On The Shelf
Mickie Cathers
Recent studies have shown an increase in alcohol-related digestive and liver diseases as alcohol consumption grew during the COVID-19 pandemic. Patients may embrace milk thistle—which has been promoted as a dietary supplement for hepatitis, cirrhosis, jaundice, diabetes, and indigestion—to protect the liver from environmental toxins. With hundreds of years of history as treatment for a wide range of liver disorders and gallbladder problems, milk thistle has become increasingly popular as a support for healthy liver function.
Background and function
Milk thistle (Silybum marianum, L. Gaertn.), sometimes called wild artichoke, is an annual to biennial plant that flowers in July and August. Milk thistle resembles a seed but is technically a fruit with red-purple flowers and milky-white veins in the leaves.
Since the 1970s, researchers have shown that milk thistle’s hepatoprotective properties are attributed to its antioxidant, anti-inflammatory, and antifibrotic assets. Milk thistle’s benefits derive from silymarin and silybin. Silybin belongs to the flavonoid group called flavonolignans, which have strong antioxidant properties that reduce proinflammatory mediators through modulation of a variety of cell-signaling pathways.
Silymarin has been shown to down-regulate and inhibit the expression of COX-2, a key mediator of inflammatory pathways. Silymarin also inhibits the transduction cascade controlled by NF-kB, a protein complex that induces expression of proinflammatory genes responsible for encoding cytokines that are directly involved in the inflammatory process. NF-kB also regulates the survival of inflammatory T cells.
Milk thistle’s antioxidant benefits result from its ability to inhibit free radicals derived from the metabolism of toxic substances such as ethanol, acetaminophen, and carbon tetrachloride. It stimulates protein synthesis by protecting cell membranes from free radical-induced damage and directly inhibiting radical formation. It can also act as a free radical scavenger and increase the intracellular content of these scavengers.
In addition to anti-inflammatory and antioxidant properties, milk thistle may also serve as an antifibrotic agent. Silybin has been shown to decrease platelet-derived growth factor–induced DNA synthesis in cells, which inhibits the transformation of stellate hepatocytes into myofibroblasts. Silybin decreases myofibroblasts and thereby indirectly prevents the deposition of collagen fibers that lead to liver injury progression. Studies have demonstrated that silybin is associated with a significant reduction of TGF-B, a key regulator in the pathogenesis of liver fibrosis.
Is there a benefit?
A 2020 review in Advances in Therapy by Gillessen and Schmidt highlighted clinical studies in patients with alcoholic or nonalcoholic fatty liver disease, including patients with cirrhosis, and found that milk thistle treatment was associated with a significant reduction in liver-related deaths.
A 12-month clinical trial by Velussi et al. in the Journal of Hepatology indicated that silymarin treatment correlated with a reduction in insulin resistance and a significant decrease in fasting insulin levels. Insulin-treated patients with both diabetes and alcoholic liver cirrhosis were given 600 mg/day of silymarin for 12 months or standard therapy.
Efficacy parameters included fasting blood glucose levels, mean daily blood glucose levels, daily glucosuria levels, glycosylated hemoglobin, and malondialdehyde levels. Results showed a significant decrease in fasting insulin levels after 4 months for the silymarin group. In comparison, the control group showed a significant increase in fasting insulin levels.
Daily requirements and dietary sources
Milk thistle is available as a capsule, tablet, liquid extract, and tea. Milk thistle supplements are available in stores, groceries, and online, and are tolerated with no adverse effects at doses of up to 700 mg/day.
What to tell your patients
Milk thistle is recognized as a safe herbal product and appears to be well-tolerated in recommended doses. Although rare, some adverse effects include gastroenteritis, diarrhea, headache, or dermatological reactions, which are more common among those allergic to plants in the same family (e.g., ragweed, chrysanthemum, marigold, and daisy). Milk thistle should not be used by pregnant or breastfeeding patients.