Who Should Avoid Turmeric Supplements

Table of Contents

1. Spice Is Not Supplement
2. Gallstones and Bile-Duct Obstruction
3. Calcium-Oxalate Kidney Stones
4. Iron Deficiency and Low Iron Stores
5. Surgery, Dental Work and Bleeding Risk
6. Transplant Recipients and Narrow-Therapeutic-Index Drugs
7. Existing Liver Disease
8. Pregnancy and Breastfeeding
9. Children, Reflux and Sensitive Stomachs
10. What the Trials Actually Dosed
11. Why the Literature Itself Needs Care
12. The Recap
13. Key Research Papers
14. Connections
15. Featured Videos

Spice Is Not Supplement

Before the list, the distinction that makes sense of all of it.

Turmeric powder is mostly starch and fibre, with curcuminoids at a few percent, and those curcuminoids are absorbed so poorly that even a heavily spiced diet produces low blood concentrations. That is the exposure under which turmeric earned its long, quiet safety record across more than a thousand years of daily use.

A standardised extract concentrates curcuminoids to around 95% — a twenty- to thirtyfold step before anything else happens — and modern formulations then add a delivery system engineered specifically to defeat poor absorption. Black-pepper extract blocks the enzymes that dispose of curcumin; phospholipid complexes, submicron colloids, solid lipid particles and micelles each attack a different barrier. The result is intentional: several times more curcumin in the blood at the same label dose. Our bioavailability and forms page explains the engineering.

So "avoid turmeric" is almost always the wrong instruction. The right instruction is nearly always "skip the concentrated supplement" — which for most of the groups below costs nothing at all, because the spice was never the thing at issue.

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Gallstones and Bile-Duct Obstruction

Evidence: human ultrasound studies. This is one of the better-supported cautions here.

Rasyid and Lelo published a placebo-controlled ultrasound study in Alimentary Pharmacology & Therapeutics in 1999 examining the effect of curcumin on human gallbladder function. Curcumin caused the gallbladder to contract. Rasyid, Rahman, Jaalam and colleagues followed this in the Asia Pacific Journal of Clinical Nutrition in 2002 with a study of different curcumin doses on the human gallbladder.

The mechanism is straightforward and, in most circumstances, entirely benign. The gallbladder stores bile and squeezes it into the small intestine when fat arrives. Turmeric is a cholagogue — a substance that prompts that squeeze — which is one of the oldest documented traditional uses of the plant and part of why it appears in digestive formulas across several medical traditions. Healthy gallbladder, working duct: the squeeze is normal physiology and helps with fat digestion.

The problem is a gallbladder with a stone in the wrong place, or a duct that is blocked or narrowed. Now you have a muscular organ contracting hard against an obstruction, which is the anatomy of biliary colic — the severe, gripping right-upper-abdomen pain that sends people to emergency departments. Deliberately stimulating that contraction is the wrong thing to ask of that anatomy.

Who this applies to: anyone with known gallstones, a history of biliary colic, a bile-duct obstruction or stricture, or a known biliary abnormality. If you have had your gallbladder removed, it does not apply — there is no gallbladder left to contract, and bile simply drains continuously.

This is one of the two entries where large culinary intakes are worth a thought, since the effect is a response to turmeric itself rather than to a formulation. Ordinary seasoning is not the concern; a daily golden-milk habit built on heaped spoonfuls, in somebody with symptomatic stones, is worth noticing. If eating turmeric-heavy food reliably brings on right-sided pain, that observation is worth reporting to a doctor — it is information about your gallbladder, not just about your dinner.

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Calcium-Oxalate Kidney Stones

Evidence: a human crossover study with a clean comparator.

Tang, Larson-Meyer and Liebman published a study in the American Journal of Clinical Nutrition in 2008 on the effect of cinnamon and turmeric on urinary oxalate excretion, plasma lipids and plasma glucose in healthy subjects. Turmeric raised urinary oxalate excretion. Cinnamon did not.

The internal comparison is what makes this study worth citing. Two spices, the same design, the same participants, and only one produced the effect — which is far more informative than a single-arm observation, because it rules out a generic effect of "eating a spice" and points at turmeric's own oxalate content and how it is handled.

Why oxalate matters: the most common kidney stones are calcium oxalate. They form when calcium and oxalate concentrations in the urine are high enough for crystals to nucleate and grow. Dietary oxalate is one of several contributors — fluid intake, urine calcium, citrate, sodium and the balance of calcium in the same meal all matter too — but for people who form these stones repeatedly, oxalate intake is one of the levers doctors actually pull, which is why low-oxalate diets exist.

Who this applies to: people who have formed calcium-oxalate stones, and particularly anyone following a low-oxalate diet on medical advice. If you are on a low-oxalate diet and taking a high-dose turmeric supplement, you are working against yourself. Discuss it with whoever manages your stone prevention — they will know your urine chemistry, and the answer may differ depending on whether your stones are oxalate-driven at all.

This is the second entry where culinary amounts deserve a mention, because it is the spice's own oxalate that was measured. The practical steps are ordinary: drink more water, take turmeric with a calcium-containing food (calcium binds oxalate in the gut, so less is absorbed), and keep the total in proportion. For people who have never had a kidney stone, this is not a reason to change anything.

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Iron Deficiency and Low Iron Stores

Evidence: a well-characterised mechanism in animals and cells, plus one human case report.

Jiao, Wilkinson, Di and colleagues showed in Blood in 2009 that curcumin acts as a biologically active iron chelator — binding iron and producing the downstream signs of iron depletion in animals, not merely sticking to iron in a test tube. Smith and Ashar then reported in Cureus in 2019 a case of iron-deficiency anaemia attributed to high-dose turmeric, which resolved when the turmeric was stopped.

One case report is a weak foundation on its own. Paired with a demonstrated mechanism and a resolution on withdrawal, it is enough to be worth knowing about — particularly since the people most at risk are easy to identify in advance.

Who this applies to:

• Anyone diagnosed with iron-deficiency anaemia or low ferritin.
• People with heavy menstrual bleeding.
• Vegetarians and vegans, whose dietary iron is less readily absorbed to begin with.
• People with coeliac disease, inflammatory bowel disease or other malabsorption, and anyone who has had bariatric surgery.
• Blood donors who give regularly.
• Anyone taking an iron supplement — separate it from turmeric by several hours, since the binding happens in the gut and timing genuinely helps.

If you are in one of these groups and want to take turmeric anyway, the sensible arrangement is to have ferritin checked before starting and again after a few months. That converts an invisible risk into a measured one, which is the general theme of this leg of the site.

For people with normal iron stores, mild chelation is not obviously a problem, and some of curcumin's proposed effects have been attributed to this very property. The concern is specific to those whose iron is already low.

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Surgery, Dental Work and Bleeding Risk

Evidence: a theoretical mechanism. The one human interaction study found nothing. Recommend the pause anyway, and say why.

Curcumin has been shown in laboratory work to interfere with platelet aggregation. That is the basis for turmeric appearing on every "herbs that thin the blood" list, and it is a reasonable mechanistic concern.

It is also, so far, unconfirmed in people. Hu, Belcaro, Dugall and colleagues studied a bioavailable curcumin formulation alongside antiplatelet agents, anticoagulants and thyroid replacement therapy in 2018 and reported no significant interaction. That study has limits — observational, one formulation, and a null result can reflect limited power — but it is the human evidence available, and reporting it accurately matters more than preserving a tidy warning. Our drug-interactions page covers the anticoagulant question in full.

So why still recommend stopping before surgery? Because of the shape of the decision, not the strength of the evidence. Pausing a supplement for one to two weeks costs you essentially nothing — no supplement on earth delivers a benefit that collapses over a fortnight. Bleeding during or after an operation costs a great deal. When one side of a decision is free and the other is expensive, you do not need strong evidence to choose; you need only the possibility of an effect. That is prudence, and it should be labelled as prudence rather than dressed up as a proven danger.

Practical version: stop turmeric supplements one to two weeks before planned surgery, dental extractions, colonoscopy with likely biopsy, injections into joints or the spine, and cosmetic procedures. Tell the anaesthetist and the surgeon what you have been taking — supplements are frequently omitted from medication lists, and surgical teams genuinely want to know. Food-level turmeric does not need to stop. Resume afterwards when your surgeon is happy with the wound.

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Transplant Recipients and Narrow-Therapeutic-Index Drugs

Evidence: three human case reports. The firmest recommendation on this page, and not because the evidence is strongest.

A narrow-therapeutic-index drug is one where the gap between too little and too much is small. Tacrolimus and cyclosporine — the calcineurin inhibitors that stop a transplanted organ being rejected — are the classic examples, which is why recipients have blood levels measured repeatedly, sometimes for the rest of their lives. Too low risks the graft; too high damages the kidneys.

Three case reports involve turmeric. Boissiere and colleagues described spice–drug interactions in a renal transplant patient on tacrolimus using turmeric, curry and ginger. Nayeri and colleagues described acute calcineurin-inhibitor nephrotoxicity following turmeric intake. A 2010 Swedish report, published without a listed author, described a possible turmeric–tacrolimus interaction. The plausible mechanism is interference with the enzymes and transporters that clear these drugs — the same route by which grapefruit juice raises tacrolimus, which transplant teams already warn about.

Three case reports would normally support a mild caution at most. Here the recommendation is firm, for the reason set out on the interactions page: the cost of skipping a turmeric supplement is zero, and the cost of being wrong is graft rejection or kidney injury. That asymmetry decides it.

Who this applies to: anyone with a transplanted organ; anyone on tacrolimus, cyclosporine or similar immunosuppression for any reason; and, by the same logic, people on other narrow-index medicines — lithium, digoxin, some antiepileptics, and drugs whose levels are routinely monitored. Curcumin has not been studied with most of those, which is exactly the point: an unstudied variable added to a finely titrated regimen is a bad trade.

The Boissiere report is also a reminder that in this one population, culinary intake is worth mentioning too. If your cooking changes substantially — a new diet, a much more heavily spiced household — tell the transplant team. In most contexts "it's only food" is a fair argument. In transplant medicine it is weaker than usual.

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Existing Liver Disease

Evidence: an inference from the case literature rather than a study of this group.

There is an irony here worth naming. Turmeric is widely promoted for liver health, and there is real research behind that interest — our page on turmeric and liver health covers it. Yet the best-documented harm from concentrated turmeric supplements is liver injury.

Both can be true, and the resolution is the same as everywhere else on this leg: the trials studying benefit and the case reports describing harm are describing different exposures, different products and different people. But it does mean that anyone with existing liver disease should think carefully, for three reasons:

1. Less reserve. A liver already compromised by fatty liver disease, hepatitis, cirrhosis or an autoimmune condition has less capacity to absorb an additional insult.
2. Harder to detect. If your liver enzymes are already abnormal, the rise that would signal drug-induced injury in someone else is much harder to spot against your background.
3. Harder to attribute. If something goes wrong, working out whether it was the supplement or the underlying disease is genuinely difficult, and that uncertainty complicates your care.

The same applies if you drink heavily, take other medicines known to affect the liver, or have had drug-induced liver injury from anything before — a previous idiosyncratic reaction is a marker of susceptibility.

Halegoua-DeMarzio and Navarro's review in Liver International on the challenges of identifying and preventing herbal-induced liver injury is the honest overview of this field. If you have liver disease and want to take turmeric anyway, do it as a supervised experiment: tell your hepatologist, agree a product and a dose, and monitor enzymes. That is a reasonable request, and most specialists would rather have the conversation than find out later. The full picture is on our liver-injury page.

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Pregnancy and Breastfeeding

Evidence: an absence of study, which is not the same as evidence of harm. This section deliberately cites no paper, because none in our verified set addresses pregnancy.

Here is the honest position, in two parts.

Turmeric as a food is regarded as fine. It is eaten daily throughout pregnancy across enormous populations and has been for many centuries, and it is a normal part of the diet in cultures where it is a kitchen staple. Nobody sensible suggests a pregnant woman should avoid curry.

Turmeric supplements at concentrated doses are not well studied in pregnancy. That is a statement about the state of the literature, not about danger. Pregnant women are, for understandable reasons, excluded from most trials of most substances, which means the evidence base for supplements in pregnancy is thin almost across the board. A reader deserves to be told that clearly rather than handed either a false reassurance or a false alarm.

What follows from a genuine unknown is a matter of judgement, and the judgement most people reach is the conservative one: during pregnancy and breastfeeding, get turmeric from food, where the safety record is long and the dose is modest, and leave the concentrated extract until afterwards. Not because it has been shown to cause harm — it has not — but because the reason to take a supplement during pregnancy has to be strong enough to outweigh an unmeasured risk, and for most people it is not.

If you are pregnant and have been taking a turmeric supplement, this is not cause for alarm. Mention it at your next appointment, as you would any supplement. If you are taking it for a specific medical reason, that is a conversation with the doctor managing the condition, who can weigh your particular situation.

To read the primary literature yourself: PubMed: Curcumin and pregnancy safety and PubMed: Turmeric during lactation and breastfeeding.

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Children, Reflux and Sensitive Stomachs

Two smaller groups, handled briefly and honestly.

Children. Turmeric in food is normal for children in every cuisine that uses it. Concentrated supplements for children are a different question, and the evidence base is essentially the same as for pregnancy: thin, because children are rarely enrolled in supplement trials. Dosing has not been established, children are not small adults metabolically, and the case for giving a healthy child a concentrated botanical extract is usually weak. If a child has a condition for which someone has suggested curcumin, that is a paediatrician's conversation. Relevant reading: PubMed: Curcumin supplementation in children.

Reflux and sensitive stomachs. Turmeric stimulates bile flow and gastric secretion, and a minority of people find that concentrated doses produce heartburn, reflux, nausea or loose stools. This is a tolerability issue rather than a safety one — unpleasant, not dangerous — and it is dose-related in a way that idiosyncratic liver injury is not. Taking it with food usually helps, as does a lower dose. If it consistently makes your stomach worse, that is a reasonable signal to stop; a supplement causing symptoms every day is not earning its place. Our page on turmeric and digestive health covers the gut effects in both directions, since the same bile-stimulating property that bothers some people is the basis of its traditional digestive use.

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What the Trials Actually Dosed

It helps to know what "high dose" means in the hands of people doing this deliberately, under supervision. Three phase I studies give the scale.

Cheng, Hsu, Lin and colleagues (2001), in Anticancer Research, ran a phase I trial of curcumin in patients with high-risk or pre-malignant lesions, escalating oral doses to find the limits of tolerability.

Sharma, McLelland, Hill and colleagues (2001), in Clinical Cancer Research, gave oral Curcuma extract to patients with colorectal cancer and measured both what happened pharmacologically and what reached the tissue — a study designed as much to understand the absorption problem as to test an effect.

Kanai, Otsuka, Otsuka and colleagues (2013), in Cancer Chemotherapy and Pharmacology, did the equivalent work with a highly bioavailable colloidal formulation (Theracurmin) in cancer patients — the modern version of the question, where the delivery problem has been partly solved.

Three things follow for a general reader. First, gram-level daily doses were tolerated by most participants in short, monitored courses, which is genuinely reassuring about acute toxicity. Second, the doses in the unenhanced studies had to be enormous because the body discards most of it — the size of the number reflects the absorption problem, not a therapeutic requirement. Third, and most important: these were supervised trials in patients with serious illness, with monitoring and follow-up. They are not a licence for anyone to take grams of curcumin daily, indefinitely, unsupervised, in a formulation designed to deliver several times more into the blood than the trials achieved. That combination — high dose, enhanced absorption, long duration, nobody watching — is the profile that shows up in the case literature.

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Why the Literature Itself Needs Care

A page telling you who should avoid turmeric supplements owes you one more thing: a reason to be sceptical of the enthusiasm on the other side.

Nelson, Dahlin, Bisson and colleagues (2017), in the Journal of Medicinal Chemistry: "The Essential Medicinal Chemistry of Curcumin." This is the most cited critique in the field. Its argument is that curcumin is what chemists call a PAINS compound — pan-assay interference — and an invalid metabolic panacea. Molecules of this type have chemical properties that make them produce apparent hits in a very wide range of laboratory assays through mechanisms unrelated to genuine biological activity: interfering with fluorescence readouts, reacting non-specifically with proteins, aggregating and dragging targets down with them. The paper also notes that despite decades of intense study, no curcumin formulation had succeeded in a definitive clinical trial in the way the laboratory literature would predict.

This is not a fringe position, and it does not say curcumin does nothing. It says the enormous in-vitro literature — the source of most "curcumin targets 200 molecular pathways" claims — is much less reliable than its volume suggests, and that claims should rest on human trials.

Burgos-Morón, Calderón-Montaño, Salvador and colleagues (2010), in the International Journal of Cancer: "The dark side of curcumin." A review collecting the evidence that curcumin is not uniformly benign — that at some concentrations and in some systems it produces effects nobody would want, which is a normal property of biologically active molecules and an abnormal thing to find discussed in supplement marketing.

Two further papers are worth naming for anyone comparing bioavailability claims, because they concern how the measurements are made. Stohs and colleagues (2019) argued that the enzymatic-hydrolysis method commonly used to determine curcumin in plasma is a flawed indicator of bioavailability, and Luis and colleagues (2020) showed that the hydrolysis step is incomplete, with complex conjugates detectable in plasma. Between them they imply that some published bioavailability multiples rest on an assay that may not measure what it claims — which is worth knowing when a label advertises a number.

The practical reading: be equally sceptical of "curcumin cures everything" and "turmeric destroys your liver." Both claims are usually built out of laboratory findings promoted beyond their weight. The defensible middle is that concentrated curcumin is a real biologically active substance with modest evidence for some uses, an uncommon but genuine capacity for harm, and a product category where what is on the label and what reaches your blood are not the same number.

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The Recap

The single most useful sentence on this page: spice is not supplement.

Turmeric in your cooking is one of the best-established safe foods there is. Eaten daily by hundreds of millions of people for centuries, it delivers a small amount of a poorly absorbed compound, and none of the harms documented in this leg of the site come from it. If you finish this page and stop putting turmeric in your food, you have taken the wrong message from it.

A concentrated curcumin supplement, particularly an absorption-enhanced one, is a different proposition. It is a pharmacological dose of a biologically active molecule, and it should be treated the way you would treat any other: with a reason for taking it, a defined dose, an end point, an eye on interactions, and attention to how you feel. That is not a warning about turmeric. It is what taking anything seriously looks like.

For most of the groups on this page, the answer is not "avoid turmeric." It is "keep cooking with it and skip the capsule" — and for many of them the capsule was not going to deliver much anyway.

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Key Research Papers

1. Rasyid A, Lelo A. (1999). The effect of curcumin and placebo on human gall-bladder function: an ultrasound study. Aliment Pharmacol Ther. — PubMed PMID: 10102956
2. Rasyid A, Rahman AR, Jaalam K, et al. (2002). Effect of different curcumin dosages on human gall bladder. Asia Pac J Clin Nutr. — PubMed PMID: 12495265
3. Tang M, Larson-Meyer DE, Liebman M. (2008). Effect of cinnamon and turmeric on urinary oxalate excretion, plasma lipids, and plasma glucose in healthy subjects. Am J Clin Nutr. — PubMed PMID: 18469248
4. Jiao Y, Wilkinson J 4th, Di X, et al. (2009). Curcumin, a cancer chemopreventive and chemotherapeutic agent, is a biologically active iron chelator. Blood. — PubMed PMID: 18815282
5. Smith TJ, Ashar BH. (2019). Iron Deficiency Anemia Due to High-dose Turmeric. Cureus. — PubMed PMID: 30899609
6. Hu S, Belcaro G, Dugall M, et al. (2018). Interaction study between antiplatelet agents, anticoagulants, thyroid replacement therapy and a bioavailable formulation of curcumin (Meriva). Eur Rev Med Pharmacol Sci. — PubMed PMID: 30070343
7. Boissiere C, Francois E, Vabret E, et al. (2023). Spice-drug interactions: a case report on the use of turmeric, curry and ginger in a renal transplant patient on tacrolimus. Eur J Hosp Pharm. — PubMed PMID: 37586787
8. Nayeri A, Wu S, Adams E, et al. (2017). Acute Calcineurin Inhibitor Nephrotoxicity Secondary to Turmeric Intake: A Case Report. Transplant Proc. — PubMed PMID: 28104136
9. (2010). [Interaction between turmeric and tacrolimus possible]. Lakartidningen. — PubMed PMID: 20521597 (no author list is returned for this record)
10. Halegoua-DeMarzio D, Navarro V, Ahmad J, et al. (2023). Liver Injury Associated with Turmeric—A Growing Problem: Ten Cases from the Drug-Induced Liver Injury Network [DILIN]. Am J Med. — PubMed PMID: 36252717
11. Halegoua-DeMarzio D, Navarro V. (2025). Challenges in herbal-induced liver injury identification and prevention. Liver Int. — PubMed PMID: 39136211
12. Akhtar N, Barnes J, Gardiner P, et al. (2026). Rarely reported cases of hepatotoxicity associated with turmeric- and curcuminoid-containing dietary supplements: a comprehensive review by USP. Pharm Biol. — PubMed PMID: 42364655
13. Cheng AL, Hsu CH, Lin JK, et al. (2001). Phase I clinical trial of curcumin, a chemopreventive agent, in patients with high-risk or pre-malignant lesions. Anticancer Res. — PubMed PMID: 11712783
14. Sharma RA, McLelland HR, Hill KA, et al. (2001). Pharmacodynamic and pharmacokinetic study of oral Curcuma extract in patients with colorectal cancer. Clin Cancer Res. — PubMed PMID: 11448902
15. Kanai M, Otsuka Y, Otsuka K, et al. (2013). A phase I study investigating the safety and pharmacokinetics of highly bioavailable curcumin (Theracurmin) in cancer patients. Cancer Chemother Pharmacol. — PubMed PMID: 23543271
16. Nelson KM, Dahlin JL, Bisson J, et al. (2017). The Essential Medicinal Chemistry of Curcumin. J Med Chem. — PubMed PMID: 28074653
17. Burgos-Morón E, Calderón-Montaño JM, Salvador J, et al. (2010). The dark side of curcumin. Int J Cancer. — PubMed PMID: 19830693
18. Stohs SJ, Chen CYO, Preuss HG, et al. (2019). The fallacy of enzymatic hydrolysis for the determination of bioactive curcumin in plasma samples as an indication of bioavailability. BMC Complement Altern Med. — PubMed PMID: 31684927
19. Luis PB, Kunihiro AG, Funk JL, et al. (2020). Incomplete Hydrolysis of Curcumin Conjugates by β-Glucuronidase: Detection of Complex Conjugates in Plasma. Mol Nutr Food Res. — PubMed PMID: 31962379
20. Shoba G, Joy D, Joseph T, et al. (1998). Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Med. — PubMed PMID: 9619120

PubMed Topic Searches

1. PubMed: Curcumin and pregnancy safety
2. PubMed: Turmeric during lactation and breastfeeding
3. PubMed: Curcumin supplementation in children
4. PubMed: Dietary oxalate and calcium-oxalate kidney stones
5. PubMed: Herbal supplements and perioperative bleeding risk
6. PubMed: Curcumin and gallbladder function

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Connections

• Turmeric Safety and Drug Interactions
• Turmeric and Liver Injury
• Turmeric Drug Interactions
• Lead in Turmeric
• Bioavailability and Forms
• Turmeric for Liver Health
• Turmeric and Digestive Health
• Heart and Metabolic Health
• Anti-Inflammatory and Joint Health
• Turmeric Benefits
• Turmeric
• Culinary and Spice Herbs
• Gut Health
• Herbs

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