Milk thistle supports liver function

Photo: Wikipedia

The milk thistle, or Silybum marianum, plant.

Milk thistle has been used in folk medicine to treat liver disorders, kidney disease, bile congestion, high cholesterol, stimulate milk production, help diabetes and blood sugar irregularities, treat skin disorders and acne, act as an antioxidant, provide an adjunctive cancer benefit, support healthy bones and help ease digestive and stomach ailments.

In the 18th century, it was the treatment of choice for liver disorders. The leaves, seeds and fruit have all been used for medicinal purposes.

Milk thistle or Silybum marianum, grows from one to three metres high and has large prickly leaves and purple and red flowers. It is indigenous to Asia and is also found in Europe and North America, from Canada to Mexico. The ancient Greeks used the plant medicinally and named it “silybum” meaning thistle. During the Middle Ages, monks introduced the plant to Europe and regarded it with mythical and religious adoration.

The crude extract obtained from milk thistle was originally termed “silymarin.” Silymarin represents a mixture of flavonoid compounds called flavonolignans. While those flavonoids are found in the leaves and fruit, they are found in highest concentration in the ripe seeds. The seeds contain 4% to 6.% silymarin, which has been identified as the active ingredient in milk thistle responsible for its purported medicinal effects.

Concentrated extracts standardized to contain 70% to 80% silymarin content have been developed.

Mulrow et al reviewed 11 medical databases and identified 16 prospective studies that were identified with 14 randomized, placebo-controlled trials of milk thistle in liver disease. Also, 16 additional non-placebo-controlled trials were analyzed. Four studies reported significant improvement in at least one measurable liver function. Three studies of unspecified liver etiology showed improvement in at least one liver function marker compared to the placebo. Two studies showed an overall decrease in mortality and three placebo-controlled double-blind trials of 28-day durations in patients with viral hepatitis showed significant improvement in multiple parameters.

A longer duration study of up to one year showed a consistent decrease in liver enzyme levels. Two trials involving patients with alcoholic cirrhosis showed a non-significant improvement in liver function, hepatocytes, jaundice, ascites and swelling. Also, another study of 30-day duration, showed a significant improvement in liver enzyme levels compared to placebo.

A pooled meta-analysis review of those studies concluded clinical efficacy of milk thistle in the treatment of liver disease was not clearly established despite improvements that some individual studies showed. Most of the benefit reported appeared to be related to a decrease in liver enzyme levels. The mechanism of action of milk thistle was not clearly identified or established in most studies and was surmised to be multifactorial. More good quality trials were recommended to fill in the gaps that this meta-analysis identified.

Jacobs et al searched 13 databases and identified 14 studies that met their inclusion criteria. Three studies showed an inverse relationship between histologic benefit and milk thistle compared to placebo. No difference in liver enzymes, including ALT, AST, albumin and prothrombin levels, was found between milk thistle and a placebo.

The only statistically significant improvement noted was a consistent decrease in ALT enzyme levels compared to placebo. The researchers concluded there was no reduction of mortality, improvement in histology of liver biopsy or biochemical markers of liver function. The overall efficacy of milk thistle remained inconclusive.

Ribeiro de Avalar et al conducted a systematic review with meta-analysis of randomized controlled trials of the effects of milk thistle on liver disease. Seventeen studies of the 10,904 searched on electronic databases met inclusion criteria. Six of those studies were included in the meta-analysis. A small but statistically significant decrease in liver was observed. The researchers noted that there was a high degree of heterogeneity and low methodological quality in the studies analyzed.

Milk thistle is generally a neutral and safe natural liver medicine that can help support liver function and aid in digestion. Side effects reported included gastro-intestinal problems including diarrhea, gas, bloating and a change in bowel habits, headache, eczema, pruritus, fatigue, arthralgia and itchy eyes.

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