What Is Mistletoe?

Mistletoe (Viscum album) is a type of parasitic plant. It grows on various types of trees, such as apple, oak, and pine. Viscum album, in particular, is also called European mistletoe and differs from American mistletoe, which is commonly used as a decoration.

Mistletoe has been harvested for its leaves, stems, and berries for centuries due to its perceived medicinal properties. Mistletoe extract is most commonly prescribed as a complementary treatment for cancer in Europe. Evidence for its use in cancer and other health concerns is mostly lacking.

The Food and Drug Administration (FDA) has not approved it for use in cancer or any other health condition. However, it is available in products as a dietary supplement.

This article will look at the science behind the potential uses of mistletoe. It will also cover other important information, including side effects, drug interactions, dosage, and precautions for mistletoe's use as a supplement.

Uses of Mistletoe

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian (RD), pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease. 

Mistletoe use has been studied for appropriateness in several health conditions but many studies have been performed in labs, on animal models, or are of poor quality.

What follows is a look at some evidence surrounding the common uses of mistletoe.

Neurological Disorders

Mistletoe is thought to have properties that make it helpful in the treatment of various neurological disorders.

Researchers have found that chemical components in mistletoe may promote the release of the neurotransmitters dopamine, glutamic acid, and GABA (gamma-aminobutyric acid). The release of these neurotransmitters may help improve conditions like insomnia and epilepsy.

The lectins in mistletoe are thought to be responsible for the potential benefits of the herb on neurological disorders.

At this time, though, research surrounding mistletoe and neurological disorders has been chiefly performed in lab settings or on animal models. More robust human trials are needed to confirm mistletoe's role in treating epilepsy, insomnia, and other neurological disorders.

Cancer Care

According to the National Cancer Institute, mistletoe is one of the most widely researched alternative therapies for people living with cancer. Research suggests that mistletoe may stimulate the immune system to help fight cancer.

Mistletoe may help people with cancer in more than one way.

Mistletoe extracts may possess anticancer qualities, as the herb has been found to inhibit cancer cell proliferation (spread) and even kill existing cancer cells in experimental laboratory settings. 

Research also suggests that mistletoe may effectively improve the quality of life of people with cancer. According to one review, mistletoe has been found to improve common side effects of cancer treatment, including pain and fatigue. However, some of the studies used in the review were of poor quality.

In other reviews, mistletoe has most commonly been reported to improve other indicators of quality of life, including sleep, nausea, appetite, anxiety, and emotional and functional well-being.

Cardiovascular Health

Some research suggests that mistletoe may benefit cardiovascular (heart) health.

One study performed on rats found that mistletoe may help prevent high blood pressure, thus reducing the risk of issues like coronary heart disease and stroke.

Other research has shown that mistletoe may have antioxidant properties. Antioxidants are thought to improve circulation and protect the heart and blood vessels from damage.

Once again, though, human trials are lacking in this area, and more research is needed to confirm mistletoe's potential role in heart health.

Diabetes

Mistletoe has been used for generations to help balance blood sugar levels. However, research in this area has mostly been performed in labs or on animal models, and results are conflicting.

Some research has found that mistletoe may be anti-glycemic, meaning it may help reduce excess glucose (sugar) in the blood. Mistletoe is also thought to stimulate the secretion of insulin, the hormone needed to remove glucose from the bloodstream.

One animal study suggests that mistletoe extract may protect liver cells from free radical damage, a possible side effect of diabetes.

Further research, including human trials, is needed to understand mistletoe’s potential role in balancing glucose levels.

What Are the Side Effects of Mistletoe?

When used in the recommended amounts, mistletoe is rarely associated with side effects. However, side effects are possible when using mistletoe and may be mild or severe.

Common Side Effects

Although side effects are more likely to occur when mistletoe is used in doses that are too high, anyone may experience side effects.

More common side effects of mistletoe include:

• Nausea
• Vomiting
• Upset stomach
• Chills
• Fever
• Pruritus (itchy skin)
• Headache
• Fatigue

Injectable forms of mistletoe (mostly used in Europe) may cause soreness, pain, and inflammation at the injection site, as well as fever and chills.

Severe Side Effects

Mistletoe rarely causes severe side effects.

However, there have been a few reported cases of severe allergic reactions to mistletoe. Anaphylaxis was also reported in some of these cases. If you experience anaphylaxis, a potentially life-threatening reaction, you must seek immediate medical attention.

Rare cases of liver damage and toxicity have also been reported. However, the people who experienced liver damage were also taking other herbs, making it impossible to pinpoint mistletoe as the sole cause.

Precautions

There is still much to learn about mistletoe. Because of this, certain people should take extra precautions before using the herb.

Mistletoe is thought to be unsafe during pregnancy. Therefore, you should avoid mistletoe if you are pregnant.

It is unknown if mistletoe is safe to use while breastfeeding. To be safe, avoid using mistletoe while nursing.

More research is needed to determine the overall safety of mistletoe. Please speak with a healthcare provider before using mistletoe, especially if you have any health conditions.

Dosage: How Much Mistletoe Should I Take?

There are no dosage recommendations for mistletoe. This is due to an overall lack of information regarding the safety and effectiveness of the herb.

Follow all dosing guidelines as listed on the label of any commercially available mistletoe product. Your healthcare provider may also be able to help you find the right mistletoe dose for your specific needs.

What Happens If I Take Too Much Mistletoe?

Although mistletoe overdose has not been reported, the herb may be toxic if taken in high doses.

Injectable mistletoe is not considered toxic, but oral forms may cause side effects or severe reactions if used improperly.

Although rare, some cases of anaphylaxis, allergic reaction, and liver toxicity have been reported in people who have taken more mistletoe than they should.

It's also worth noting again that American mistletoe should never be ingested, as its leaves and berries are considered toxic. This type of mistletoe is mostly used for decoration.

You can avoid mistletoe toxicity by taking the herb exactly as directed.

Interactions

Mistletoe may interact with various medications, as well as other herbs. However, possible interactions are not well-documented, which means there is not much information available on this subject.

Lab studies on mistletoe indicated no major interactions between the herb and various drugs metabolized by the liver. Another study done in a lab found that mistletoe didn't negatively interact with various cancer therapies.

An interaction between mistletoe and antihypertensive medications is not well-supported by scientific evidence. No interactions between mistletoe and medications, herbs, or foods have been properly reviewed in humans.

It is essential that you read the ingredients list and nutrition facts panel of any new supplement before purchasing. Doing so will help you know which ingredients are in it and how much of each ingredient is included in the supplement. It is best to review supplement labels with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications. 

How to Store Mistletoe

It's important to store supplements properly to ensure proper shelf life.

Mistletoe should be stored in a cool, dry place that is kept from direct sunlight. Mistletoe extracts don't typically require refrigeration, but check the product label for storage instructions. Discard mistletoe once the expiration date has passed.

Be sure to keep all supplements out of reach of pets and small children.

Similar Supplements

With so many supplements on the market, it can be challenging to choose the right one. That's why working with your healthcare provider regarding supplements is always best.

Some supplements and herbs that have been studied for similar uses include:

• Ginger: While no supplements or herbs can prevent cancer, some, like ginger and mistletoe, may help with the side effects of chemotherapy, like nausea and vomiting. A recent systematic review found that daily ginger supplementation may reduce vomiting caused by chemotherapy. However, results have been mixed regarding its ability to reduce nausea.
• L-arginine: An amino acid naturally produced by your body, L-arginine may help lower blood pressure. Although research has yielded some mixed results, L-arginine is thought to modestly reduce blood pressure, with a greater decrease seen in people with high blood pressure (hypertension).
• Cinnamon: Cinnamon may do more than add flavor to baked goods and oatmeal. Some research shows that cinnamon may be useful in the treatment of type 2 diabetes, as it is thought to help reduce blood sugar levels. However, more research is needed in this area, and cinnamon shouldn't replace conventional treatments for diabetes.

Sources of Mistletoe & What to Look For

Mistletoe is not naturally found in foods but comes in several supplement forms. It's important to know what to look for when choosing new supplements.

Food Sources of Mistletoe

Mistletoe in its raw form is not edible. Eating mistletoe leaves and berries may cause an upset stomach and other side effects.

Some people use dried mistletoe to make tea. Mistletoe is also sold in individual tea bags.

Mistletoe Supplements

Mistletoe is available at health foods stores and online as a liquid extract, dried herb, or loose-leaf tea. Some oral supplements, like capsules and tablets, may contain mistletoe in combination with other herbs and nutrients.

It's important that you avoid using American mistletoe and only use European mistletoe (Viscum album) or other safe herb varieties.

It's also worth noting that much of the scientific research has focused on injected forms of mistletoe that are not approved as prescription medications in the United States. These are mostly used in Europe.

If using an oral mistletoe supplement, be sure to follow the dosing instructions carefully to avoid unwanted side effects.

Recall that supplements are not regulated like prescription drugs or conventional food products in the United States. Since the FDA and other government agencies do not approve supplements, it's best to look for brands tested by third-party agencies. These include ConsumerLab, USP, and NSF.

Summary 

Mistletoe may be more than just a symbolic token of the holiday season. Although there are many species of the plant, European mistletoe has been used for centuries for its potential health benefits.

Scientific evidence surrounding mistletoe's uses is lacking, with many studies being performed in labs or on animal models. More human trials are needed on mistletoe.

Discuss any herbs and supplements you plan to use with your healthcare provider.