How do herbal products cause weight loss?

Most herbal weight loss products work by:

  • Increasing urination and/or bowel movements
  • Stimulating the central nervous system (speeds up the body's mental and physical activity; caffeine is a central nervous system stimulant)
  • Increasing serotonin levels, a chemical in the brain that creates a "feeling of fullness"

However, herbal preparations will not produce permanent weight loss. Also, herbal weight-loss products contain many ingredients, some of which have serious side effects and can lead to dangerous health situations (toxicities). Most people who sell herbal products have limited knowledge how these products work and wouldn't be able to tell you about reported problems with the herbs or how they might affect the drugs you may be taking. Many herbal manufacturers also make "false claims" about the health benefits of these products. For all of these reasons and lack of proven health benefits, use of herbal products as weight-loss aids is not encouraged.

Despite some risks and lack of proven health benefits, if I am still interested in taking herbal products, what should I know?

If ill, see a doctor or talk with a health care professional.

  • Do not take herbs if you pregnant or trying to become pregnant.
  • Do not take herbs if you are nursing.
  • Do not give herbs to a baby or child.
  • Do not take large amounts of any one herbal product.
  • Do not take any herb on a daily basis.
  • Only buy preparations that have the plants ingredients listed on the package. (Note: There is no guarantee of the health benefits promoted by herbal products.)
  • Do not take herbal remedies if you are taking a long-term drug (eg, high blood pressure medications, antidepressants, and other drugs). If you are unsure, talk with a health care provider before taking any herbal preparation.
  • Do not take herbal remedies if you are taking drugs that have a narrow margin for safety, such as warfarin (Coumadin®), digoxin, phenytoin (Dilantin®), lithium (Lithobid®, Eskalith®), theophylline (Theo-Dur®, Theo-24®, others), etc. If you are unsure, talk with a health care provider before taking any herbal preparation.
  • Always tell your health care provider if you are taking any herbal remedy or alternative medicine.

What are some of these over-the-counter and herbal products and what should I know about each of them?

There are many over-the-counter and herbal products. Not all can be discussed here. Here are some key points of some of the most popular products and what ‘science' says today about their effectiveness as weight loss agents.

Over-the-counter appetite suppressants: Appetite suppressants are drugs that may help you lose weight by "tricking" your body into making you feel full and no longer hungry.

Appetite suppressants can work, but they only work while you are taking them. However, long-term use can lead to addiction and create health complications. To lose weight, you must also adjust your eating habits; otherwise you will simply regain any lost weight.

One appetite suppressant product, phenylpropanolamine (PPA), is no longer being sold in the US. It was pulled off the market because it was associated with an increased risk of strokes.

Ephedrine: Ephedrine is a common ingredient in herbal dietary supplements used for weight loss. Ephedrine is also an ingredient in asthma medicine. In addition, it is used to make methamphetamine, more commonly called speed. In fact, there's only a slight chemical difference between methamphetamine and ephedrine.

Ephedrine can slightly decrease your appetite, but no studies have shown it to be effective in weight loss. Ephedrine can be dangerous. It can cause high blood pressure, changes in heart rate, trouble sleeping (insomnia), nervousness, tremors, seizures, heart attacks, strokes, and even death. Ephedrine can also interact with many prescription and over-the-counter medications. In the US, ephedra-containing dietary supplements are no longer available.

St. John's wort: St. John's wort is an herbal – also called hypericum – that has been used for centuries to treat mental disorders, nerve pain, malaria, insect bites, wounds, burns, and other conditions. More recently, St. John's wort has been studied to treat depression. Two large studies have shown it to be no more effective than placebo.

Not many studies have looked at the use of St. John's wort as a weight-loss agent. If you are taking St. John's wort, you should avoid eating tyramine-containing foods (i.e., aged meats, cheese, wines, etc). Also, do not take St. John's wort if you are taking any of the following drugs: fluoxetine (Prozac®), sertraline (Zoloft®), paroxetine (Paxil®), venlafaxine (Effexor®), trazodone (Desyrel®), mirtazapine (Remeron®), nefazodone (Serzone®), meperidine (Demerol®), buspirone (Buspar®), and dextromethorphan (contained in various over-the-counter cold remedies). The use of St. John's wort for weight loss is potentially very dangerous and it should not be used as a weight-loss product.

5-hydroxytryptophan (5-HTP). 5-hydroxytryptophan (5-HTP) is found in some over-the-counter weight loss formulas. This extract from a West African plant seed contains an ingredient that is linked to a rare and potentially deadly blood disorder. It has not been proven to be an effective weight-loss agent. Until more is known, 5-HTP products should be avoided.

Chitosan: This dietary supplement is made from chitin, a starch found in the skeleton of shrimp, crab, and other shellfish. There is a concern that people with allergies to shellfish might also be allergic to chitosan. Chitosan works by binding with fat in fatty foods, moving it through the digestive tract, and then passing it out of the body in bowel movements without the fat being able to be absorbed. Some research suggests that combining chitosan with a calorie-restricted diet might result in a small amount of weight loss. But taking chitosan without cutting calories doesn't seem to cause weight loss.

Pyruvate: Pyruvate is formed in the body during the digestion of carbohydrates and proteins. According to some studies, it may have a slight effect in helping you shed pounds. Found in the form of pyruvic acid, pyruvate is in many different types of foods, including red apples, cheese, and red wine. Pyruvate appears to be safe, but its claims of boosting metabolism, decreasing appetite, and aiding in weight loss need further study.

Aloe: Aloe (often called aloe vera) is a plant related to cactus. Oral forms of aloe are added to herbal weight-loss products. Oral aloe causes bowel movements and many aloe weight-loss products are marketed as "internal cleansers." The use of aloe supplements has not been shown to be effective for permanent weight loss. Taking oral aloe can lead to side effects such as abdominal cramping, diarrhea, electrolyte disturbances, and decreases in potassium. Therefore, taking oral aloe is likely unsafe, especially at high doses.

Cascara: Cascara is only marketed as a dietary supplement. It is a common ingredient in weight loss products and is mostly used as a laxative for constipation. Misuse of this herb has caused disturbances in electrolytes (such as potassium and sodium). Electrolytes help your body maintain normal functioning. Do not take if you are pregnant or lactating (can be passed into breast milk). Cascara may interact with medications such as digoxin and diuretics.

Dandelion: Dandelion is a natural diuretic (a substance that makes you urinate more often). This is how it causes weight loss. Dandelion has been known to cause allergic reactions. People who are allergic to ragweed and related plants (daisies, chrysanthemums, marigolds) are likely to be allergic to dandelion.

Glucomannan: Glucomannan is a sugar made from the root of the konjac plant (Amorphophallus konjac). It is available in powder, capsules, and tablet forms. Glucomannan might work in the stomach and intestines by absorbing water to form a bulky fiber that treats constipation. It may also slow the absorption of sugar and cholesterol from the gut. Glucomannan tablets are not considered safe as they can sometimes cause blockages of the throat or intestines. Glucomannan may interfere with blood sugar control. Blood sugar should be closely monitored if you have diabetes and use glucomannan.

Guarana: Made from the seeds of a plant native to Brazil, guarana is an effective central nervous system stimulant. It is used as a weight loss product due to its stimulant and diuretic effects. Guarana contains caffeine and may cause high blood pressure. Some of the extracts have been known to interact with anticoagulants (i.e., warfarin [Coumadin®]) and lengthen bleeding time if there was a health emergency. Many advertisements state that guarana is free from side effects; however, this statement is not true. Side effects from guarana may include nausea, dizziness, and anxiety. People who take guarana on a regular basis and suddenly reduce the amount they've been taking may experience caffeine withdrawal symptoms.

Yerba mate: Also known as Paraguay tea, yerba mate is a strong central nervous system stimulant (the doses typically used mimic that of 100 to 200 milligrams of caffeine). The main reported side effects excessive central nervous system stimulation (speeding up the body's mental and physical activity) and high blood pressure. Yerba mate has not been proven as a weight-loss aid. A few cases of poisoning (leading to hospitalization) have been reported with use of this product. When taken in large amounts or for long periods of time, yerba mate increases the risk of mouth, esophageal, laryngeal, kidney, bladder, and lung cancers. This risk is especially high for people who smoke or drink alcohol.

Guar gum: Also known as guar, guar flour, and jaguar gum, guar gum is a dietary fiber obtained from the Indian cluster bean. Guar gum is often used as a thickening agent for foods and drugs. It has been studied for decreasing cholesterol, managing diabetes, and for weight loss. As a weight-loss product, it helps move foods through the digestive tract and firms up stool. It can decrease appetite by providing a "feeling of fullness." However, like glucomannan, guar gum and guar gum preparations have been linked to causing blockage in the esophagus. The water-retaining ability of the gum permits it to swell to 10- to 20-fold and has led to gastrointestinal blockages. Guar gum can also cause large swings in blood glucose (sugar) levels. Diabetic patients should not use these preparations.

Herbal diuretics: Many varieties of herbal diuretics are very commonly found in over-the-counter (OTC) weight loss products and herbal weight-loss products. Most of the diuretics used OTC come from xanthine alkaloids (like caffeine or theobromine). You should avoid preparations that contain juniper seeds (capable of causing renal damage), equistine (neurotoxic—can cause brain damage), and horse tail or shave grass (contain several dangerous ingredients that can lead to convulsions or hyperactivity). Most of the herbal diuretics are not dangerous but can interact with certain drugs (such as, lithium, digoxin, or conventional diuretics such as furosemide or hydrochlorothiazide). Most of the herbal diuretics do not provide enough diuresis (water loss) to be considered effective weight loss aids.

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