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Topics in Complementary and Alternative Therapies (PDQ®)

Patient Version

Botanicals/Herbal Products

Black Cohosh

Black cohosh is a North American perennial herb. A substance found in the root of this plant has been used in some cultures to treat a number of medical conditions. Black cohosh has been studied to relieve hot flashes. However, randomized, placebo-controlled clinical trials using this herb have found that black cohosh is no better than a placebo in relieving hot flashes.

Cannabis and Cannabinoids

Cannabis, also known as marijuana, is a plant from Central Asia that is grown in many parts of the world today. In the United States, it is a controlled substance and is classified as a Schedule I agent (a drug with increased potential for abuse and no known medical use). The Cannabis plant makes a resin that contains active chemicals called cannabinoids. Cannabinoids cause drug-like effects throughout the body, including the central nervous system and the immune system. Possible benefits of medicinal Cannabis for people living with cancer include control of nausea and vomiting, increasing appetite, relieving pain, and improving sleep.

Essiac/Flor Essence

Essiac and Flor Essence are herbal tea mixtures originally developed in Canada. They are marketed worldwide as dietary supplements. Supporters of Essiac and Flor Essence say that these products can help detoxify the body, make the immune system stronger, and fight cancer. There is no evidence in clinical trials that Essiac or Flor Essence can be effective in treating patients with cancer.


Flaxseed comes from the flax plant. It is a rich source of omega-3 fatty acid, fiber, and a compound called lignin. It is being studied in the prevention of several types of cancer. Flaxseed has also been studied for its effect on hot flashes.


Ginger is an herb that is used in cooking and in some cultures to treat medical conditions such as nausea. It can be used fresh, dried and powdered, or as a juice or oil. Ginger has been studied for the relief of nausea and vomiting in cancer patients.

  • See the Ginger section in the PDQ health professional summary on Nausea and Vomiting for information about randomized control trials of ginger in cancer patients.


Ginseng is an herb that is used to treat fatigue. It may be taken in capsules of ground ginseng root. Studies of ginseng have been done in patients either during or after their treatment for cancer. Patients who were given ginseng had less fatigue than patients who were given a placebo (inactive substance).

  • See the Intervention section in the PDQ health professional summary on Fatigue for more information.


L-carnitine is a dietary supplement that is thought to be helpful in treating fatigue related to cancer. L-carnitine helps the body make energy and lowers inflammation that may be linked to fatigue.

Milk Thistle

Milk thistle is a plant whose fruit and seeds have been used for more than 2,000 years as a treatment for liver and bile duct disorders. The active substance in milk thistle is silymarin. Laboratory studies show that silymarin stimulates repair of liver tissue and acts as an antioxidant that protects against cell damage. It slows the growth of certain types of cancer cells and may make some types of chemotherapy less toxic and more effective.

  • See the PDQ patient summary on Milk Thistle for more information.

Mistletoe Extracts

Mistletoe is a semiparasitic plant that has been used since ancient times to treat many ailments. It is used commonly in Europe, where a variety of different extracts are made and marketed as injectable prescription drugs. The FDA does not allow these injectable drugs to be sold in the United States and they are not approved as a treatment for patients with cancer.


PC-SPES is a patented mixture of eight herbs. Each herb used in PC-SPES has been reported to have anti-inflammatory, antioxidant, or anticancer properties. PC-SPES was taken off the market because some batches were found to contain prescription medicines in addition to the herbs. The manufacturer is no longer in business and PC-SPES is no longer being made.

  • See the PDQ patient summary on PC-SPES for more information.

St. John's Wort

St. John’s wort is a plant with yellow flowers that has been used since ancient times for medical conditions. St. John's wort is sold as an over-the-counter herbal treatment for depression. Studies comparing St. John's wort with standard antidepressant medicines have shown mixed results. St. John's wort may change the way other medicines work, including anticancer medicines.

  • See the Treatment of Depression section in the PDQ patient summary on Depression for information about clinical trials that have studied St. John’s wort as a treatment for depression.

Selected Vegetables/Sun's Soup

“Selected Vegetables” and “Sun’s Soup” are different mixtures of vegetables and herbs that have been studied as treatments for cancer. Dried and frozen forms of Selected Vegetables are sold in the United States as dietary supplements. The vegetables and herbs in Selected Vegetables/Sun’s Soup are thought to have substances that block the growth of cancer cells and/or help the body's immune system kill cancer cells. There is limited evidence that Selected Vegetables/Sun’s Soup is useful as a treatment for cancer and no randomized or controlled clinical trials have been done.

  • Updated: April 2, 2015