L-Dopa is a precursor to dopamine that can cross the blood-brain barrier. Widely marketed as levodopa, it is used to treat Parkinson's Disease; wherein dopaminergic neurons are non-functional or killed. DOPA decarboxylase converts L-Dopa to dopamine.
##Molecular Effects of L-Dopa
L-Dopa has been shown to interact with some hormone pathways, including androgens (testosterone), growth hormone, luteinizing hormone, and cortisol.1,2,3,4However, this literature is sparse so few conclusions can be drawn. But interestingly, several studies have investigated the influence of L-Dopa on libido, demonstrating that hormonal modulation by L-dopa may have a functional effect. In particular, it was found that levodopa therapy in Parkinson's disease might lead to hypersexuality. Furthermore, in healthy man, one dose of 100 mg of L-Dopa modulated the T-reflex, a measure of sexual stimulation.5These data indicate that L-Dopa administration, even in healthy adults, can have important consequences on hormone signaling pathways and sexuality. However, these effects have not been well-studied.
In a placebo-controlled study of 40 healthy humans, administration of 100 mg of L-dopa (in the form of levodopa), per day for five days, significantly increased the speed, accuracy, and long-term memory consolidation in a novel word learning paradigm.6
Due to its wide use as a pharmaceutical, L-Dopa has been extensively studied. L-Dopa is not generally regarded as safe (GRAS) by the FDA and therefore we do not recommend its supplementation as a nootropic. L-Dopa has undesirable side effects that have been well-profiled in patients taking high doses of L-Dopa, however, the severity and frequency of these side effects have not been evaluated in healthy adults, at any dose. Additionally, there is only one study that has investigated the nootropic benefits of L-Dopa, more studies are required before an effect of cognitive enhancement can be confirmed.
Yamada, T., Nakamura, J., Murakami, M., Okuno, Y., Hosokawa, S., Matsuo, M., & Yamada, H. (1995). Effect of chronic L-dopa administration on serum luteinizing hormone levels in male rats. Toxicology, 97(1-3), 173-182.
Prasad, S. K., Qureshi, T. N., & Qureshi, S. (2009). Mucuna pruriens seed powder feeding influences reproductive conditions and development in Japanese quail Coturnix coturnix japonica. Animal, 3(2), 261-268. doi:10.1017/s175173110800339x
Muller, T., Welnic, J., & Muhlack, S. (2007). Acute levodopa administration reduces cortisol release in patients with Parkinson's disease. J Neural Transm (Vienna), 114(3), 347-350. doi:10.1007/s00702-006-0552-0
Knecht, S., Breitenstein, C., Bushuven, S., Wailke, S., Kamping, S., Floel, A., . . . Ringelstein, E. B. (2004). Levodopa: faster and better word learning in normal humans. Ann Neurol, 56(1), 20-26. doi:10.1002/ana.20125
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