What Are Herbs?

An herb, also called a botanical . . . is a plant or plant part used for its scent, flavor, and/or therapeutic properties. An herbal supplement is a type of dietary supplement that contains herbs, either alone or in mixtures.

Many people take herbal supplements to boost their immune systems, treat allergy symptoms, prevent a cold — all in an effort to be well and stay healthy. There are hundreds of herbal supplements available in the grocery store or pharmacy or for sale on the Internet. And, there are many claims about their health benefits. How can a consumer decide what’s safe or effective? This booklet will give you a basic understanding of some of the most common herbs in popular dietary supplements — their historical uses, what they’re used for now, the scientific evidence on their effectiveness, and side effects or cautions for you to consider. To manage your health, you need to be an informed consumer. Learn about herbal supplements and talk with your health care providers about everything you are doing to stay well.

Herbs as Medicine — Now and Then In the United States, nearly 1 in 5 adults — or over 38 million people — reported using a natural product, such as herbs, for health purposes in a 2007 survey. Among the top 10 natural products used were several botanicals: echinacea, flaxseed, ginseng, ginkgo, and garlic. People have used herbs as medicine since ancient times.

For example, aloe vera’s use can be traced back to early Egypt, where the plant was depicted on stone carvings. Known as the “plant of immortality,” it was presented as a burial gift to deceased pharaohs.

Lavender, native to the Mediterranean region, was used in ancient Egypt as part of the process for mummifying bodies.

Chasteberry, the fruit of the chaste tree, has long been used by women to ease menstrual problems and to stimulate the production of breast milk.

Cat’s claw, which grows wild in Central and South America, especially in the Amazon rainforest, has been used for centuries to prevent and treat disease.

Hoodia, a flowering, cactus-like plant native to the Kalahari Desert in southern Africa, has been used by the Kalahari Bushmen to reduce hunger and thirst during long hunts.

Herbs still play a part in the health practices of many countries and cultures. Ayurvedic medicine, which originated in India, uses herbs, plants, oils, common spices such as ginger and turmeric, and other naturally occurring substances. Traditional Chinese medicine uses herbs such as astragalus, bitter orange, and ginkgo for various health conditions. Herbs are also an important part of Native American healing traditions. Dandelion and goldenseal are examples of herbs used by Native Americans for different health conditions.

NCCAM’s Research on Herbs - While millions of Americans use herbal supplements, much remains to be learned about their safety and effectiveness. The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health is the Federal Government’s lead agency for studying all types of complementary and alternative medicine, including herbal supplements. This research covers a wide range of studies — from laboratory-based research studying how herbs might affect the body, to large clinical trials testing their use in people, such as studying ginkgo’s effects on memory in older adults, or whether St. John’s wort may help people with minor depression. Exploring how and why botanicals act in the body is an important step in evaluating their safety and effectiveness.

Although herbs have been used for thousands of years as natural medicines, natural does not always mean safe. Herbs can act in your body in ways similar to prescription drugs, and herbs may have side effects. They may also affect how your body responds to prescription drugs or over-the-counter medicines you take — possibly decreasing or increasing their effects.

How are herbal supplements regulated? The U.S. Food and Drug Administration (FDA) regulates herbal and other dietary supplements differently from conventional medicines. The standards of safety and effectiveness that prescription and over-the-counter medicines have to meet before they are marketed do not apply to supplements. The standards for supplements are found in the Dietary Supplement Health and Education Act (DSHEA), a Federal law that defines dietary supplements and sets product-labeling standards and health claim limits. To learn more about DSHEA, visit the FDA Web site at www.fda.gov/RegulatoryInformation/Legislation/.

Below is a list of some Herbs - you can research other herbs online to find their uses and possible benefits, or purchase a book for more information on herbs.

Aloe Vera

Aloe vera’s use can be traced back 6,000 years to early Egypt, where the plant was depicted on stone carvings. Known as the “plant of immortality,” aloe was presented as a burial gift to deceased pharaohs.

What It Is Used For - Traditionally, aloe was used topically to heal wounds and for various skin conditions, and orally as a laxative. Today, in addition to traditional uses, people take aloe orally to treat a variety of conditions, including diabetes, asthma, epilepsy, and osteoarthritis. People use aloe topically for osteoarthritis, burns, sunburns, and psoriasis. Aloe vera gel can be found in hundreds of skin products, including lotions and sunblocks. The FDA has approved aloe vera as a natural food flavoring.

How Is It Used? Aloe leaves contain a clear gel that is often used as a topical ointment. The green part of the leaf that surrounds the gel can be used to produce a juice or a dried substance (called latex) that is taken by mouth.

What the Science Says - Aloe latex contains strong laxative compounds. Products made with various components of aloe (aloin, aloe-emodin, and barbaloin) were at one time regulated by the FDA as oral over-the-counter (OTC) laxatives. In 2002, the FDA required that all OTC aloe laxative products be removed from the U.S. market or reformulated because the companies that manufactured them did not provide the necessary safety data. s Early studies show that topical aloe gel may help heal burns and abrasions. One study, however, showed that aloe gel inhibits healing of deep surgical wounds. Aloe gel has not been shown to prevent burns from radiation therapy.

There is not enough scientific evidence to support aloe vera for any of its other uses.

Side Effects and Cautions - Use of topical aloe vera is not associated with significant side effects. Abdominal cramps and diarrhea have been reported with oral use of aloe vera. Diarrhea, caused by the laxative effect of oral aloe vera, can decrease the absorption of many drugs. People with diabetes who use glucose-lowering medication should be cautious if also taking aloe by mouth because preliminary studies suggest aloe may lower blood glucose levels. There have been a few case reports of acute hepatitis from aloe vera taken orally. However, the evidence is not definitive and the safety of aloe has not been systematically studied.


Garlic is the edible bulb from a plant in the lily family. It has been used as both a medicine and a spice for thousands of years.

What It Is Used For - Garlic’s most common uses as a dietary supplement are for high cholesterol, heart disease, and high blood pressure. Garlic is also used to prevent certain types of cancer, including stomach and colon cancers.

How It Is Used - Garlic cloves can be eaten raw or cooked. They may also be dried or powdered and used in tablets and capsules. Raw garlic cloves can be used to make oils and liquid extracts.

What the Science Says - Some evidence indicates that taking garlic can slightly lower blood cholesterol levels; studies have shown positive effects for short-term (1 to 3 months) use. However, an NCCAMfunded study on the safety and effectiveness of three garlic preparations (fresh garlic, dried powdered garlic tablets, and aged garlic extract tablets) for lowering blood cholesterol levels found no effect. Preliminary research suggests that taking garlic may slow the development of atherosclerosis (hardening of the arteries), a condition that can lead to heart disease or stroke. Evidence suggests that taking garlic may slightly lower blood pressure, particularly in people with high blood pressure.

Some studies suggest consuming garlic as a regular part of the diet may lower the risk of certain cancers. However, no clinical trials have examined this. A clinical trial on the long-term use of garlic supplements to prevent stomach cancer found no effect. Recent NCCAM-funded research includes studies on how garlic interacts with certain drugs; its effects on liver function and the dilation and constriction of blood vessels; and the bioavailability (how well a substance is absorbed by the body) of allicin, the main active compound of garlic.

Side Effects and Cautions - Garlic appears to be safe for most adults. Side effects include breath and body odor, heartburn, upset stomach, and allergic reactions. These side effects are more common with raw garlic. Garlic can thin the blood (reduce the ability of blood to clot) in a manner similar to aspirin. This effect may be a problem during or after surgery. Use garlic with caution if you are planning to have surgery or dental work, or if you have a bleeding disorder. Garlic has been found to interfere with the effectiveness of saquinavir, a drug used to treat HIV infection. Its effect on other drugs has not been well studied.

Flaxseed and Flaxseed Oil

Flaxseed is the seed of the flax plant, which is believed to have originated in Egypt. It grows throughout Canada and the northwestern United States. Flaxseed oil comes from flaxseeds.

What It Is Used For - Flaxseed is most commonly used as a laxative. Flaxseed is also used for hot flashes and breast pain. Flaxseed oil is used for different conditions than flaxseed, including arthritis. Both flaxseed and flaxseed oil have been used for high cholesterol levels and in an effort to prevent cancer.

How It Is Used - Whole or crushed flaxseed can be mixed with water or juice and taken by mouth. Flaxseed is also available in powder form. Flaxseed oil is available in liquid and capsule form. Flaxseed contains lignans (phytoestrogens or plant estrogens), while flaxseed oil preparations lack lignans. What the Science Says Flaxseed contains soluble fiber, like that found in oat bran, and may have a laxative effect.

Studies of flaxseed preparations to lower cholesterol levels report mixed results. A 2009 review of the clinical research found that cholesterol-lowering effects were more apparent in postmenopausal women and in people with high initial cholesterol concentrations. Some studies suggest that alpha-linolenic acid (a substance found in flaxseed and flaxseed oil) may benefit people with heart disease. But not enough reliable data are available to determine whether flaxseed is effective for heart conditions. Study results are mixed on whether flaxseed decreases hot flashes. Although some population studies suggest that flaxseed might reduce the risk of certain cancers, there is not enough research to support a recommendation for this use.

NCCAM is funding studies on flaxseed. Recent studies are looking at its potential role in preventing or treating atherosclerosis (hardening of the arteries), breast cancer, and ovarian cysts.

Side Effects and Cautions - Flaxseed and flaxseed oil supplements seem to be well tolerated. Few side effects have been reported. Flaxseed, like any supplemental fiber source, should be taken with plenty of water; otherwise, it could worsen constipation or, in rare cases, even cause intestinal blockage. Both flaxseed and flaxseed oil can cause diarrhea. The fiber in flaxseed may lower the body’s ability to absorb medications that are taken by mouth. Flaxseed should not be taken at the same time as any conventional oral medications or other dietary supplements.


Cranberries are the fruit of a native plant of North America. These red berries are used in foods and in herbal products.

What It Is Used For - Historically, cranberry fruits and leaves were used for a variety of problems, such as wounds, urinary disorders, diarrhea, diabetes, stomach ailments, and liver problems. Recently, cranberry products have been used in the hope of preventing or treating urinary tract infections or Helicobacter pylori (H. pylori) infections that can lead to stomach ulcers, or to prevent dental plaque. Cranberry has also been reported to have antioxidant and anticancer activity.

How It Is Used - The berries are used to produce beverages and many other food products, as well as dietary supplements in the form of extracts, capsules, or tablets.

What the Science Says - There is some evidence that cranberry can help to prevent urinary tract infections; however, the evidence is not definitive, and more research is needed. Cranberry has not been shown to be effective as a treatment for an existing urinary tract infection. Research shows that components found in cranberry may prevent bacteria, such as E. coli, from clinging to the cells along the walls of the urinary tract and causing infection. There is also preliminary evidence that cranberry may reduce the ability of H. pylori bacteria to live in the stomach and cause ulcers. Findings from a few laboratory studies suggest that cranberry may have antioxidant properties and may also be able to reduce dental plaque (a cause of gum disease).

NCCAM is funding studies of cranberry, primarily to better understand its effects on urinary tract infection. The Office of Dietary Supplements and other NIH agencies are also supporting cranberry research; for example, the National Institute on Aging is funding a laboratory study of potential anti-aging effects.

Side Effects and Cautions - Drinking cranberry juice products appears to be safe, although excessive amounts could cause gastrointestinal upset or diarrhea. People who think they have a urinary tract infection should see a health care provider for proper diagnosis and treatment. Cranberry products should not be used to treat infection. There are some indications that cranberry should be used cautiously by people who take blood-thinning drugs (such as warfarin), medications that affect the liver, or aspirin.


Dandelion greens are edible and are a rich source of vitamin A. Dandelion has been used in many traditional medical systems, including Native American and traditional Arabic medicine.

What It Is Used For - Historically, dandelion was most commonly used to treat liver diseases, kidney diseases, and spleen problems. Less commonly, dandelion was used to treat digestive problems and skin conditions. Today, dandelion is used by some as a liver or kidney “tonic,” as a diuretic, and for minor digestive problems.

How It Is Used - The leaves and roots of the dandelion, or the whole plant, are used fresh or dried in teas, capsules, or extracts. Dandelion leaves are used in salads or as a cooked green, and the flowers are used to make wine.

What the Science Says - There is no compelling scientific evidence for using dandelion as a treatment for any medical condition.

Side Effects and Cautions - Dandelion use is generally considered safe. However, there have been rare reports of upset stomach and diarrhea, and some people are allergic to the plant. People with an inflamed or infected gallbladder, or blocked bile ducts, should avoid using dandelion.

Green Tea

All types of tea (green, black, and oolong) are produced from the Camellia sinensis plant using different methods. Fresh leaves from the Camellia sinensis plant are steamed to produce green tea.

What It Is Used For - Green tea and green tea extracts, such as its component EGCG, have been used to prevent and treat a variety of cancers, including breast, stomach, and skin cancers. Green tea and green tea extracts have also been used for improving mental alertness, aiding in weight loss, lowering cholesterol levels, and protecting skin from sun damage.

How It Is Used - Green tea is usually brewed and drunk as a beverage. Green tea extracts can be taken in capsules and are sometimes used in skin products.

What the Science Says - Laboratory studies suggest that green tea may help protect against or slow the growth of certain cancers, but studies in people have shown mixed results. Some evidence suggests that the use of green tea preparations improves mental alertness, most likely because of its caffeine content. There are not enough reliable data to determine whether green tea can aid in weight loss, lower blood cholesterol levels, or protect the skin from sun damage. NCCAM supports studies to learn more about the components in green tea and their effects on conditions such as cancer, diabetes, and heart disease.

Side Effects and Cautions - Green tea is safe for most adults when used in moderate amounts. There have been some case reports of liver problems in people taking concentrated green tea extracts. This problem does not seem to be connected with green tea infusions or beverages. Although these cases are very rare and the evidence is not definitive, experts suggest that concentrated green tea extracts be taken with food and that people should discontinue use and consult a heath care practitioner if they have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice. Green tea and green tea extracts contain caffeine. Caffeine can cause insomnia, anxiety, irritability, upset stomach, nausea, diarrhea, or frequent urination in some people. Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.