Hyperlipidemia supporting liver function and metabolism of glucose, lipids, and hormones. Liver disease including cirrhosis, cancer prevention, hepatitis, and viral-induced inflammation and protection from exogenous chemicals and toxins1 (parenteral preparations have become established as a viable treatment to save the liver after acute ingestion of hepatotoxins such as poison mushrooms2,3). Diabetes, metabolic syndrome, hyperglycemia, and insulin resistance.
Mechanism of Action
Nearly all of the research on Silybum has focused on the silymarin complex, a mixture of flavonolignans obtained from the seeds. Silymarin includes the individual flavonolignans silybin A and silybin B (two isomers, together referred to as silibinin4), isosilybin A and isosilybin B (two isomers), silydianin, and silychristin. Silymarin also contains fatty acids5 and a flavanone dihydroquercetin (taxifolin),6 also credited with medicinal effects. Silybin is sometimes mixed with phosphatidylcholine to treat liver disease.7 Whole silymarin mixture has been shown to be a superior hypocholesterolemic medication compared with isolated silybin, one of the major flavonolignans found in silymarin.8
Silibinin is itself a mixture of two diastereoisomers, silybin A and silybin B.4 Silibinin is considered one of the most active hepatoprotective constituents of Silybum seeds, and it is one of the agents believed to protect mitochondrial function and has been shown to increase hepatocellular ATP when studied in isolation.9
Silybum flavonolignans are credited with significant antioxidant and membrane-stabilizing effects on hepatocytes.10 Unlike many statin drugs associated with muscle and liver toxicity, Silybum increases high-density lipoprotein, reduces liver cholesterol deposition, and offers hepatoprotective effects.8 Liver injury results in dyslipoproteinemia, which may lead to the development of atherosclerosis, particularly when associated with hypercholesterolemia.
Silybum improves hepatic regulation of plasma lipoproteins and may directly inhibit cholesterol biosynthesis.11 Silybum significantly improves liver enzymes in nonalcoholic fatty liver disease.12 Parameters indicative of early-stage atherosclerosis may be lowered by Silybum.12 Silymarin has been shown promote superoxide dismutase and glutathione in liver cells in animals fed a high-sucrose diet, which can result in improved lipoprotein and triglyceride levels.13 Oil from Silybum seeds has been shown to attenuate oxidative damage and liver mitochondrial dysfunction in aging mice.5
Silybum has been studied for several decades now and is shown to have broad hepatoprotective and metabolic effects including antioxidant and anti-inflammatory activities, cell permeability regulation and membrane stabilization, stimulation of liver regeneration, and inhibition of deposition in collagen, which may contribute to cirrhosis.14 A 2014 review of Phase III clinical trials report silymarin to be the best medication for nonalcoholic fatty liver disease.15
A randomized controlled trial (RCT) dosed diabetic patients with either 1000 mg/day of berberine or a combo of 1000 mg of berberine and 210 mg of silymarin. Although both treatments improved fasting glucose, total cholesterol, low-density lipoprotein (LDL) cholesterol, triglyceride, and liver enzyme levels, glycosylated hemoglobin (HbA1c) values were reduced to a greater extent by the combination.16 A similar RCT investigated the effects of the combination of berberine and silymarin on cholesterol in patients with statin intolerance. The combination significantly reduced triglycerides, LDL cholesterol, fasting blood glucose, and glycosylated hemoglobin17 without inducing toxicity conditions seen with statins.18 Additional similar studies on this combination have shown positive effects on reducing insulin resistance17 and adipokine elevations19 and improved glycemic control with a glucagon challenge.20
A study on Silybum combined with selenium was investigated in men after radical prostatectomy revealed the incidental finding of reduced LDL and total cholesterol.21
An RCT on diabetic patients investigated the effects of 200 mg of Silybum taken two times per day on glycemic indices compared with placebo. Silybum was associated with a significant decrease in HbA1c, fetal bovine serum, total cholesterol, LDL, and triglycerides serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase levels compared with placebo.22
Safety in Pregnancy and Breastfeeding
Because of its long-standing history as a wild food—the leaves, the roots, and the seeds—Silybum is assumed safe during pregnancy. Silybum is considered safe in lactation and, in fact, is a folkloric galactogogue,23 with modern clinical trials showing efficacy in promoting lactation in preterm mothers with infants in the neonatal intensive care unit.24 Another study compared 429 mg of silymarin per day with placebo in nursing women with hypogalactia and reported clear galactogogue effects calculated to be an 85.94% increase in breast milk production from Silybum without side effects or difficulties in tolerance.25
Silybum is considered to be safe in both short- and long-term applications. Because of its extensive use as a modern natural medicine, Silybum has been the beneficiary of extensive studies by the National Institute of Environmental Health Sciences. The animal investigations found no significant toxicities, no interference with reproductive functions, and no carcinogenic effects26. Animals with long-term Silybum exposure displayed a significantly lower incidence of bile duct hyperplasia, lower mean body weights, significantly decreased incidences of hepatocellular adenoma and hepatocellular carcinoma, and decreased incidences of mammary gland neoplasms in exposed groups of female rats.27 A 2-year toxicity study dosing Silybum to rats and mice found no significant toxicity and a reduction in background tumors.28
No adverse effects or toxicities were noted in any of the human trials cited. A 2007 review of clinical trials reported Silybum extracts to be safe, well tolerated, and toxic or adverse effects to be minimal.29 The main side effects of silymarin seem to be rare gastrointestinal disturbances and allergic skin rashes.30 Oral doses of silymarin up to 2.1 g/day have been shown to be well tolerated and not associated with side effects in human HCV patients.31
Silybum, and particularly isolated silybin, are potent inhibitors of cytochrome P2C932 and cytochrome P3A33 groups of enzymes; however, isolated silybin was not shown to have significant interactions with other drugs and at doses 26 No antagonistic interactions are noted between Silybum and vincristine, and a modest synergistic effect has been demonstrated.34 No drug-related adverse events were reported.31
Silybum is generally considered safe at doses up to 700 mg per day. Because Silybum has been so widely studied, medicinal products and clinical studies are often standardized to approximately 80% silymarin content. Dosages may range from 50 to 200 mg or more of Silybum taken two or three times daily to support liver function, reduce cholesterol, and improve glycemic control.
Nonlinear pharmacokinetics of silybin A and silybin B suggests low bioavailability associated with customary doses of silymarin may be overcome with doses above 700 mg.31 Pharmacokinetic studies in human HCV patients have shown a nonlinear dose–blood level curve where doses of 140, 280, and 560 mg result in similar blood levels that suddenly jump at dose of 700 mg.31
The liver is greatly involved in processing lipids and cholesterol and liver herbs can be an important component of treatments for hyperlipidemia.
Silybum has been used as herbal medicine for the treatment of liver disease and liver cirrhosis and
to prevent liver cancer in Europe and Asia since ancient times. Silybum has also been used to treat gallbladder and biliary disease, jaundice, peritonitis, malarial fevers, bronchitis, insufficient lactation, varicose veins, and reduce insulin resistance. The roots of Silybum have been prepared as a medicinal food, and the spines can be cut from leaves and used a salad greens and pot herbs. Silybum seeds have been roasted brewed into teas and coffee substitutes. Recent research is also showing the Silybum can be useful for renal disease and inflammation and may have efficacy against hormonal cancers including breast, cervical, and prostate.
J Sci Food Agric. 2012;92(7):1441–7. Hepatoprotection of silymarin against thioacetamide-induced chronic liver fibrosis. Chen IS, Chen YC, Chou CH, Chuang RF, Sheen LY, Chiu CH.
2 Przegl Lek. 2012;69(8):541–3. Silibinin and its hepatoprotective action from the perspective of a toxicologist. Kostek H, Szponar J, Tchórz M, Majewska M, Lewandowska-Stanek H.
3 Curr Pharm Biotechnol. 2012;13(10):1964–70. Legalon® SIL: the antidote of choice in patients with acute hepatotoxicity from amatoxin poisoning. Mengs U, Pohl RT, Mitchell T.
4 Chem Biol Interact. 2012;195(2):119–32. Metabolic effects of silibinin in the rat liver. Colturato CP, Constantin RP, Maeda AS Jr, Constantin RP, Yamamoto NS, Bracht A, Ishii-Iwamoto EL, Constantin J.
5 Pharmacogn Mag. 2014;10(Suppl 1):S92–9. Silybum marianum oil attenuates oxidative stress and ameliorates mitochondrial dysfunction in mice treated with D-galactose. Zhu SY, Dong Y, Tu J, Zhou Y, Zhou XH, Xu B.
6 Eur J Pharmacol. 2012;684(1–3):19–26. Dihydroquercetin: More than just an impurity? Weidmann AE.
7 Integr Cancer Ther. 2014;13(1):46–53. A phase I dose-finding study of silybin phosphatidylcholine (milk thistle) in patients with advanced hepatocellular carcinoma. Siegel AB, Narayan R, Rodriguez R, Goyal A, Jacobson JS, Kelly K, Ladas E, Lunghofer PJ, Hansen RJ, Gustafson DL, Flaig TW, Tsai WY, Wu DP.
8 Planta Med. 1998;64(2):138–42. Silymarin inhibits the development of diet-induced hypercholesterolemia in rats. Krecman V, Skottová N, Walterová D, Ulrichová J, Simánek V.
9 J Ethnopharmacol. 2008;115(3):507–14. Antioxidant and mitochondrial protective effects of silibinin in cold preservation-warm reperfusion liver injury. Ligeret H, Brault A, Vallerand D, Haddad Y, Haddad PS.
10 Food Chem Toxicol. 2010;48(3):803–6. Silymarin, the antioxidant component and Silybum marianum extracts prevent liver damage. Shaker E, Mahmoud H, Mnaa S.
11 Physiol Res. 1998;47(1):1–7. Silymarin as a potential hypocholesterolaemic drug. Skottová N, Krecman V.
12 World J Hepatol. 2013;5(3):109–13. Silymarin in non-alcoholic fatty liver disease. Cacciapuoti F, Scognamiglio A, Palumbo R, Forte R, Cacciapuoti F.
13 Pharmacol Res. 2004;50(2):123–30. Phenolics-rich extracts from Silybum marianum and Prunella vulgaris reduce a high-sucrose diet induced oxidative stress in hereditary hypertriglyceridemic rats. Skottová N, Kazdová L, Oliyarnyk O, Vecera R, Sobolová L, Ulrichová J.
14 J Evid Based Complementary Altern Med. 2015;20(4):292–301. Silybum marianum: Beyond hepatoprotection. Bahmani M, Shirzad H, Rafieian S, Rafieian-Kopaei M.
15 Rev Recent Clin Trials. 2014;9(3):195–203. Phytotherapy and NAFLD – from goals and challenges to clinical practice. Milosevic N, Milanovic M, Abenavoli L, Milic N.
16 Clin Pharmacol. 2013;5:167–74. Preliminary study about the possible glycemic clinical advantage in using a fixed combination of Berberis aristata and Silybum marianum standardized extracts versus only Berberis aristata in patients with type 2 diabetes. Di Pierro F, Putignano P, Villanova N, Montesi L, Moscatiello S, Marchesini G.
17 Diabetes Metab Syndr Obes. 2012;5:213–7. Pilot study on the additive effects of berberine and oral type 2 diabetes agents for patients with suboptimal glycemic control. Di Pierro F, Villanova N, Agostini F, Marzocchi R, Soverini V, Marchesini G.
18 Diabetes Metab Syndr Obes. 2015;8:89–96. Clinical role of a fixed combination of standardized Berberis aristata and Silybum marianum extracts in diabetic and hypercholesterolemic patients intolerant to statins. Di Pierro F, Bellone I, Rapacioli G, Putignano P.
19 J Biol Regul Homeost Agents. 2013;27(3):717–28. Effects of Berberis aristata/Silybum marianum association on metabolic parameters and adipocytokines in overweight dyslipidemic patients. Derosa G, Bonaventura A, Bianchi L, Romano D, D’Angelo A, Fogari E, Maffioli P.
20 Expert Opin Biol Ther. 2013;13(11):1495–506. Berberis aristata/Silybum marianum fixed combination on lipid profile and insulin secretion in dyslipidemic patients. Derosa G, Bonaventura A, Bianchi L, Romano D, D’Angelo A, Fogari E, Maffioli P.
21 Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2010;154(3):239–44. The safety and efficacy of a silymarin and selenium combination in men after radical prostatectomy – a six month placebo-controlled double-blind clinical trial. Vidlar A, Vostalova J, Ulrichova J, Student V, Krajicek M, Vrbkova J, Simanek V.
22 Phytother Res. 2006;20(12):1036–9. The efficacy of Silybum marianum (L.) Gaertn. (silymarin) in the treatment of type II diabetes: a randomized, double-blind, placebo-controlled, clinical trial. Huseini HF, Larijani B, Heshmat R, Fakhrzadeh H, Radjabipour B, Toliat T, Raza M.
23 Ann Pharmacother. 2012;46(10):1392–404. The use of galactogogues in the breastfeeding mother. Forinash AB, Yancey AM, Barnes KN, Myles TD.
24 Minerva Pediatr. 2014;66(5):375–80. Silymarin/galega administration in term and preterm mothers to sustain breast feeding: an observational study. Castoldi F, Pivetti V, Moiraghi L, Marangione P, Lista G.
25 Acta Biomed. 2008;79(3):205–10. Clinical efficacy, safety and tolerability of BIO-C (micronized Silymarin) as a galactagogue. Di Pierro F, Callegari A, Carotenuto D, Tapia MM.
26 World J Gastroenterol. 2011;17(18):2288–301. Silybin and the liver: from basic research to clinical practice. Loguercio C, Festi D.
27 Natl Toxicol Program Tech Rep Ser. 2011;(565):1–177. Toxicology and carcinogenesis studies of milk thistle extract (CAS No. 84604-20-6) in F344/N rats and B6C3F1 mice (Feed Studies). National Toxicology Program. Collaborators (45).
28 Toxicol Pathol. 2011;39(2):398–409. Investigating the potential for toxicity from long-term use of the herbal products, goldenseal and milk thistle. Dunnick JK, Singh B, Nyska A, Peckham J, Kissling GE, Sanders JM.
29 Integr Cancer Ther. 2007;6(2):146–57. Review of clinical trials evaluating safety and efficacy of milk thistle (Silybum marianum [L.] Gaertn.). Tamayo C, Diamond S.
30 Drugs. 2001;61(14):2035–63. The use of silymarin in the treatment of liver diseases. Saller R, Meier R, Brignoli R.
31 J Clin Pharmacol. 2010;50(4):434–49. Silymarin ascending multiple oral dosing phase I study in noncirrhotic patients with chronic hepatitis C. Hawke RL, Schrieber SJ, Soule TA, Wen Z, Smith PC, Reddy KR, Wahed AS, Belle SH, Afdhal NH, Navarro VJ, Berman J, Liu QY, Doo E, Fried MW; SyNCH Trial.
32 J Pharm Pharmacol. 2014;66(9):1339–46. The in-vitro effect of complementary and alternative medicines on cytochrome P450 2C9 activity. Mooiman KD, Goey AK, Huijbregts TJ, Maas-Bakker RF, Beijnen JH, Schellens JH, Meijerman I.
33 Drug Metab Dispos. 2013;41(9):1662–70. A systematic approach to evaluate herb-drug interaction mechanisms: investigation of milk thistle extracts and eight isolated constituents as CYP3A inhibitors. Brantley SJ, Graf TN, Oberlies NH, Paine MF.
34 Cancer. 2010;116(2):506–13. A randomized, controlled, double-blind, pilot study of milk thistle for the treatment of hepatotoxicity in childhood acute lymphoblastic leukemia (ALL). Ladas EJ, Kroll DJ, Oberlies NH, Cheng B, Ndao DH, Rheingold SR, Kelly KM.