Milk thistle has been shown to have antioxidant, anti-inflammatory, and antifibrotic effects, which form the basis for its use as a herbal supplement to aid in a variety of conditions.
What is Milk Thistle?
Milk thistle, also known as St. Mary’s thistle is a plant belonging to the daisy family, native to Mediterranean regions. The bioactive compounds in milk thistle are silymarin and silybin.
A large proportion of the research examining the benefits of milk thistle has focused on the extract of silymarin.
What are the claims?
Although traditionally used as a treatment for liver diseases, there are many other therapeutic claims for this herb, such as arthritis and melasma.
What are the scientific studies reporting? What is the evidence that milk thistle can be used as a herbal supplement?
Milk thistle for ulcerative colitis
A clinical trial assessing the effect of milk thistle in patients with ulcerative colitis found that supplementing with silymarin daily for a period of six months together with standard therapy was associated with a significant reduction in disease activity index compared with patients not taking silymarin.
In addition, more patients remained in complete remission with no flare-up if they were taking silymarin compared to those who were not taking the supplement.
The study concluded that silymarin may be useful in helping patients with ulcerative colitis to maintain remission.
Milk thistle for rheumatoid arthritis
In a clinical trial evaluating silymarin for changes in inflammatory markers associated with rheumatoid arthritis, patients were given silymarin in addition to standard treatment for inflammation.
The study reported significant reductions in the severity of disease activity, swelling, joint tenderness, and patient-reported pain.
It is important to note that this trial was a single-arm trial – meaning that there was only one treatment group and no comparison group.
Although these results are encouraging, further clinical research will be needed to confirm these results.
Milk thistle for acne
Due to the known antioxidant and anti-inflammatory properties of silymarin, it has also been tested as a treatment for acne.
A clinical trial tested the effectiveness of silymarin both alone and in combination with doxycycline – an oral medication for acne. The study tested three treatment groups – silymarin or doxycycline alone, and silymarin and doxycycline combined.
Acne severity was graded in each participant at monthly intervals. There was no significant difference reported between participants who were taking silymarin compared to those taking doxycycline.
The study reported better results for the combination treatment group, although it was not a statistically significant difference.
This suggests that silymarin could be a useful treatment for acne, potentially in combination with other treatments.
Milk thistle for vitiligo
A clinical trial investigated combining phototherapy with a silymarin supplement as a treatment strategy for vitiligo.
This was a relatively small trial, including only 34 participants.
The participants were evaluated for severity of vitiligo and then split into two groups – one group received a silymarin supplement and the other group did not. All participants were also treated with phototherapy.
The severity of vitiligo was significantly reduced in patients from both groups, however, to a greater extent in the group that was also receiving the supplement.
The study suggests that silymarin may be a good treatment option for patients with vitiligo, however, due to the size of the study, this should be confirmed in larger clinical trials.
Milk thistle for allergies
Silymarin has also been investigated in people with allergic rhinitis due to its known protective effects against oxidative stress.
In a randomized clinical trial, patients with allergic rhinitis were given either silymarin or a placebo together with the usual antihistamine. The effects on levels of markers of allergic rhinitis were assessed.
The study found that improvements in the severity of allergic rhinitis were seen in both groups, however to a greater extent in the group taking the silymarin.
The researchers concluded that silymarin may be useful in helping to manage symptoms of allergic rhinitis.
Milk thistle for melasma
Milk thistle silymarin cream has also been investigated as a topical treatment for melasma – a condition associated with dark patches of skin, typically on the face.
A clinical study assessed the safety and effectiveness of milk thistle for treating melasma.
In the first part of the study, researchers treated albino rabbits with silymarin cream prior to sun exposure. These rabbits were compared with rabbits who either had no treatment or a placebo treatment.
In the second part of the study, patients with melasma applied the cream each day for a one-month period. The researchers found that milk thistle silymarin improved melasma, specifically, pigmentation and size.
The differences were noticed within the first week of treatment and were not associated with any side effects.
The researchers suggest that silymarin is a “safe new candidate effective treatment for melasma.”
Milk thistle for type 2 diabetes
In a study including forty patients with type 2 diabetes, silymarin was assessed for its effect on blood glucose levels. Twenty participants were given the supplement and compared to another twenty patients who were given a placebo.
Compared to placebo, the study reported a significant decrease in fasting blood sugar and serum insulin levels in patients who were taking silymarin.
In addition to this, the study found an increase in HDL – ‘good cholesterol’ – and an increase in insulin sensitivity check index in patients taking silymarin.
Taking silymarin was also associated with a significant reduction in total cholesterol and LDL concentrations.
In another clinical trial, participants with type 2 diabetes were given a herbal supplement containing milk thistle and compared with patients given a placebo.
In this study, participants taking the supplement for a three-month period were found to have significant reductions in fasting blood glucose, glycosylated hemoglobin, and triglyceride levels compared with participants taking the placebo.
Are there any side effects from taking milk thistle?
Side effects from taking milk thistle are typically uncommon but can include diarrhea, headache, hives, or rash.
Although there are currently no contraindications listed for milk thistle, it is still important to speak with your healthcare provider before taking any herbal supplements, particularly if you have an underlying health condition or are taking any medications.
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