Why athletes need silymarin
Silymarin is one of the most popular supplements in gyms: it is bought "for the liver" during cutting, on a high-protein diet, and among users of anabolic steroids as a mandatory "protection". The editors have looked into whether athletes have real reasons to worry about the liver, what is known about silymarin in this context, and where the evidence ends and marketing promises begin.
The athlete's liver: what strains it
The healthy liver of a person who trains regularly usually needs no "protection" at all. Moderate physical activity, on the contrary, is good for the liver: it reduces fat deposition in hepatocytes, improves insulin sensitivity and lowers the risk of non-alcoholic fatty liver disease.
Problems arise where other factors are added to training. Among them are alcohol, excess calories and obesity in strength sports, uncontrolled use of painkillers (paracetamol in high doses), and also supplements of dubious quality, in particular "fat burners" with plant extracts, which have repeatedly caused drug-induced liver injuries.
A separate and most serious risk group is the use of anabolic androgenic steroids, primarily oral 17-alpha-alkylated drugs. It is precisely these that are most often associated with cholestasis, peliosis of the liver and liver tumors in athletes.
High-protein diets by themselves do not cause damage to a healthy liver. The popular myth that "protein wrecks the liver" is not confirmed by research; it is another matter for people with already existing liver or kidney diseases, whose diet is chosen by a doctor.
| Factor | Effect on the liver | Will silymarin help |
|---|---|---|
| Regular training | Mostly beneficial | Not needed |
| High-protein diet in a healthy person | No evidence of harm | Not needed |
| Alcohol | Direct hepatotoxicity | Does not compensate for the harm |
| Poor-quality "fat burners" | Risk of drug-induced injury | Does not protect; better to avoid |
| Oral anabolic steroids | Cholestasis, peliosis, tumors | No evidence of protection |
"Bad" liver tests after workouts
One common reason why athletes start taking silymarin is elevated ALT and AST in a biochemical test. However, these enzymes are found not only in the liver but also in muscles. Intense strength training, especially with new exercises or high volume, can raise AST and even ALT for several days.
This was well demonstrated by the work of Pettersson et al., published in 2008 in the British Journal of Clinical Pharmacology. Healthy men who did not train with weights regularly had, after a single intense session, a significant rise in AST, ALT, creatine kinase and LDH that persisted for up to a week. The authors emphasized: such changes can be mistaken for drug-induced liver injury.
Additional indicators help to distinguish a muscular source from a hepatic one. Creatine kinase (CK) rises sharply with muscle damage, while gamma-glutamyl transferase (GGT) and bilirubin are indicators that usually do not change with muscle exertion. Normal GGT with high ALT/AST and high CK points to a muscular cause.
Hence the practical advice: liver tests should be taken after 5–7 days without intense training, together with CK and GGT. This helps to avoid false alarm and unnecessary intake of "hepatoprotectors".
If, however, the elevation is confirmed repeatedly during rest, silymarin is not the answer. It is necessary to find out the cause — viral hepatitis, fatty liver disease, alcohol, drugs or supplements — and for this to see a doctor.
Silymarin and anabolic steroids
Among users of anabolic steroids, silymarin is often considered a mandatory "companion". The editors emphasize: there are no clinical studies that have shown silymarin to prevent cholestasis, peliosis or liver tumors associated with oral 17-alpha-alkylated steroids. The notion of "protection" is based on extrapolation of laboratory data.
The mechanism of liver damage from such substances involves disruption of bile acid transport and hormonally mediated changes in the liver's vessels. The antioxidant action of silymarin does not directly eliminate these mechanisms. Therefore, even if the supplement somewhat improves individual indicators, it does not neutralize the risk of serious complications.
The danger also lies in a false sense of security. A person taking a "protective" supplement tends to ignore early symptoms — itching of the skin, darkening of the urine, yellowing of the sclera, discomfort in the right upper abdomen — and to postpone examination. Cholestatic liver damage can be severe and prolonged.
We also recall that the use of anabolic steroids without medical indications is associated with many risks beyond the liver: for the heart, blood vessels, hormonal system and psyche. No "hepatoprotector" makes such use safe. Anabolic steroids are included in the WADA Prohibited List, while silymarin itself is not a prohibited substance.
What research in active people shows
There are few studies of silymarin specifically in athletes, and these are mostly small works that examined markers of oxidative stress or muscle damage after exertion. Some of them reported a reduction in individual markers, but the samples were small and the results inconsistent. It is not possible to speak confidently about improved recovery or performance.
A broader evidence base concerns patients with liver diseases. The Cochrane review by Rambaldi, Jacobs and Gluud found no convincing effect of milk thistle on mortality or complications in alcoholic and viral liver diseases, although it did note good tolerability. Large randomized trials in hepatitis C also showed no benefit.
Somewhat more encouraging data concern non-alcoholic fatty liver disease: in the randomized trial by Wah Kheong et al. (2017), silymarin did not reach the primary endpoint, but on secondary indicators a reduction in fibrosis was observed. For athletes who are overweight and have fatty liver disease these data may be of interest, but the main treatment remains weight reduction and physical activity.
The conclusion for active people is this: silymarin is well tolerated, but there is insufficient evidence that it improves athletic performance or recovery or "protects" a healthy liver. Expectations of the supplement should be moderate.
A rational approach to taking it
If an athlete nevertheless decides to take silymarin as a dietary supplement, it is worth following a few principles. In clinical studies the most commonly used was a standardized extract at a dose of 140 mg of silymarin three times a day (about 420 mg a day); forms with phosphatidylcholine have higher bioavailability and are often used in smaller doses.
- Choose a product with standardization by silymarin content and reliable quality control.
- Do not use silymarin as an excuse for alcohol, poor-quality "fat burners" or steroids.
- Have liver tests done after several days of rest, together with CK and GGT.
- In case of persistent test abnormalities, see a doctor rather than increasing the dose of the supplement.
- Tell your doctor about taking silymarin if you are taking other drugs.
The most effective ways to support the liver of an active person are well known: moderation with alcohol, control of body weight and body fat percentage, avoidance of dubious supplements, sensible use of painkillers and vaccination against hepatitis B.
People with already diagnosed liver diseases should make the decision about taking silymarin together with a hepatologist, since it can affect the metabolism of some drugs.
Editorial conclusions
The healthy liver of a person who trains usually needs no "protection"; moderate physical activity is itself good for it.
Elevated ALT and AST after workouts often have a muscular origin — it is important to take the tests correctly and to assess CK and GGT.
Silymarin is well tolerated, but there is no evidence that it prevents liver damage from anabolic steroids or improves athletic performance.
We also recommend reading our articles "Silymarin: mechanism of action", "Side effects and contraindications of silymarin" and "NAC or silymarin: what is the difference".
References
- Pettersson J, Hindorf U, Persson P, et al. Muscular exercise can cause highly pathological liver function tests in healthy men. Br J Clin Pharmacol. 2008;65(2):253–259.
- Rambaldi A, Jacobs BP, Gluud C. Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev. 2007;(4):CD003620.
- Wah Kheong C, Nik Mustapha NR, Mahadeva S. A randomized trial of silymarin for the treatment of nonalcoholic steatohepatitis. Clin Gastroenterol Hepatol. 2017;15(12):1940–1949.
- Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Androgenic Steroids. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases.
- Saller R, Meier R, Brignoli R. The use of silymarin in the treatment of liver diseases. Drugs. 2001;61(14):2035–2063.
- World Anti-Doping Agency. The World Anti-Doping Code: International Standard — Prohibited List. Montreal: WADA; 2024.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
