Yohimbe, derived from the bark of the African evergreen tree Pausinystalia yohimbe, has gained popularity as a dietary supplement touted for its potential to treat erectile dysfunction and promote fat loss. While yohimbe and its active ingredient, yohimbine, have a long history of use in traditional West African medicine, it is crucial to approach this supplement with caution. This article delves into the scientific studies surrounding yohimbine, its potential benefits, associated risks, and important considerations for its use.
What is Yohimbine?
Yohimbe is an herbal supplement sourced from the bark of the Pausinystalia yohimbe tree, native to western and central Africa. It is available in capsule or tablet form, often marketed as yohimbe bark extract or yohimbine. Yohimbine is the main active ingredient in yohimbe supplements. This herbal medicine has been used traditionally in Africa for various health conditions, including cough, fever, and heart disease. In Western countries, yohimbe has been explored as a treatment for sexual dysfunction and included in herbal supplements for weight loss.
Yohimbine, also known as aphordine, corynine, hydroaergotocin, and quebrachine, is an alkaloid found primarily in the Pausinystalia yohimbe tree. It can also be found in Rauwolfia Serpentina and other plants within the Rauwolfia family.
Yohimbine exists as one molecule with three diastereoisomers. The four molecules that tend to exist together in sources of Yohimbine are yohimbine, 3-epi-α-yohimbine, corynanthine, and rauwolscine. Of these, 3-epi-α-yohimbine appears structurally similar to Reserpine (a molecule in Rauwolfia Serpentina) and does not interact highly with the alpha-adrenergic receptors, which is seen as yohimbine's main mechanism of action.
Yohimbine HCl has a molecular weight of 390.87g and a boiling point of 302°C/575.6°F. It is recommended to store Yohimbine HCl in a dry, cool place, as it is deemed stable under these conditions. Yohimbine may be sensitive to excessive light, similar to structurally related alkaloids. Yohimbine is a crystalline white powder.
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Potential Benefits of Yohimbine
Treating Erectile Dysfunction
Yohimbine is thought to help alleviate erectile dysfunction by stimulating alpha-2 adrenergic receptors, which play a role in preventing erections. A 2021 systematic review suggested that Yohimbe shows promising results as a natural supplement for erectile dysfunction, especially when combined with other treatments. However, further research is needed to confirm the effectiveness of Yohimbe supplements for treating erectile dysfunction.
Yohimbine, due to its alpha-2-adrenergic inhibitory potential, was commonly used as a first-line treatment for erectile dysfunction before the advent of PDE5 inhibitors. A review noted a variable efficacy range of 34-73%, possibly due to its effectiveness in individuals with psychogenic erectile dysfunction rather than other forms, such as organic erectile dysfunction.
Combination therapy of Yohimbine with L-Arginine has shown preliminary benefits, with more efficacy in mild to moderate erectile dysfunction.
Aiding Weight Loss
Yohimbe supplements are often marketed for their potential to aid weight loss and improve body composition. Some animal studies have shown modest weight reductions with yohimbine supplementation, particularly when combined with exercise and dietary modifications. However, more research in humans is needed to determine whether Yohimbe can affect weight loss.
Yohimbine acts upon the adrenergic receptor system of fat cells, which regulates thermogenesis. The beta-subunits of the adrenergic receptors can be seen as stimulatory for fat loss as they increase the activity of the enzyme Adenyl Cyclase and subsequently cAMP levels. The alpha-subunits are more suppressive of fat metabolism, in which their activation reduces activity of Adenyl Cyclase and reduces cAMP levels (specifically alpha-2). Beyond being an 'Alpha-Adrenergic antagonist', yohimbine has selectivity for the Alpha-2C subunit more than other subunits.
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Ketogenesis, or the production of ketone bodies, is enhanced under the presence of noradrenaline under normal conditions. Blocking the alpha adrenergic receptors, via the blocking of the alpha-2 adrenergic receptor, augments the ketogenic effects of noradrenaline.
However, at least one study has noted null results, in that yohimbine did not decrease weight in healthy volunteers.
One study in elite soccer players noted that, after 21 days of supplementation at 20mg daily (two doses of 10mg), no influence was found on lean mass nor exercise performance despite a decrease in fat mass.
Other Potential Benefits
- Interactions with Sexuality: Yohimbine can reverse the anti-aphrodisiac effects of alpha-2-adrenergic agonists in rats or can negate some chemicals that antagonize sexuality, while enhancing sexual motivation in otherwise healthy rats.
- Anxiety Reduction: The increase in anxiety associated with yohimbine can be abolished by diazepam (anxiolytic sedative) and clonidine (activator of the A2A receptor that yohimbine inhibits). The increase in anxiety still exists but to a lesser degree in persons with good aerobic fitness, such as marathon runners.
- Cognitive Performance: In persons with low baseline anxiety, 15 mg yohimbine is associated with an increase in arithmetic task performance secondary to its ability to increase arousal.
- Cerebral Blood Flow: Yohimbine reduced cerebral blood flow in most subjects, but one subject who had a minor panic attack experienced an increase in blood flow.
- Fear Extinction: Yohimbine appears to play a role in facilitating fear extinction, which is a psychological phenomena where repeated exposures to a fearful stimuli eventually results in desensitization to the stimuli and less fear associated with it.
- Orthostatic Hypotension: Yohimbine appears to be capable of enhancing sympathetic tone due to its ability to increase blood pressure and is a more potent treatment of orthostatic hypotension than pyridostigmine when yohimbine is used at 5.4mg.
- Hormone Interactions: The increase in sexual desire seen from Yohimbine does not appear to be related to testosterone, although at least one human study has noted that the response to pro-erectile properties of yohimbine is weakly associated with free testosterone.
Risks and Side Effects
Inaccurate Labeling
Dietary supplements are not strictly regulated by the FDA, so there is no guarantee that the product you are getting is exactly what is on the label. This is highly concerning because it puts you at an increased risk of taking a higher dose of this supplement than you intended, which could lead to harmful side effects.
Studies have revealed several cases of inaccurate labeling on yohimbe products. One study of 49 supplements purchased in the US which claimed to contain yohimbine found that the actual dose ranged from 0 to 12.9 mg per recommended serving. The latter dose is greater than the highest prescription strength dose formally available in the US. Furthermore, the actual dose in supplements that contained yohimbine and had a dose on the label was 23-147% of that listed on the supplement, and only 22% of the supplements listed the quantity of yohimbine at all.
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Adverse Effects
Taking yohimbe supplements comes with the risk of several potentially dangerous side effects. The NCCIH states that side effects can include:
- Heart attacks
- Seizures
- Stomach problems
- Tachycardia (a rapid heart rate)
- Anxiety
- High blood pressure
Other adverse effects for yohimbine occur even at recommended dosages, including nausea, abdominal pain, dizziness, and nervousness.
Contraindications
People with a history of heart disease and high or low blood pressure should not take yohimbe. In addition, people with mental health conditions should not take yohimbe as it can interact with certain types of antidepressant medications. Pregnant people and children under the age of 18 years should also refrain from using yohimbe.
Drug Interactions
Yohimbine interacts with the CYP2D6 enzyme and can inhibit its function.
Yohimbine appears to synergistically enhance the pro-erectile effects of Viagra.
Yohimbine and Sibutramine has the potential to interact as the side-effects of Sibutramine are mediated via adrenaline and yohimbine can increase systemic adrenaline levels.
In anaesthetised rats given intravenous Methylphenidate (MPH) to test its effects on neuronal firing, the activation of firing in the prefrontal cortex appears to be augmented under the influence of alpha-2-adrenergic antagonism by yohimbine (1mg/kg).
Relative to consuming Ephedrine at 25mg and Caffeine at 200mg (components of the ECA stack), adding Yohimbine at 5mg appears to attenuate cardiac work at rest, but augment cardiac work during exercise in obese women.
Alcohol also appears to increase noradrenaline levels, and 1.1mL/kg of 95% ethanol (100-120mg/dL BAC) appears to increase noradrenaline (measured via serum MHPG) to a greater level than does 0.4mg/kg yohimbine (double the usual dose); they had additive effects on increasing serum MHPG yet alcohol attenuated the increase of sitting blood pressure nonsignificantly. Despite the higher levels or MHPG with alcohol, subjective anxiety was greater with Yohimbine while alcohol had no effect on yohimbine-induced cortisol spikes.
Dosage and Administration
Total daily dosages of 0.2mg/kg bodyweight have been successfully used to increase fat burning without significant implications on cardiovascular parameters like heart rate and blood pressure. These total daily doses are often divided and taken in two to four doses throughout the day. Caution should be exercised at higher body weight, since the cardiovascular system may not be prepared to handle a stimulatory agent such as yohimbine. Caution should also be exercised since many supplements containing yohimbine either do not list how much yohimbine is included, or if they do, the actual dose ranges from 25-150% of the dose listed. When pairing yohimbine with other stimulatory agents, half-dose both supplements and work up to the recommended dose cautiously, as two supplements can interact negatively.
Adverse drug events in persons taking the recommended dosage (for erectile dysfunction, 5.4mg thrice a day) include nausea, abdominal pain, dizziness, and nervousness. Higher acute dosages in the 15-20mg range some persons may experience tachycardia (irregular heartbeat) and hypertension.
Precautions and Recommendations
Overall, because of the prevalence of inaccurate labeling and potential side effects, it may be safest to avoid this supplement altogether. If you do decide to take yohimbe supplements, buy from a reputable company. It’s best to choose products that have gone through independent third-party testing. This helps verify that the supplements contain what they say they do and in the listed amounts.