Milk thistle is associated with several health benefits, but that doesn’t mean just taking any milk thistle supplement in any amount will reveal these advantages. The bioavailability of milk thistle is particularly low. Meaning, you may only be metabolizing (and getting the benefits) from just 1% of the amount you take. As with most natural medicines, dosage and timing are key. Lastly, if you are using milk thistle for your skin, you may be better off with a topical application instead of a supplement.
Table of Contents
- 3-Point Guide to Using Milk Thistle
- What kind of milk thistle to take, orally?
- How much milk thistle to take?
- The bottom line
3-Point Guide to Using Milk Thistle
The biggest challenge with milk thistle is that its most important, active ingredients are limited in their bioavailability. That means that even if you are taking a milk thistle supplement, only a small fraction, as little as half a percent, may be metabolized.
Here, we focus our buying guide for those interested in using milk thistle to improve health, but not to treat any serious conditions. Not only is it imperative to consult with a health care provider for serious conditions, but the evidence for the use of milk thistle is limited to certain derivatives and concentrations. For example, in the case of liver disease, the evidence is based on well-standardized extracts, often administered intravenously (not capsules). These are serious, pharmaceutical-grade formulations. Like Legalon® SIL, a formulation manufactured in Germany, and used to treat intoxication from death cap mushrooms [Mengs 2012].
Nonetheless, if you want to use milk thistle to improve your skin health or your overall health, then consider the following guidelines:
- Topical or oral? If you are using milk thistle for a skin condition, opt for a topical application. If you are using it to support your health, then go with a supplement.
- Supplements: 140mg 2-3 times a day is a standard dose in many studies. Look for capsules that are micronized, made of soft gelatine and/or with added phosphatidylcholin, β-cyclodextrin or hydroxypropyl-β-cyclodextrin (HP-β-CyD) to help absorption.
- Topical: Use 7mg/ml, 14mg/ml, 0.25% or 1% concentrated silymarin creams twice daily.
What kind of milk thistle to take, orally?
The biggest challenge with milk thistle is its low bioavailability. The bioavailability generally relies on two main factors: the accompanying substances (such as phenolderivatives, amino acids, proteins, etc. found in the extract) and the concentration of the extract itself [Saller 2012].
Look for silymarin or silibinin supplements with the following characteristics:
- Added phosphatidylcholin [Morazzoni 1992] or β-cyclodextrin [Ghosh 2011] or hydroxypropyl-β-cyclodextrin [Onodera 2022]
- Micronized; a procedure which improves the bioavailability [Di Pierro 2008].
- Added solubilizing substances to the extract [Saller 2012]
- Using the soft gelatine capsule material [Savio 1998]
The content specifications or guarantee of nutrition on a milk thistle supplement don’t guarantee bioavailability.
Researchers evaluate the bioavailability of milk thistle supplements by measure the plasma concentrations. Although silymarin’s main site of action is the liver, systemic plasma provides a better estimate of how much silymarin is absorbed in the GI tract.
How much milk thistle to take?
140mg of silymarin 2-3 times daily for 8 weeks or more, is a common dosage used in studies evaluating the effectiveness of silymarin for serious conditions. For use as a galactagogue, 420mg/day of micronized milk thistle for 30 days was found to be effective.
There are dozens of studies evaluating milk thistle for a range of conditions. Among them, dosage and duration range widely, and so careful consideration and consultation with a professional is vital before using milk thistle for any serious condition [Soleimani 2019].
In order to determine guidelines for taking milk thistle as just an ordinary supplement, to support general health, we extrapolate the treatments generally used in clinical trials. The most common dosing (used in about a dozen studies) is 140mg 2-3 times daily.
However, other doses may be also be effective. For treatment in liver diseases, the dosage is generally higher and over the course of several months. For example, 420mg/day for 6 months appeared to demonstrate some beneficial activity for patients with chronic alcoholic liver disease [Saller 2012]. Another study found that patients treated with 140mg three times a day for about 41 months survived their cirrhosis longer than those in the placebo group [Ferenci 1989]. In the treatment of diabetes, 140mg three times daily for three months was found to potentially help with diabetic kidney disease [Fallahzadeh 2012].
As for its use as a way to stimulate milk-production, one study found that women given 420 mg/day of micronized silymarin had significantly higher milk production after 30 days than those given placebo [Di Pierro 2008].
What kind of milk thistle to use, topically?
Studies generally use 7mg/ml, 14mg/ml, 0.25% or 1% concentrated silymarin creams. Although studies use these for skin conditions resulting from lab-induced radiation, or melasma, we may use this as a guideline for using milk thistle for skin protection in general.
Researchers are optimistic that silymarin, used in conjunction with sunscreen, may provide better, full-spectrum protection against sunlight. Its anti-inflammatory, antioxidant, and anti-carcinogenic properties, as well as its minimal side-effects and lack of toxicity, make silymarin a promising method to prevent skin conditions [Katiyar 2005].
Studies evaluating the effectiveness of silymarin cream use it in the treatment of melasma and as a way to prevent skin conditions resulting from radiation (chemotherapy or the like). There are no studies that can yet inform us on how to use silymarin for skin protection from UV-radiation, but we may extrapolate these findings and attempt to apply them for regular use of milk thistle as a way to better protect the skin from sun exposure.
Topical studies
Unfortunately, not all studies provide details of the type of silymarin extract used. [Katiyar 1997], [Katiyar 2002], and [Bhatia 1999] use silymarin and/or silibinin sourced from chemical companies. In the case of topical application, the silymarin was diluted in acetone. However, the three studies below do provide details of the concentration of the creams.
[Altaei 2012] conducted a double-blind randomized trial on patients with melasma, who had it for 2-6 years already (and a significant portion of which had melasma in their family history). Melasma is a skin condition characterized by grey-brown patches of discoloration on the face. Patients received either 7mg/ml cream, 14mg/ml cream, or placebo, applied twice daily for 4 weeks. They were also advised to wear SPF15. The improvements were dramatic. After 2 weeks, the patients saw a dramatic improvement in the size of their lesions, and after 4 weeks, nearly all lesions were resolved.
Another trial found that silymarin cream was effective in slowing the development of a skin condition that results from chemotherapy, known as hand-foot syndrome. Those in the treatment group had a silymarin cream (1%, with 80% active ingredients of silymarin flavonolignans). The cream was effective in reducing the rates of the condition in the treatment group [Elyasi 2017].
Another study found a dramatic reduction in the rate of dermatitis for patients undergoing radiation treatment. Patients with silymarin cream (Leviaderm, 0.25% silymarin) applied daily (and at least 2 hours before radiation) avoided skin complications longer, and some even avoided any dermatitis throughout radiation treatment [Becker-Schiebe 2011].
It’s important to note that other derivatives of milk thistle may also be effective. Studies demonstrate the effectiveness of silibinin independently, in terms of its anti-cancer and biological activities [Katiyar 2005] [Bhatia 1999]. Recent evidence also shows that some non-flavonolignan compounds may offer even stronger UVA protection [Vostálová 2019].
The bottom line
Milk thistle, or silymarin, is associated with several therapeutic benefits, and may be especially impactful in supporting liver health. Topical treatments are used to heal existing skin conditions (melasma) or prevent diseases and dermatitis induced by radiation.
If you’re considering using a milk thistle supplement, be aware that it has a notoriously low bioavailability. There are certain guidelines you can follow to maximize the amount of beneficial compounds your body can use. In the case of treating skin conditions, you may opt for a silymarin cream with 1-2% concentration of silymarin.
In most cases, silymarin is a long-term treatment and not a short-term fix. When supplementing, anticipate taking milk thistle for several weeks or months to realize its effects.
