Written by Helen West, RD (UK) on January 19, 2018
Milk thistle is an herbal remedy derived from the milk thistle plant, also known as Silybum marianum.
This prickly plant has distinctive purple flowers and white veins, which traditional stories say were caused by a drop of the Virgin Mary's milk falling onto its leaves.
The active ingredients in milk thistle are a group of plant compounds collectively known as silymarin (1).
Its herbal remedy is known as milk thistle extract. Milk thistle extract has a high amount of silymarin (between 65–80%) that has been concentrated from the milk thistle plant.
The silymarin extracted from milk thistle is known to have antioxidant, antiviral and anti-inflammatory properties (2, 3, 4).
In fact, it has traditionally been used to treat liver and gallbladder disorders, promote breast milk production, prevent and treat cancer and even protect the liver from snake bites, alcohol and other environmental poisons.
Here are 7 science-based benefits of milk thistle.
1. Milk Thistle Protects Your Liver
Milk thistle is often promoted for its liver-protecting effects.
It’s regularly used as a complementary therapy by people who have liver damage due to conditions like alcoholic liver disease, non-alcoholic fatty liver disease, hepatitis and even liver cancer (1, 5, 6).
It’s also used to protect the liver against toxins like amatoxin, which is produced by the death cap mushroom and is deadly if ingested (7, 8).
Studies have shown improvements in liver function in people with liver diseases who have taken a milk thistle supplement, suggesting it could help reduce liver inflammation and liver damage (9).
Although more research is needed on how it works, milk thistle is thought to reduce damage to the liver caused by free radicals, which are produced when your liver metabolizes toxic substances.
One study also found that it may slightly extend the life expectancy of people with cirrhosis of the liver due to alcoholic liver disease (10).
However, the results from studies have been mixed, and not all have found milk thistle extract to have a beneficial effect on liver disease.
Thus, more studies are needed to determine what dose and length of treatment are needed for specific liver conditions (2, 11, 12).
And although milk thistle extract is commonly used as a complementary therapy for people with liver diseases, there’s currently no evidence that it can prevent you from getting these conditions, especially if you have an unhealthy lifestyle.
2. It May Help Prevent Age-Related Decline in Brain Function
Milk thistle has been used as a traditional remedy for neurological conditions like Alzheimer's and Parkinson’s disease for over two thousand years (13).
Its anti-inflammatory and antioxidant properties mean that it is possibly neuroprotective and could help prevent the decline in brain function you experience as you age (14, 15).
In test-tube and animal studies, silymarin has been shown to prevent oxidative damage to brain cells, which could help prevent mental decline (16, 17).
These studies have also seen that milk thistle may be able to reduce the number of amyloid plaques in the brains of animals with Alzheimer's disease (18, 19, 20).
Amyloid plaques are sticky clusters of amyloid proteins that can build up between nerve cells as you age.
They are seen in very high numbers in the brains of people with Alzheimer's disease, meaning that milk thistle could potentially be used to help treat this difficult condition (21).
However, there are currently no human studies examining the effects of milk thistle in people with Alzheimer's or other neurological conditions like dementia and Parkinson's.
Moreover, it’s unclear whether milk thistle is well enough absorbed in people to allow adequate amounts to pass through the blood-brain barrier. It’s also unknown what doses would need to be prescribed for it to have a beneficial effect (18).
