Uncovering the hidden benefits of versatile milk thistle

The standardized extract from the seeds of the milk thistle (Silybum marianum) is probably the best-proven herb for protecting the liver from chemical and inflammatory damage. The herb has been found to be beneficial for a wide range of liver disorders, including hepatitis and cirrhosis.1 But the extract, (typically – and perhaps inaccurately – called silymarin or silymarin extract) has also revealed some intriguing outcomes in other clinical studies. These surprising results show a wide clinical versatility for the herb. So it’s important to not think of this extract as only being beneficial for the liver. Read on to discover some valuable new insights into the healing power of this amazing herb.

Clinically proven to fight allergies and inflammation

In a double-blind trial, 94 patients suffering the signs and symptoms of allergic rhinitis (hay fever) and exhibiting positive skin prick tests to common aeroallergens randomly received either silymarin extract (420 mg/day) or a placebo for one month.2 Routine antihistamine treatment was also allowed. Based on the Sino-Nasal Outcome Test (SNOT-20!), an improvement in clinical symptom severity was observed in both groups, but the improvement was significantly greater in the herbal group (9.2 for the silymarin group versus only 2.2 for the placebo group).

In a 2009-published double-blind clinical trial, 220 patients with painful knee osteoarthritis (OA) were randomly divided into five groups, receiving either silymarin (300mg/ day), piroxicam (20mg/day), meloxicam (15mg/day) or a combination of silymarin with each of the anti-inflammatory drugs.3 There was no placebo group in the study design and treatment was over eight weeks. Treatment with silymarin significantly reduced serum levels of the inflammatory cytokines interleukin (IL)-1alpha (by 56%) and IL-8 (by 58%) (p < 0.02 compared with baseline), and the complement proteins C3 (by 81%) and C4 (by 45%). Adjunct use of silymarin with the drugs gave mixed results for these measures of inflammation (no effect with meloxicam and a significant lowering with piroxicam). The drugs on their own generally exhibited minimal beneficial or even adverse effects. Unfortunately, the trial did not provide data for clinical OA symptoms. An earlier study also demonstrated that co-administered silymarin decreased the renal and hepatic toxicities of these drugs in OA patients.4

Although these uses might seem novel for silymarin, they are consistent with several lab studies demonstrating various anti-inflammatory, antiallergic and immune-modulating outcomes for the herbal extract. However, results from experimental models don’t necessarily reflect clinical outcomes for herbal treatments, so the above clinical findings do add significant credibility to the use of silymarin for allergic rhinitis (and perhaps other allergies) and OA. More studies are needed, however, especially one assessing clinical outcomes in OA. 

Makes mothers’ milk flow better

One surprising new role for the silymarin extract is its use to enhance milk production in healthy breastfeeding mothers. Following an agricultural trial demonstrating that silymarin promoted milk production in dairy cows, a group of Italian scientists investigated its galactagogue (enhancing milk flow) value in humans.5 The trial enrolled 50 healthy lactating women who received a daily dose of 420mg of micronized (very fine) silymarin or an identical placebo for 63 days. At both days 30 and 63 of the trial there was a clear and significant difference over placebo in favour of the silymarin group in terms of total milk production (p < 0.01). There also appeared to be a cumulative treatment effect, with a 64.4% increase above baseline at day 30 for the silymarin group (versus 22.5% for placebo), which increased to 86.0% by day 63 (versus 32.1% for the placebo). Analysis of the nutritional value (water, fats, carbohydrates and proteins) of the milk confirmed no difference between the active and placebo groups. Testing of the milk from a smaller group of women who received 1,800mg/ day silymarin for five days found no detectable levels of silymarin actives, indicating no issue for the baby.

Given the common name of milk thistle, you may wonder why it would be surprising to learn of its ability to enhance milk flow. The answer is that the most likely source of this common name is the actual appearance of the plant, not any traditional use for milk flow. Specifically, the white stripes on the leaves are said to represent the milk of the Virgin Mary.6,7 There’s no reference to any milk-flow enhancing action in texts reflecting traditional use, such as the British Herbal Compendium.8 The authors of another paper on the topic claim that the book of Newall and co-workers carries a reference to galactagogue use. However, the information wasn’t found on the pages cited, or anywhere else in the book. Perhaps this confusion serendipitously led to its discovery, or maybe this is a previously unrecognized example of the doctrine of signatures (in which the appearance of a herb suggests its therapeutic activity). The well-known book A Modern Herbal by Maude Grieve does talk about this herb enhancing milk flow, but she is clearly referring to the use of the leaves not an extract of the seeds.

A lab study has provided a possible mechanism behind the herb’s ability to enhance milk flow.11 A dose-dependent increase in prolactin levels was seen in female rats after 25 to 200mg/kg were administered orally for 14 days. For 66 days after the herbal extract was discontinued prolactin levels remained raised. The drug bromocriptine antagonized the prolactin-inducing activity of silymarin extract, suggesting that dopamine D2 receptors are involved. Such hormonal effects need to be investigated in lactating women.

To your better health,

Kerry Bone
Nutrition & Healing

Vol. 9, Issue 1 • January 2015


Full references and citations for this article are available in the downloadable PDF version of the monthly Nutrition and Healing issue in which this article appears.

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