A type of supplement known as the "dopamine bean" can contain very high levels of levodopa -- in some cases, higher than prescription formulations used to treat Parkinson's disease, researchers found.
Among 15 brands of Mucuna pruriens supplements, levodopa content ranged from 2 mg to 241 mg, and the latter amount was close to the maximum dosage of prescription levodopa available, which ranges from 50- to 250-mg doses, Pieter Cohen, MD, of Cambridge Health Alliance in Massachusetts, and colleagues reported in a research letter in JAMA Neurology.
Cohen said the high doses of levodopa found in these supplements "pose direct challenges to managing patients with Parkinson's disease who are using these supplements. The dose of levodopa the patient is receiving would be much greater than what we think the patient is using based on our prescribed medications."
Outside of Parkinson's disease, people who use them solely for their dopaminergic effects could experience a "wide variety of serious side effects including paranoia and psychosis," Cohen told MedPage Today.
Cohen said he and his team began investigating Mucuna supplements after concerned parents said they believed their son was having serious psychiatric effects from the products and wouldn't stop using them.
Mucuna supplements are "marketed from Amazon to Vitamin Shoppe for their dopamine effects, to help with mood, workouts, focus, energy -- you name it," Cohen said. The natural bean does contain small amounts of the dopamine precursor levodopa.
How commonly Mucuna is used in the U.S. isn't known, but the researchers cited a recent survey of 205 patients with Parkinson's disease finding that 7% of those who used supplements were taking Mucuna products.
To further their previous work investigating how "botanical" supplements are actually formulated as potent drugs, Cohen and colleagues searched the NIH Dietary Supplement Label Database in November 2021 to identify supplements with Mucuna pruriens on the label. They purchased online the 20 brands most recently added to the database in 2021.
They also obtained two samples of Mucuna pruriens seeds from the National Center for Natural Products Research repository at the University of Mississippi to determine the amount of levodopa in seed extract.
Ultimately, of the 20 samples, one wasn't available, one was a duplicate entry, and two did not have both "Mucuna pruriens" and "dietary supplement" on the label, so the researchers ended up with 16 products. Of these, one product contained no detectable levels of levodopa.
For Mucuna seed extract, authenticated samples contained 2.5% to 3.9% levodopa. But among Mucuna supplements that listed a specific quantity of seed extract on the label, the actual quantity of levodopa was 228% to 2,186% greater than the estimated quantity.
The researchers warned that it's not possible to directly compare the pharmacologic effects of levodopa in Mucuna supplements with prescription levodopa because pharmaceutical versions include a peripheral decarboxylase inhibitor -- which limits conversion of levodopa to dopamine -- that is not present in Mucuna supplements.
Cohen told MedPage Today that side effects will be "very hard to predict," as it will "depend on how much of the levodopa in these supplements enters the central nervous system." Nonetheless, he said, excess dopamine "can lead to a wide range of adverse effects including agitation, impulse control disorders, peripheral neuropathies, and orthostatic hypotension."
The researchers noted their study was limited because they only analyzed two samples of seed extract, so it's possible that other variants of Mucuna pruriens or different extraction methods may affect the quantity of levodopa. Also, only one sample from each supplement brand was analyzed, so it's unknown whether levodopa doses vary from batch to batch.
Still, they concluded that "clinicians may identify unsuspected levodopa consumption by asking patients about the use of supplements and advising that consumption of M. pruriens supplements may unpredictably complicate the management of Parkinson's and other diseases."
Disclosures
Cohen reported receiving grants from The Pew Charitable Trusts and Consumers Union and being the subject of a civil suit brought by Hi-Tech Pharmaceuticals, a supplement company (the jury found in Cohen's favor), both outside the submitted work.
