Research review
L-tyrosine: what the research does and doesn't show
L-tyrosine's cognitive-performance, dosage and safety research is covered in depth elsewhere on this site. This page rounds up what the same trials do and don't say about weight gain, pregnancy, teenagers and children — groups none of the trials included.
L-tyrosine's main cognitive-performance, dosage, and safety research is covered in depth elsewhere on this site. This page rounds up what the same trial literature does and doesn't say about a few narrower questions: weight gain, pregnancy, teenagers and children.
What the evidence doesn't support
It doesn't support L-tyrosine as a cause of weight gain, and — a separate question — it doesn't support L-tyrosine as a weight-loss aid either (see does L-tyrosine help with weight loss? for that side of it). It doesn't support any specific guidance for pregnancy, breastfeeding, teenagers or children, because none of the trials behind L-tyrosine's evidence included any of those groups.
What the trials found
None of the controlled trials reviewed across this site's L-tyrosine content reported weight gain as a side effect, at doses ranging from single 100-150 mg/kg loading doses up to a sustained 2 g/day over 5 days, and up to 100 mg/kg/day over 4 weeks in a depression trial. That's an absence across the trials that exist, not a comprehensive safety survey of everyone who takes tyrosine.
Every trial behind L-tyrosine's research — the noise-stress, sleep-loss, cold-and-altitude, military-training and depression trials covered on L-tyrosine benefits and who should not take L-tyrosine — enrolled adults. None included pregnant or breastfeeding people, and none included children or teenagers, so there's no dose or safety data specific to any of those groups.
Questions people ask
Can L-tyrosine cause weight gain?
No trial reviewed on this site has reported it as a side effect. See does L-tyrosine help with weight loss? for what the research says about the opposite question.
Can you take L-tyrosine while pregnant?
No published safety data exists for L-tyrosine in pregnancy — every trial behind its research enrolled non-pregnant adults. Ask a doctor before taking any supplement while pregnant.
Is L-tyrosine safe during pregnancy?
Same answer: there's no trial data either way, because pregnant people weren't included in the research. That's an absence of data, not a finding of safety or danger.
Is L-tyrosine safe for kids?
No trial we reviewed included children. There's no dose or safety data for that age group, so there's nothing research-based to base a children's dose on. Ask a doctor before giving a child any supplement not specifically formulated and dosed for them.
Is L-tyrosine safe for teens?
Same gap: no trial we reviewed included adolescents. Ask a doctor before giving a teenager a supplement that hasn't been tested in that age group.
When to talk to a doctor
L-tyrosine is not a treatment for weight gain or weight loss. If you're pregnant, breastfeeding, or considering a supplement for a child or teenager, talk to a doctor first — see L-tyrosine and medications: what to check.
Related reading: L-tyrosine benefits: what the research does and doesn't show, does L-tyrosine help with weight loss?, and who should not take L-tyrosine?.
Sources
- Tyrosine for depression: a double-blind trial A 1990 double-blind trial gave 65 outpatients with major depression 100 mg/kg/day of L-tyrosine or placebo for 4 weeks; tyrosine raised a norepinephrine breakdown product in urine but showed no evidence of antidepressant activity over placebo.
- Effect of tyrosine on cognitive function and blood pressure under stress A 1994 crossover trial in 16 healthy adults found a single 100 mg/kg dose of tyrosine improved performance on two stress-sensitive cognitive tasks under noise stress, with a brief, early dip in diastolic blood pressure and no effect on mood, systolic blood pressure or heart rate.
- Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course A 1999 field trial gave 21 military cadets either 2 g/day of tyrosine or a calorie-matched carbohydrate drink for 5 days during a combat training course; the tyrosine group performed better on memory and tracking tasks and had lower systolic blood pressure, with no difference in mood.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.