An Ounce Of Prevention Is Worth A Pound Of Cure!

What is it? Guarana

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Guarana is a plant named for the Guarani tribe in the Amazon, who used the seeds to brew a drink. Today, guarana seeds are still used as medicine.

Guarana is used for weight loss, to enhance athletic performance, as a stimulant, and to reduce mental and physical fatigue. It is a frequent addition to energy and weight loss products.

Some people also use guarana to treat low blood pressure and chronic fatigue syndrome (CFS), and to prevent malaria and dysentery. It is also used to enhance sexual desire, to increase urine flow, and as an astringent.

Other uses include treatment of ongoing diarrhea, fever, heart problems, headache, joint pain, backache, and heat stress.

In food manufacturing, guarana has been used as a flavoring ingredient in beverages and candy.

How effective is it?

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for GUARANA are as follows:

Insufficient evidence to rate effectiveness for…

  • Anxiety. Early research suggests that taking two tablets of a specific product (Euphytose) containing hawthorn, black horehound, passionflower, valerian, cola nut, and guarana three times daily for 28 days can reduce anxiety in some people. However, it is not clear if guarana alone is beneficial.
  • Mental performance. Early research in healthy people suggests that taking a single dose of guarana dry extract can improve thinking speed. However, other research suggests that taking guarana daily does not improve mental function in adults or older people.
  • Weight loss. Guarana might promote weight loss when used in combination with mate and damiana. There is also developing evidence that a specific combination product containing guarana, ephedra, and 17 other vitamins, minerals, and supplements (Metabolife-356) might help reduce weight by approximately 2.7 kg over eight weeks when used with a low-fat diet and exercise. However, more evidence is needed to rate guarana for this use.
  • Malaria.
  • Diarrhea.
  • Fever.
  • Headaches.
  • Heart problems.
  • Improvement of exercise endurance.
  • Improvement of short-term, high-intensity performance and power.
  • Increasing blood pressure in people who have low blood pressure.
  • Chronic fatigue syndrome (CFS).
  • Joint pain.
  • Fluid retention.
  • Other conditions.

More evidence is needed to rate guarana for these uses.

How does it work?

Guarana contains caffeine. Caffeine works by stimulating the central nervous system (CNS), heart, and muscles. Guarana also contains theophylline and theobromine, which are chemicals similar to caffeine.

Are there safety concerns?

Guarana is LIKELY SAFE for most adults when consumed in amounts commonly found in foods.

Guarana is POSSIBLY SAFE when taken my mouth in medicinal amounts for a short time.

Guarana is POSSIBLY UNSAFE when taking by mouth in high doses for a long time. Doses greater than 250-300 mg daily have been linked to side effects. Side effects depend on the dose. At typical doses, the caffeine in guarana can cause insomnia, nervousness and restlessness, stomach irritation, nausea, vomiting, increased heart rate and blood pressure, rapid breathing, tremors, delirium, diuresis, and other side effects. Large guarana doses might cause headache, anxiety, agitation, ringing in the ears, pain when urinating, stomach cramps, and irregular heartbeats. People who take guarana regularly may experience caffeine withdrawal symptoms if they reduce their usual amount.

Guarana is LIKELY UNSAFE and even deadly, due to its caffeine content, when taken by mouth or injected in very high doses. The fatal dose of caffeine is estimated to be 10-14 grams (150-200 mg per kilogram; the “typical” man weighs about 70 kilograms, so a lethal dose of caffeine for this man would be 10,500-14,000 mg). This is quite a high dose. Consider that one cup of brewed coffee provides from 95-200 mg of caffeine. However, serious poisoning can occur at doses lower than 150-200 mg per kilogram depending on an individual’s caffeine sensitivity or smoking behavior, age, and prior caffeine use.

Special precautions & warnings:

Pregnancy and breast-feeding: Guarana is POSSIBLY SAFE for pregnant and breast feeding women when taken in amounts commonly found in foods. If you are pregnant or breast-feeding, guarana should be taken with caution due to the caffeine content. Small amounts are probably not harmful. However, taking guarana in high doses by mouth is POSSIBLY UNSAFE. Consuming more than 200 mg has been linked to an increased risk of miscarriage and other negative effects.

Anxiety: The caffeine in guarana might make feelings of anxiety worse.

Bleeding disorders: There is some evidence suggesting that the caffeine in guarana might make bleeding disorders worse, although this has not been reported in people. If you have a bleeding disorder, check with your healthcare provider before starting guarana.

Diabetes: Some research suggests that the caffeine in guarana may affect the way people with diabetes process sugar (glucose) and may complicate blood sugar control. There is also some interesting research that suggests caffeine may enhance the warning symptoms of low blood sugar in patients with type 1 diabetes. Some studies show that the symptoms of low blood sugar are more intense when they start in the absence of caffeine, but as low blood sugar continues, symptoms are greater with caffeine. This might increase the ability of diabetic patients to detect and treat low blood sugar. However, the downside is that caffeine might actually increase the number of low-sugar episodes. If you have diabetes, talk with your healthcare provider before starting guarana.

Diarrhea. Guarana contains caffeine. The caffeine in guarana, especially when taken in large amounts, can worsen diarrhea.

Irritable bowel syndrome (IBS): Guarana contains caffeine. The caffeine in guarana, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.

Heart disease: The caffeine in guarana might cause irregular heartbeat in certain people. Use with caution.

High blood pressure: Taking guarana might raise blood pressure in people with high blood pressure due to its caffeine content. However, this effect might be less in people who are regular coffee-drinkers or otherwise use caffeine on a regular basis.

Glaucoma: The caffeine in guarana increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes after drinking caffeinated beverages.

Osteoporosis: The caffeine in guarana can flush calcium out of the body through the kidneys. This calcium loss might help to weaken bones. To minimize this problem, don’t use more than 300 mg of caffeine per day. Taking calcium supplements may also help to offset these calcium losses. Postmenopausal women who have a genetic problem that affects how vitamin D is used by the body should use caffeine with caution.

Are there interactions with medications?

Major
Do not take this combination.
Amphetamines
Stimulant drugs such as amphetamines speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Cocaine
Stimulant drugs such as cocaine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Ephedrine
Stimulant drugs speed up the nervous system. Caffeine (contained in guarana) and ephedrine are both stimulant drugs. Taking guarana along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine-containing products and ephedrine at the same time.
Moderate
Be cautious with this combination.
Adenosine (Adenocard)
Guarana contains caffeine. The caffeine in guarana might block the affects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming guarana or other caffeine-containing products at least 24 hours before a cardiac stress test.
Antibiotics (Quinolone antibiotics)
The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with guarana can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.

Some antibiotics that decrease how quickly the body breaks down caffeine include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar).

Cimetidine (Tagamet)
Guarana contains caffeine. The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with guarana might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.
Clozapine (Clozaril)
The body breaks down clozapine (Clozaril) to get rid of it. The caffeine in guarana seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking guarana along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).
Dipyridamole (Persantine)
Guarana contains caffeine. The caffeine in guarana might block the effects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming guarana or other caffeine-containing products at least 24 hours before a cardiac stress test.
Disulfiram (Antabuse)
The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking guarana (which contains caffeine) along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.
Estrogens
The body breaks down the caffeine in guarana to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking guarana along with estrogens can cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogens, limit your caffeine intake.

Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

Fluvoxamine (Luvox)
The body breaks down the caffeine in guarana to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking guarana along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.
Lithium
You body naturally gets rid of lithium. The caffeine in guarana can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.
Medications for asthma (Beta-adrenergic agonists)
Guarana contains caffeine. Caffeine can stimulate the heart. Some medications for asthma can also stimulate the heart. Taking caffeine with some medications for asthma might cause too much stimulation and cause heart problems.

Some medications for asthma include albuterol (Proventil, Ventolin, Volmax), metaproterenol (Alupent), terbutaline (Bricanyl, Brethine), and isoproterenol (Isuprel).

Medications for depression (MAOIs)
Guarana contains caffeine. Caffeine can stimulate the body. Some medications used for depression can also stimulate the body. Taking guarana with these medications used for depression might cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others.

Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Guarana contains caffeine. Caffeine might slow blood clotting. Taking guarana along with medications that also slow clotting might increase the chances of bruising and bleeding.

Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.

Nicotine
Stimulant drugs such as nicotine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in guarana might also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Pentobarbital (Nembutal)
The stimulant effects of the caffeine in guarana can block the sleep-producing effects of pentobarbital.
Phenylpropanolamine
The caffeine in guarana can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking guarana along with phenylpropanolamine might cause too much stimulation and increase heartbeat, blood pressure and cause nervousness.
Riluzole (Rilutek)
The body breaks down riluzole (Rilutek) to get rid of it. Taking guarana can decrease how fast the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole.
Stimulant drugs
Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heartbeat. Guarana contains caffeine, which can also speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with guarana.

Some stimulant drugs include nicotine, cocaine, sympathomimetic amines, and amphetamines.

Theophylline
Guarana contains caffeine. Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. Taking guarana along with theophylline might increase the effects and side effects of theophylline.
Verapamil (Calan, Covera, Isoptin, Verelan)
The body breaks down the caffeine in guarana to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Taking guarana along with verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of caffeine side effects including jitteriness, headache, and an increased heartbeat.
Minor
Be watchful with this combination.
Alcohol
The body breaks down the caffeine in guarana to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking guarana along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.
Birth control pills (Contraceptive drugs)
The body breaks down the caffeine in guarana to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking guarana along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.

Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.

Fluconazole (Diflucan)
Guarana contains caffeine. The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine Taking guarana along with fluconazole (Diflucan) might increase the risk of caffeine side effects such as nervousness, anxiety, and insomnia.
Medications for diabetes (Antidiabetes drugs)
Guarana might increase blood sugar. Diabetes medications are used to lower blood sugar. By increasing blood sugar, guarana might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

Mexiletine (Mexitil)
Guarana contains caffeine. The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking mexiletine (Mexitil) along with guarana might increase the caffeine effects and side effects of guarana.
Terbinafine (Lamisil)
The body breaks down caffeine (contained in guarana) to get rid of it. Terbinafine (Lamisil) can decrease how fast the body gets rid of caffeine and increase the risk of side effects including jitteriness, headache, increased heartbeat, and other effects.

Are there interactions with herbs and supplements?

Bitter orange
Guarana contains caffeine. Taking bitter orange along with herbs that contain caffeine, such guarana, can increase blood pressure and heart rate in people who otherwise have normal blood pressure. This might increase the chance of developing problems with the heart and blood vessels.
Caffeine-containing herbs and supplements
Guarana contains caffeine. Taking it with other herbs and supplements that also contain caffeine can increase both the harmful and helpful effects of caffeine. Other natural products that contain caffeine include coffee, black tea, green tea, oolong tea, pu-erh tea, mate, and cola.
Calcium
High caffeine intake from foods, beverages, and herbs including guarana increases urinary calcium excretion.
Creatine
There is some concern that combining caffeine, ephedra, and creatine might increase the risk of serious side effects. There is a report of stroke in an athlete who took 6 grams of creatine monohydrate, 400-600 mg of caffeine, 40-60 mg of ephedra, and a variety of other supplements daily for 6 weeks. Caffeine might also decrease creatine’s possible beneficial effects on athletic performance.
Ephedra (Ma huang)
Ephedra is a stimulant. Guarana is a stimulant, due to it’s caffeine content. Using ephedra along with guarana can cause too much stimulation in the body. One unpublished report linked jitteriness, high blood pressure, seizures, temporary loss of consciousness, and hospitalization requiring life support with the use of a combination ephedra and guarana (caffeine) product. Don’t take guarana with ephedra or other stimulants.
Herbs and supplements that slow blood clotting (Anticoagulant/Antiplatelet herbs and supplements
Guarana seems to be able to slow blood clotting. Using it along with other herbs and supplements that also slow blood clotting might increase the risk of bleeding in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, and Panax ginseng.
Magnesium
High caffeine intake from foods, beverages, and herbs including guarana increases urinary magnesium excretion.

Are there interactions with foods?

There are no known interactions with foods.

What dose is used?

The appropriate dose of guarana depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for guarana. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Methodology

To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.

References

  1. Brice C and Smith A. The effects of caffeine on simulated driving, subjective alertness and sustained attention. Hum Psychopharmacol Clin Exp 2001;16:523-531.
  2. Neims AH, Bailey J, and Aldridge A. Disposition of caffeine during and after pregnancy. Clin Res 1979;27:236A.
  3. Johnsen O, Eliasson R, and Abdel-Kadar MM. Effects of caffeine on the motility and metabolism of human spermatozoa. Andrologia 1974;6:53-58.
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