From the Guidelines
Consuming excessive tryptophan from protein sources is unlikely to cause significant adverse effects, as the amounts found in regular dietary protein consumption are generally not enough to cause harm. Tryptophan is an essential amino acid found in protein-rich foods like turkey, chicken, eggs, and dairy products. While tryptophan is a precursor to serotonin and melatonin, which can promote relaxation and sleepiness, the evidence suggests that dietary protein intake should be reasonably proportional to carbohydrate and fat intake, with an average of 50 to 100 g/d of protein recommended 1. The American Heart Association recommends that total protein intake should not be excessive and should be part of a balanced eating plan that supports weight maintenance and lowers chronic disease risk 1. Additionally, a study on dietary supplements suggests that L-tryptophan may cause CNS depression, but due to its rapid metabolism, it may be held for 24 hours before surgery, implying that its effects are short-lived 1. Therefore, it is unlikely that excessive tryptophan from protein intake will cause significant adverse effects, and individuals should focus on overall healthy eating patterns, adequate sleep, and a balanced lifestyle to maintain their health and well-being. Some key considerations for a healthy diet include:
- Consuming a variety of protein-rich foods as part of a balanced diet
- Avoiding excessive protein intake, which can impose a metabolic burden on the kidneys and liver 1
- Ensuring adequate carbohydrate and fat intake to support overall nutritional adequacy
- Staying hydrated and taking breaks during long periods of physical or mental activity to maintain alertness and focus.
From the Research
Adverse Effects of Excessive Tryptophan Intake
- There is evidence to suggest that excessive tryptophan intake may have adverse effects on mood and cognition 2.
- High levels of tryptophan intake have been associated with impaired cognition, while moderate to high levels have been shown to improve cognition 2.
- The relationship between tryptophan intake and mood is complex, with an inverted U-shaped curve suggesting that both low and high levels of tryptophan may impair mood, while moderate levels may improve mood 2.
Tryptophan Intake and Human Health
- Tryptophan is an essential amino acid that plays a crucial role in many metabolic functions, including the synthesis of serotonin and melatonin 3.
- Tryptophan supplementation has been considered as a treatment for depression, sleep disorders, and cognitive disorders, due to its relationship with serotonin synthesis 3, 4.
- A systematic review of randomized controlled trials found that tryptophan supplementation may be effective in improving mood and reducing anxiety in healthy individuals 4.
Safety of Tryptophan Intake
- A study of tryptophan intake in the US adult population found that usual intake levels were several times higher than the estimated average requirement, but were not associated with abnormal laboratory findings or adverse effects on liver or kidney function 5.
- The study found that tryptophan intake was inversely associated with self-reported depression and positively associated with sleep duration, suggesting that tryptophan intake may have beneficial effects on mood and sleep outcomes 5.