcohol, and more than 350,000 registered chemicals and mixtures, a few of them, such as the long-lived PFAS, beyond its power to break down.

What happens in the gap

About 30% of adults worldwide have fatty livers, and more of them die of heart disease than of liver disease; the main PFAS linger for years in nearly every American's blood.

The handrail

Brisk movement about 150 minutes a week, weight loss where needed, and little or no alcohol (●●●); few sugary drinks (●●○)

Strength of evidence

●●○ Trials show liver fat falls with weight loss, exercise and less sugar; the harms of PFAS at typical exposures, and of microplastics, remain uncertain.

What this topic covers

  • ·The First Pass
  • ·The Goose and the Unnamed Disease
  • ·A Can and Two Apples
  • ·Molecules With No Exit

The practical version is in the book: Chapter 5, Eat.

The handrail

For the liver specifically (Topic 40 holds the full program):

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Cut sugary drinks first

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    In an eight-week trial in 40 teenage boys with fatty liver, the whole household ate meals that held free sugars (added sugars and juice) under 3% of calories. Liver fat fell from 25% to 17%, against 21% to 20% on usual diets.63 In a US study of adults, drinking at least one sugary drink a day was linked to 61% higher odds of fatty liver than drinking none. Diet soda showed no link.64

  2. Keep alcohol low

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Cirrhosis risk climbs steeply with heavy daily drinking, and in women it rises even at one drink a day.65 With significant liver scarring, graded F2 (fibrosis stage 2) or worse, US liver guidelines advise none at all.66 If cutting down is hard, a clinician can help.

  3. Move about 150 minutes a week at brisk-walking effort

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    the dose that lowered liver fat in trials.35

  4. Lose weight if you carry extra

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    A 3-5% loss improves liver fat, but inflammation and scarring generally need more; aim for 10%.6634 Very-low-calorie diets need medical supervision if you take diabetes medication, and they are not for pregnancy or for anyone with a history of eating disorders. Drugs for MASH are a decision for you and your clinician.

  5. Ask about a liver check

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    if you have type 2 diabetes, prediabetes or two or more metabolic risk factors: a FIB-4 (fibrosis-4) score from routine blood tests every one to two years.66 Keep taking a prescribed cholesterol-lowering statin; guidelines call statins safe and recommended in fatty liver disease.66

  6. Skip the detox aisle

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Cabbage-family vegetables measurably sped up a liver enzyme in a 36-person feeding trial;67 eat them as food, not as a cleanse. Supplements can injure the organ some claim to support: herbal and dietary products rose from 7% to 20% of drug-induced liver injury cases in a US network between 2004 and 2013.68 Do not remove intact amalgam fillings to "detox": the US Food and Drug Administration (FDA) does not recommend it, because removal briefly raises mercury exposure. It does advise pregnant or nursing women, young children and some other groups to avoid new amalgam fillings where possible.69

  7. Respect medicine labels

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Acetaminophen (paracetamol) caused 42% of 662 cases of acute liver failure at 22 US hospitals. In 38% of the unintentional overdoses, people had taken two or more acetaminophen products at once.70 Never exceed the stated dose or double up. If a label warns against grapefruit, one fruit is enough to matter.4

  8. Check your water where it matters

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Look up your utility's PFAS results or test a private well. Where PFAS are present, under-sink reverse-osmosis and two-stage filters removed nearly all of them in North Carolina homes. Other carbon filters varied, and some whole-house systems made things worse.71 People with high past exposure, such as firefighters, can ask a clinician about PFAS blood testing.47

  9. Don't microwave food in plastic

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    Heating released the most particles in lab tests.72

The skeptic's corner

The case against this topic, from the research itself.

The dose makes the poison, mostly. In 1538 the physician Paracelsus wrote that "Solely the dose determines that a thing is not a poison." In a modern reappraisal, Grandjean adds that timing and genetic susceptibility matter too, and that missing data are no evidence of safety. He calls PFAS "a clear and unfortunate example."51 For diethylhexyl phthalate (DEHP), a plastic softener, the worry is exposure in the womb. A systematic review rated the evidence "moderate" in humans, and strong in animals, that such exposure shortens baby boys' anogenital distance, the span from anus to genitals (Topic 32).52

PFAS at everyday levels. The liver signal is a raised enzyme, not proven disease. Across two dozen human studies, higher levels of three PFAS went with higher alanine aminotransferase (ALT), an enzyme that leaks from stressed liver cells. In rodents, PFAS consistently raised ALT and fattened the liver.53 Former members of the panel that studied a heavily exposed mid-Ohio Valley community found "an association with liver enzymes, but not with liver disease." They suggested that the link to lower birth weight might run in reverse or reflect some third factor.54 IARC classed PFOA as carcinogenic to humans, but mainly on evidence from animals and from how it acts biologically. It judged the human cancer evidence "limited."42

Microplastics may be partly mismeasured. Both headline studies measured plastic mainly by heating samples until they broke apart, then identifying the fragments. Germany's Federal Institute for Risk Assessment noted that the signals used for polyethylene can overlap with those from ordinary fats. It called the brain amounts "implausibly high."55 A critique in the same journal questioned the brain study's contamination controls, and its authors replied.5657 A study in human blood judged the method, for now, unsuitable for measuring polyethylene and polyvinyl chloride in the body.58 And a small German study that counted particles one by one found none, at the sizes it could detect, in five livers from people without liver disease. Cirrhotic livers held six kinds of plastic.59

Detox. As of a 2015 review, no randomized trials had tested commercial detox diets.60 Young scientists asked the makers of detox products what the word meant. Their verdict: "No two companies seem to use the same definition of 'detox.'"61 Sweat is a trivial exit for long-lived industrial pollutants such as polychlorinated biphenyls (PCBs). By one calculation, two liters a day carry out less than one part in four thousand of a day's dietary intake.62 Your liver and kidneys are the detox system.

Terms this topic defines

Related topics

Sources cited above

  1. 1.London Health Sciences Centre (n.d.). Citrus surprise: A juicy discovery at LHSC changed drug safety around the world. https://www.lhsc.on.ca/150/moment/citrus-surprise-a-juicy-discovery-at-lhsc-changed-drug-safety-around-the-world/
  2. 2.Bailey, D.G., Spence, J.D., Edgar, B., Bayliff, C.D., et al. (1989). "Ethanol enhances the hemodynamic effects of felodipine." Clinical and Investigative Medicine, 12(6), 357-362. https://pubmed.ncbi.nlm.nih.gov/2612087/ (ten people with untreated borderline hypertension; the authors wrote: "felodipine plasma concentrations greatly exceeded the expected concentrations, possibly due to a pharmacokinetic interaction with the grapefruit juice vehicle")
  3. 3.Bailey, D.G., Spence, J.D., Munoz, C., and Arnold, J.M. (1991). "Interaction of citrus juices with felodipine and nifedipine." The Lancet, 337(8736), 268-269. https://doi.org/10.1016/0140-6736(91)90872-M (with grapefruit juice the amount of drug reaching the blood averaged 284% of that with water, and 469% in one man; diastolic blood pressure fell further, and side effects from widened blood vessels came more often)
  4. 4.Bailey, D.G., Dresser, G., and Arnold, J.M. (2013). "Grapefruit-medication interactions: forbidden fruit or avoidable consequences?" CMAJ, 185(4), 309-316 (published online November 2012). https://doi.org/10.1503/cmaj.120951 (furanocoumarins are converted by CYP3A4 into reactive intermediates that "bond covalently to the active site of the enzyme, causing irreversible inactivation"; by 2012 more than 85 drugs were known or predicted to interact with grapefruit, 43 of them with potentially serious effects)
  5. 51.Grandjean, P. (2016). "Paracelsus revisited: the dose concept in a complex world." Basic and Clinical Pharmacology and Toxicology, 119(2), 126-132. https://doi.org/10.1111/bcpt.12622
  6. 52.Dorman, D.C., Chiu, W., Hales, B.F., Hauser, R., et al. (2018). "Systematic reviews and meta-analyses of human and animal evidence of prenatal diethylhexyl phthalate exposure and changes in male anogenital distance." Journal of Toxicology and Environmental Health Part B, 21(4), 207-226. https://doi.org/10.1080/10937404.2018.1505354
  7. 53.Costello, E., Rock, S., Stratakis, N., Eckel, S.P., et al. (2022). "Exposure to per- and polyfluoroalkyl substances and markers of liver injury: a systematic review and meta-analysis." Environmental Health Perspectives, 130(4), 046001. https://doi.org/10.1289/EHP10092 (24 human studies; the chemicals were PFOA, PFOS and PFNA)
  8. 54.Steenland, K., Fletcher, T., Stein, C.R., Bartell, S.M., et al. (2020). "Review: Evolution of evidence on PFOA and health following the assessments of the C8 Science Panel." Environment International, 145, 106125. https://doi.org/10.1016/j.envint.2020.106125 (the review named reverse causation or confounding)
  9. 42.Zahm, S., Bonde, J.P., Chiu, W.A., Hoppin, J., et al. (2024). "Carcinogenicity of perfluorooctanoic acid and perfluorooctanesulfonic acid." Lancet Oncology, 25(1), 16-17. https://doi.org/10.1016/S1470-2045(23)00622-8 (the experts, convened in 2023, wrote: "There is no evidence that PFOA or PFOS are biotransformed")
  10. 55.German Federal Institute for Risk Assessment (BfR) (2025). Microplastics in the brain. Communication No. 056/2025, 12 March 2025. https://www.bfr.bund.de/en/notification/microplastics-in-the-brain/ (the overlap is with "the alkyl chains of fatty acid residues")
  11. 56.Monikh, F.A., Materić, D., Valsami-Jones, E., Grossart, H.P., et al. (2025). "Challenges in studying microplastics in human brain." Nature Medicine, 31(12), 4034-4035. https://doi.org/10.1038/s41591-025-04045-3. Summarized in Yan, B., and Jiang, G. (2026). "Reassessing toxicity claims of micro- and nanoplastics in human health research." Environment and Health, 4(4), 560-562. https://doi.org/10.1021/envhealth.6c00079 (the critique questioned contamination controls and validation)
  12. 57.Campen, M., West, A., Garcia, M., Gullapalli, R., et al. (2025). "Reply to: Challenges in studying microplastics in human brain." Nature Medicine, 31(12), 4036-4037. https://doi.org/10.1038/s41591-025-04046-2
  13. 58.Rauert, C., Charlton, N., Bagley, A., Dunlop, S.A., et al. (2025). "Assessing the efficacy of pyrolysis-gas chromatography-mass spectrometry for nanoplastic and microplastic analysis in human blood." Environmental Science and Technology, 59(4), 1984-1994. https://doi.org/10.1021/acs.est.4c12599 (2025: "currently not a suitable analysis method for PE and PVC in biological matrices")
  14. 59.Horvatits, T., Tamminga, M., Liu, B., Sebode, M., et al. (2022). "Microplastics detected in cirrhotic liver tissue." EBioMedicine, 82, 104147. https://doi.org/10.1016/j.ebiom.2022.104147. The method detected particles of 4-30 micrometers.
  15. 60.Klein, A.V., and Kiat, H. (2015). "Detox diets for toxin elimination and weight management: a critical review of the evidence." Journal of Human Nutrition and Dietetics, 28(6), 675-686. https://doi.org/10.1111/jhn.12286
  16. 61.Sense About Science (2009). Debunking detox. https://senseaboutscience.org/activities/debunking-detox/ (15 detox products)
  17. 62.Imbeault, P., Ravanelli, N., and Chevrier, J. (2018). "Can POPs be substantially popped out through sweat?" Environment International, 111, 131-132. https://doi.org/10.1016/j.envint.2017.11.023. An estimate from the lipid content of sweat, assuming 2 L of sweat a day (1 L of insensible perspiration plus 1 L from physical activity). (less than 0.024% of a day's dietary intake of PCBs)
  18. 63.Schwimmer, J.B., Ugalde-Nicalo, P., Welsh, J.A., Angeles, J.E., et al. (2019). "Effect of a low free sugar diet vs usual diet on nonalcoholic fatty liver disease in adolescent boys: a randomized clinical trial." JAMA, 321(3), 256-265. https://doi.org/10.1001/jama.2018.20579
  19. 64.Ma, J., Fox, C.S., Jacques, P.F., Speliotes, E.K., et al. (2015). "Sugar-sweetened beverage, diet soda, and fatty liver disease in the Framingham Heart Study cohorts." Journal of Hepatology, 63(2), 462-469. https://doi.org/10.1016/j.jhep.2015.03.032
  20. 65.Roerecke, M., Vafaei, A., Hasan, O.S.M., Chrystoja, B.R., et al. (2019). "Alcohol consumption and risk of liver cirrhosis: a systematic review and meta-analysis." American Journal of Gastroenterology, 114(10), 1574-1586. https://doi.org/10.14309/ajg.0000000000000340
  21. 66.Rinella, M.E., Neuschwander-Tetri, B.A., Siddiqui, M.S., Abdelmalek, M.F., et al. (2023). "AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease." Hepatology, 77(5), 1797-1835. https://doi.org/10.1097/HEP.0000000000000323
  22. 35.Stine, J.G., DiJoseph, K., Pattison, Z., Harrington, A., et al. (2023). "Exercise training is associated with treatment response in liver fat content by magnetic resonance imaging independent of clinically significant body weight loss in patients with nonalcoholic fatty liver disease: a systematic review and meta-analysis." American Journal of Gastroenterology, 118(7), 1204-1213. https://doi.org/10.14309/ajg.0000000000002098 (14 randomized trials; smaller doses of exercise did not)
  23. 34.Vilar-Gomez, E., Martinez-Perez, Y., Calzadilla-Bertot, L., Torres-Gonzalez, A., et al. (2015). "Weight loss through lifestyle modification significantly reduces features of nonalcoholic steatohepatitis." Gastroenterology, 149(2), 367-378.e5. https://doi.org/10.1053/j.gastro.2015.04.005 (293 patients; 90% of those who lost at least 10% of their weight saw steatohepatitis resolve; only 30% lost even 5%)
  24. 67.Lampe, J.W., King, I.B., Li, S., Grate, M.T., et al. (2000). "Brassica vegetables increase and apiaceous vegetables decrease cytochrome P450 1A2 activity in humans: changes in caffeine metabolite ratios in response to controlled vegetable diets." Carcinogenesis, 21(6), 1157-1162. https://doi.org/10.1093/carcin/21.6.1157
  25. 68.Navarro, V.J., Barnhart, H., Bonkovsky, H.L., Davern, T., et al. (2014). "Liver injury from herbals and dietary supplements in the U.S. Drug-Induced Liver Injury Network." Hepatology, 60(4), 1399-1408. https://doi.org/10.1002/hep.27317
  26. 69.US Food and Drug Administration (2020). FDA issues recommendations for certain high-risk groups regarding mercury-containing dental amalgam (press announcement, 24 September 2020). https://www.fda.gov/news-events/press-announcements/fda-issues-recommendations-certain-high-risk-groups-regarding-mercury-containing-dental-amalgam
  27. 70.Larson, A.M., Polson, J., Fontana, R.J., Davern, T.J., et al. (2005). "Acetaminophen-induced acute liver failure: results of a United States multicenter, prospective study." Hepatology, 42(6), 1364-1372. https://doi.org/10.1002/hep.20948
  28. 71.Herkert, N.J., Merrill, J., Peters, C., Bollinger, D., et al. (2020). "Assessing the effectiveness of point-of-use residential drinking water filters for perfluoroalkyl substances (PFASs)." Environmental Science and Technology Letters, 7(3), 178-184. https://doi.org/10.1021/acs.estlett.0c00004
  29. 47.National Academies of Sciences, Engineering, and Medicine (2022). Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. National Academies Press. https://doi.org/10.17226/26156
  30. 72.Hussain, K.A., Romanova, S., Okur, I., Zhang, D., et al. (2023). "Assessing the release of microplastics and nanoplastics from plastic containers and reusable food pouches: implications for human health." Environmental Science and Technology, 57(26), 9782-9792. https://doi.org/10.1021/acs.est.3c01942

This topic carries 72 notes in the research manuscript; the 30 above are those behind the material on this page. Full source register.