What are L-tyrosine’s main drawbacks?

Although L-tyrosine has shown beneficial effects in some studies, it has a mixed track record for efficacy, with some studies failing to observe positive effects on cognition.^[1][2] This may be partially explained by the fact that L-tyrosine increases catecholamine synthesis only when catecholamine levels are depleted, limiting efficacy to sufficiently stressful or challenging conditions. Efficacy may also vary in different individuals, as highlighted by one study that found that the effects of L-tyrosine on cognitive function become detrimental with older age.^[1] There are also possible contraindications for L-tyrosine supplementation in people with hyperthyroidism or anyone taking L-dopa or monoamine oxidase inhibitors. If this applies to you, consult with your physician before supplementing with L-tyrosine.