How Does Tryptophan Affect ADHD Symptoms?

What you need to know

• Tryptophan is an amino acid found in protein-rich foods that may affect brain chemistry and behavior.
• Studies have looked at how changing tryptophan levels impacts symptoms in people with ADHD.
• Lowering tryptophan may increase aggression in some people with ADHD, but effects on core ADHD symptoms are unclear.
• More research is needed before dietary changes involving tryptophan can be recommended for ADHD.

What is tryptophan and how might it relate to ADHD?

Attention deficit hyperactivity disorder (ADHD) is a common condition that affects both children and adults. People with ADHD often struggle with inattention, hyperactivity, and impulsivity. While medications can be effective for many, there is interest in other approaches that may help manage symptoms, including dietary changes.

One dietary component that has attracted interest is an amino acid called tryptophan. Tryptophan is found in protein-rich foods like turkey, chicken, fish, eggs, and nuts. In the body, tryptophan can be converted into serotonin, an important brain chemical involved in mood and behavior regulation.

Some researchers have wondered if tryptophan levels may impact ADHD symptoms by affecting serotonin in the brain. To explore this, studies have looked at what happens when tryptophan levels are experimentally lowered in people with ADHD.

How do researchers study tryptophan’s effects?

To study how tryptophan impacts the brain and behavior, researchers use a technique called acute tryptophan depletion (ATD). This involves giving participants a drink containing amino acids but lacking tryptophan. This causes a temporary drop in tryptophan levels in the body and brain.

Researchers then compare how people perform on various cognitive and behavioral tests when their tryptophan levels are lowered versus normal. This allows them to see if changing tryptophan has any measurable effects.

What have studies on tryptophan and ADHD found?

A systematic review by Dinu and colleagues examined 14 studies that used tryptophan depletion in people with ADHD. Here are some key findings:

Effects on core ADHD symptoms

Surprisingly, most studies did not focus on measuring the core symptoms of ADHD - inattention, hyperactivity, and impulsivity. The few that did look at attention and impulsivity found mixed results, with tryptophan depletion sometimes improving and sometimes worsening performance. No studies examined effects on hyperactivity.

Effects on aggression

The most consistent finding was that lowering tryptophan levels appeared to increase aggressive behavior in some people with ADHD, particularly when provoked. Multiple studies found participants were quicker to react aggressively after tryptophan depletion.

Other effects

Individual studies looked at various other outcomes, including:

• Mood - No clear effects were found
• Memory - No significant impacts on verbal memory
• Brain activity - Some changes in connectivity between brain regions were observed

Limitations of the research

While these studies provide some intriguing clues, there are important limitations to keep in mind:

• Most studies had small sample sizes, with less than 25 participants.
• Nearly all participants were male children or adolescents. Very few studies included females or adults.
• All the research was conducted by one research group in Germany, limiting how widely the findings can be applied.
• The studies only looked at lowering tryptophan levels, not increasing them through diet or supplements.
• Many studies allowed participants with other conditions like conduct disorder, which could influence the results.

What does this mean for people with ADHD?

Based on the current evidence, it’s too early to make any recommendations about changing tryptophan intake for people with ADHD. The research so far is limited and has focused mainly on temporarily depleting tryptophan rather than increasing it.

The most consistent finding - that lowering tryptophan may increase aggression - suggests that having adequate tryptophan in the diet could potentially help reduce aggressive behavior in some people with ADHD. However, this needs to be studied directly before any conclusions can be drawn.

More research is clearly needed, particularly studies that:

• Include more female participants and adults with ADHD
• Examine effects of increasing tryptophan through diet or supplements
• Focus on measuring core ADHD symptoms
• Have larger sample sizes and are conducted by different research groups

Conclusions

• Changing tryptophan levels may impact some behaviors in people with ADHD, particularly aggression.
• Effects on core ADHD symptoms like inattention and hyperactivity remain unclear.
• More high-quality research is needed before dietary changes involving tryptophan can be recommended for ADHD.
• People with ADHD should consult their doctor before making any major changes to their diet or trying supplements.