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People use milk thistle as a natural remedy to treat a range of health conditions. But are there any proven health benefits of it?

Milk thistle (Silybum marianum) is a flowering plant that comes from the same family as the daisy. Also known as Mary thistle or holy thistle, milk thistle grows in Mediterranean countries and people use it to make natural remedies.

The active ingredient in milk thistle is called silymarin. Doctors mainly use the plant to treat liver problems, but some people claim it can lower cholesterol and help manage type 2 diabetes.

This article explores potential milk thistle benefits and examines whether there is any scientific evidence to support its use. It also looks at how to use milk thistle and whether there are any risks to consider.

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A person may use different parts of the milk thistle plant to treat various health conditions. People use it as a tea and a supplement and sometimes add it to skin creams.

The most common use of milk thistle is for liver problems. Some people claim it can help to treat:

Other potential benefits include protecting heart health by lowering cholesterol levels and helping people manage type 2 diabetes.

We explore the potential health benefits of milk thistle below.

Supports liver health

A 2016 study found that milk thistle improved diet-induced liver damage in mice. The medical community needs more evidence to prove that milk thistle benefits human livers in the same way.

However, researchers theorize that it does. The active ingredient in milk thistle, silymarin, acts as an antioxidant by reducing free radical production. Scientists think this creates a detoxifying effect, which is why milk thistle may be beneficial for liver problems.

Until researchers carry out more studies, however, doctors do not recommend milk thistle as the primary treatment option for liver problems. But it may be a helpful complementary treatment to try if a healthcare professional approves it.

Promotes skin health

woman applying essential oil to skin on leg to moisturize.Share on Pinterest
People may use milk thistle oil topically to improve skin health.

Milk thistle may help to promote healthy skin. A 2015 study found that it helped to improve inflammatory skin conditions when applied to the skin of mice.

Researchers also found in another study that milk thistle had antioxidant and anti-aging effects on human skin cells in a laboratory environment. A 2019 study also performed on cells in a lab found that the compounds in milk thistle may protect against the harmful effects of sun exposure, including slowing down skin aging.

Researchers must carry out further studies on humans to identify what benefits a person can expect from applying milk thistle to their skin.

Reduces cholesterol

High cholesterol can lead to problems with heart health and increase a person’s chance of stroke. Some research has found that milk thistle can impact blood cholesterol levels, although it is not conclusive.

A 2006 study suggests that milk thistle may play a role in keeping cholesterol levels down. It found that cholesterol levels were lower in people taking milk thistle to treat diabetes than those taking a placebo.

In a 2016 study, researchers fed rats a high-cholesterol diet. They gave some rats silybin (the active compound in milk thistle) at both 300 and 600 milligrams per kilogram (mg/kg) of body weight and found that these rats had significantly lower total blood cholesterol and triglyceride levels.

Supports weight loss

Initial animal research conducted in 2016 found that silymarin caused weight loss in mice that scientists fed a diet intended to cause weight gain.

This suggests milk thistle may be beneficial for those looking to lose weight. Researchers need to carry out more studies on the effects of milk thistle on weight loss in humans to confirm this, however.

Reduces insulin resistance

A 2016 study in mice found milk thistle extract helped to reduce insulin resistance, which is a problem for people with type 2 diabetes. Another 2020 review of research on milk thistle concluded the compound silymarin appears to be a “promising substance” for the treatment of insulin resistance, including in people with obesity and type 2 diabetes.

Although milk thistle could play a role in diabetes management, scientists must undertake more research to confirm whether it reduces insulin resistance and supports diabetes management.

Improves allergic asthma symptoms

Asthma is a chronic inflammatory disease where the immune system overreacts to environmental triggers, leading to inflammation in the airways. The active ingredient in milk thistle may help to reduce inflammation.

A 2012 study found that silymarin helped to protect against inflammation in the airways of mice with allergic asthma. Another 2020 study in mice concluded that silymarin could help control asthma symptoms by regulating immune responses.

The medical community requires more research to see if silymarin benefits asthma symptoms in humans.

Limits the spread of cancer

Milk thistle may help to stop the spread of certain types of cancer.

Small studies mainly performed on cells in laboratories have found that milk thistle can slow cancer cell and tumor growth and possibly increase the effectiveness of chemotherapy, according to the National Institutes of Health (NIH). Researchers have found benefits for several types of cancer, including:

  • prostate cancer
  • breast cancer
  • cervical cancer
  • leukemia
  • skin cancer
  • colorectal cancer

Several small studies have also found that milk thistle may decrease the side effects of cancer treatments, including radiation, surgery, and chemotherapy.

The Food and Drug Administration (FDA) has not approved milk thistle for the treatment of cancer. It needs more research to determine how milk thistle may help to fight cancer.

Supports bone health

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Milk thistle tea may help to prevent bone loss caused by a lack of estrogen.

Milk thistle could play an essential role in supporting bone health. A 2013 study found that milk thistle helped to prevent bone loss.

The study looked specifically at bone loss caused by a deficiency in estrogen among rats that had their ovaries removed. It is not yet clear whether milk thistle is equally beneficial for bone loss with a different cause.

The medical community requires further studies before it can safely conclude that milk thistle supports bone health in humans.

Improves cognition

A 2015 study in worms found that milk thistle increased resistance to oxidative stress. Oxidative stress is a potential cause of Alzheimer’s disease.

In this way, milk thistle may help improve cognition and treat degenerative conditions that affect the mind. Researchers must carry out more studies on humans to confirm the effects of milk thistle on cognition.

Supports the immune system

Milk thistle may help strengthen a person’s immune response. It could help the body fight off infection as well as reduce chronic inflammation produced by the immune system.

Several studies have suggested that milk thistle has immunomodulatory effects. Researchers found silymarin stimulated the immune system. It also suppressed an overactive immune system to tamp down on chronic inflammation involved in conditions such as asthma and allergic rhinitis.

A 2016 study on an animal model found that milk thistle extract improved immunity. An older study found that milk thistle extract had a positive effect on immune response in humans.

More studies with human participants could allow scientists to say with certainty that milk thistle supports a person’s immune system.

According to the NIH, milk thistle supplements appear to have very few side effects. Rarely, taking milk thistle may cause:

  • a laxative effect
  • nausea
  • heartburn
  • upset stomach
  • a mild allergic reaction, at high doses

There is not much information about the interaction of milk thistle with other drugs, including anticancer medications and radiation therapy. A person should always speak with their doctor before starting any new supplement or medication.

Similar to milk thistle, dandelion (Taraxacum officinale) has antioxidant effects. It reportedly has other potential health benefits, which may include:

  • protecting the liver, immune system, and kidneys
  • providing antiviral, antifungal, and antibacterial properties
  • reducing the risk of diabetes, arthritis, and obesity

Due to some similar potential health benefits, producers have studied milk thistle and dandelion supplements and sold them together.

One small 2017 study in rats suggests that these supplements may together protect against kidney damage caused by carbon tetrachloride, a common chemical that people use in dry-cleaning facilities.

Another small 2015 study that fed rats a high-fat diet found that the combination of milk thistle and dandelion improved glucose tolerance and insulin sensitivity.

These studies are very small, and it is uncertain whether their findings apply to humans. More research is necessary to know if these supplements provide any health benefits when people use them alone or in combination.

Milk thistle seeds contain silymarin. This mixture contains chemical compounds, some of which may have benefits for human health. These include:

  • silybin
  • isosilybin
  • silychristin
  • isosilychristin
  • silydianin
  • taxifolin

Most research has looked at the benefits of silymarin and silybin.

Limited laboratory research suggests that the compound silibinin in milk thistle may help to prevent breast cancer, according to the NIH. Researchers think it may also slow down the growth of cancer cells.

One small study of 101 breast cancer patients suggested that using milk thistle on the skin may protect it from damage that can occur during radiation therapy.

However, the extracts in milk thistle could act like estrogen. It may not be safe for people with hormone-sensitive breast cancer.

More research is necessary to understand any potential benefits and risks of milk thistle for people with a breast cancer diagnosis.

Milk thistle is available as a supplement from many health food stores. There is no standard dose of milk thistle, so it is best to read the dosage suggested on the packaging.

Milk thistle is also available as a tea. If drinking milk thistle tea, it is best to limit intake to 6 cups a day.

Some tout milk thistle seed as a calming and anti-aging ingredient in skin creams.

The FDA has not approved milk thistle to treat any health conditions.

Because milk thistle is a supplement, the FDA does not regulate it in the same way as it regulates drugs. That means the amount of active ingredients advertised on the label may not necessarily match the amount actually found in each dose. For this reason, it is important to buy milk thistle from reputable retailers.

As with any natural remedy, people should discuss using milk thistle with a doctor before taking it.

Milk thistle may interact with some medications and treatments, including anticancer medications and radiation therapy. It could also have similar effects on the body to estrogen. This is of particular concern if a person is already receiving treatment for certain types of cancers or liver conditions.

Milk thistle has a range of potential health benefits due to its active ingredient, silymarin, which is an antioxidant.

Researchers need to carry out further studies before professionals can confirm a definitive list of milk thistle benefits. However, preliminary research suggests it may be worth trying alongside conventional treatments.

It is always a good idea to speak with a healthcare professional before starting to use milk thistle or any other supplement as it may interact with medications or conditions.

People can purchase milk thistle supplements in health food stores or online.