The Ultimate Guide To Milk Thistle: Scientific Evidence and Potential Health Benefits

Milk thistle (Silybum marianum) is a flowering herb that has been used for centuries in traditional medicine, particularly for liver health. The active compound in milk thistle, known as silymarin, is a complex of flavonolignans that has garnered significant scientific interest due to its potential health benefits. This article will explore the various ways milk thistle and silymarin may contribute to human health, drawing from current scientific research.

Liver Health

The most well-known and studied benefit of milk thistle is its potential to support liver health. Silymarin has been shown to have hepatoprotective properties, meaning it may help protect liver cells from damage.

Alcoholic Liver Cirrhosis

One study found that silymarin supplementation in alcoholics significantly improved liver function tests. This was evident through the normalization of serum transaminases AST and ALT.(1)  A human clinical trial done on patients with alcoholic cirrhosis showed that patients taking milk thistle daily had longer survival and less chance of death due to alcoholic cirrhosis complications.(2)  Another study actually biopsied the livers of patients after they had been randomized to milk thistle vs a placebo.  Those who were taking milk thistle saw histological improvements in their livers, and a decreases in procollagen III peptides suggesting decrease liver fibrosis.(3)

Non-alcoholic Fatty Liver Disease

In cases of non-alcoholic fatty liver disease (NAFLD), a condition increasingly common in Western countries, milk thistle has shown promise. A randomized controlled trial demonstrated that patients with NAFLD who took silymarin experienced significant improvements in liver enzymes and insulin resistance compared to those who received a placebo.(4) More studies have confirmed this liver function normalizing effect of silymarin. (5)

Viral Hepatitis

Furthermore, milk thistle may have potential in treating viral hepatitis. In a clinical trial in patients with acute viral hepatitis, those given milk thistle had a quicker recovery than those given placebo.(6) In patients with chronic hepatitis C, silymarin reduced the progression of liver fibrosis to cirrhosis. (7)

Antioxidant Properties

One of the primary mechanisms by which milk thistle exerts its beneficial effects is through its potent antioxidant properties. Silymarin has been shown to scavenge free radicals and reduce oxidative stress in various tissues. A study published in the journal Burns, demonstrated that silymarin protected against oxidative stress-induced cellular damage in human skin fibroblasts. This suggests potential applications in protecting against skin aging and oxidative damage. (8)

Anti-inflammatory Effects

Chronic inflammation is associated with numerous health problems, including cardiovascular disease, diabetes, and certain cancers. Milk thistle has demonstrated anti-inflammatory properties in several studies. In a human clinical trial, silymarin was actually able to induce remission in 35 out of 38 patients with ulcerative colitis. While more human studies are needed, this suggests potential applications in managing inflammatory bowel diseases. (9)

Diabetes Management

Emerging research indicates that milk thistle may have benefits for individuals with diabetes. A randomized controlled trial found that silymarin supplementation improved glycemic control and lipid profiles in patients with type 2 diabetes. The study showed significant reductions in fasting blood glucose, HbA1c, and total cholesterol levels in the silymarin group compared to the placebo group. These findings suggest that milk thistle could be a valuable adjunct therapy in diabetes management. (10)

Cardiovascular Health

The antioxidant and anti-inflammatory properties of milk thistle may also contribute to cardiovascular health. An interventional animal study demonstrated that silymarin protected against ischemia-reperfusion injury in rat hearts.(11) Additionally, the improvements in lipid profiles observed in diabetic patients suggest potential cardiovascular benefits. However, more research is needed to fully understand milk thistle's effects on heart health in humans.

Cancer Prevention and Treatment

While research is still in early stages, some studies suggest that milk thistle may have anticancer properties. A 2006 review highlighted silymarin's potential in cancer prevention and treatment. The review noted that silymarin has shown anticarcinogenic effects in various cancer cell lines, including breast, prostate, and skin cancer.(12) It may work by inhibiting cell proliferation, inducing apoptosis (programmed cell death), and reducing angiogenesis (formation of new blood vessels).

However, it's important to note that most of these studies have been conducted in vitro or in animal models. More human clinical trials are needed to confirm milk thistle's efficacy in cancer prevention and treatment.

Brain Health

Emerging research suggests that milk thistle may have neuroprotective properties. A study published in Toxicology found that silymarin protected against oxidative stress and inflammation in a model of Parkinson's disease.(13)  Another study demonstrated that silymarin improved cognitive function in rats that had cognitive decline due to diabetes.(14) While these results are promising, human studies are needed to confirm these effects.

Skin Health

The antioxidant properties of milk thistle may also benefit skin health. A study showed that topical application of silymarin protected against UV-induced skin damage (15). Furthermore, a clinical trial found that a silymarin-based cream improved symptoms of rosacea in human subjects.(16) These findings suggest potential applications in skincare and dermatology.

Safety and Side Effects

Milk thistle is generally considered safe for most people when taken orally. However, some individuals may experience side effects such as gastrointestinal upset, headaches, or allergic reactions. A systematic review concluded that milk thistle has a good safety profile, with only minor, self-limiting side effects reported in clinical trials.(17)  However, milk thistle may interact with certain medications, particularly those metabolized by the liver. This doesn't prevent you from taking milk thistle, but it's important to consult with a healthcare provider before starting milk thistle supplementation if you are taking pharmaceuticals drugs.  Here is a list of potential interactions of milk thistle with precription medications.

Conclusion

Milk thistle and its active compound silymarin show promise in supporting various aspects of human health, particularly liver function. Its antioxidant and anti-inflammatory properties may contribute to its potential benefits in diabetes management, cardiovascular health, cancer prevention, neurological health, and skin protection.

While many studies have shown positive results, it's important to note that much of the research is still in early stages, particularly for applications beyond liver health. More large-scale human clinical trials are needed to fully understand the efficacy and optimal dosing of milk thistle for various health conditions.

As with any supplement, individuals should consult with a healthcare provider before adding milk thistle to their regimen if they have existing health conditions or are taking medications. While milk thistle shows promise as a natural health aid, it should not be considered a replacement for conventional medical treatments.

The growing body of research on milk thistle and silymarin is encouraging, and future studies may uncover even more potential health benefits. As our understanding of this herb grows, it may become an increasingly valuable tool in promoting human health and managing various medical conditions.

References

1. Salmi, H. A., and S. Sarna. "Effect of silymarin on chemical, functional, and morphological alterations of the liver: a double-blind controlled study." Scandinavian journal of gastroenterology 17.4 (1982): 517-521.
2. Ferenci, P., et al. "Randomized controlled trial of silymarin treatment in patients with cirrhosis of the liver." Journal of hepatology 9.1 (1989): 105-113.
3. Feher, J., et al. "Liver-protective action of silymarin therapy in chronic alcoholic liver diseases." Orvosi hetilap 130.51 (1989): 2723-2727.
4. Hashemi, Seyed Jalal, Eskandar Hajiani, and SARDABI E. HEYDARI. "A placebo-controlled trial of silymarin in patients with nonalcoholic fatty liver disease." (2009): 265-270.
5. Kalopitas, Georgios, et al. "Impact of Silymarin in individuals with nonalcoholic fatty liver disease: A systematic review and meta-analysis." Nutrition 83 (2021): 111092.
6. Magliulo, E., B. Gagliardi, and G. P. Fiori. "Results of a double blind study on the effect of silymarin in the treatment of acute viral hepatitis, carried out at two medical centres (author's transl)." Medizinische klinik 73.28-29 (1978): 1060-1065.
7. Freedman, N. D., et al. "Silymarin use and liver disease progression in the Hepatitis C Antiviral Long‐Term Treatment against Cirrhosis trial." Alimentary pharmacology & therapeutics 33.1 (2011): 127-137.
8. Svobodová, Alena, Daniela Walterová, and Jitka Psotová. "Influence of silymarin and its flavonolignans on H2O2-induced oxidative stress in human keratinocytes and mouse fibroblasts." Burns 32.8 (2006): 973-979.
9. Rastegarpanah, Mansoor, et al. "A randomized, double blinded, placebo-controlled clinical trial of silymarin in ulcerative colitis." Chinese journal of integrative medicine 21 (2015): 902-906.
10. Elgarf, Amany Talaat, Maram Maher Mahdy, and Nagwa Ali Sabri. "Effect of silymarin supplementation on glycemic control, lipid profile and insulin resistance in patients with type 2 diabetes mellitus." Int. J. Adv. Res 3 (2015): 812-821.
11. Zalat, Zeinab, et al. "Silymarin: A promising cardioprotective agent." Azhar International Journal of Pharmaceutical and Medical Sciences 1.1 (2021): 13-21.
12. Agarwal, Rajesh, et al. "Anticancer potential of silymarin: from bench to bed side." Anticancer research 26.6B (2006): 4457-4498.
13. Pérez-H, Jesús, et al. "Neuroprotective effect of silymarin in a MPTP mouse model of Parkinson's disease." Toxicology 319 (2014): 38-43.
14. Yön, Burcu, Muaz Belviranlı, and Nilsel Okudan. "The effect of silymarin supplementation on cognitive impairment induced by diabetes in rats." Journal of Basic and Clinical Physiology and Pharmacology 30.4 (2019): 20180109.
15. Svobodová, Alena, et al. "Attenuation of UVA-induced damage to human keratinocytes by silymarin." Journal of dermatological science 46.1 (2007): 21-30.
16. Berardesca, Enzo, et al. "Combined effects of silymarin and methylsulfonylmethane in the management of rosacea: clinical and instrumental evaluation." Journal of cosmetic dermatology 7.1 (2008): 8-14.
17. Soleimani, Vahid, et al. "Safety and toxicity of silymarin, the major constituent of milk thistle extract: An updated review." Phytotherapy research 33.6 (2019): 1627-1638.