5-HTP supplements have become a familiar sight in health stores and pharmacies, promoted as a natural way to improve mood. The amino acid is produced by the body and is being marketed as a shortcut to serotonin, sometimes called the happiness hormone.

That appealing description leaves out important questions about effectiveness and safety. As with other wellness trends, the evidence behind 5-HTP is more complicated than the confident marketing language may suggest.

Registered dietitian Dr Sammie Gill, a senior nutrition scientist at the British Nutrition Foundation, explains that understanding the supplement begins with serotonin and the process the body uses to produce it.

“Serotonin (chemical name: 5-hydroxytryptamine or 5-HT) is a neurotransmitter – a type of hormone known for its effect on mood,” Dr Gill explains. “Serotonin also helps regulate the function of major organs, including the heart and gut.”

The body does not create serotonin in a single step. It first converts tryptophan, an essential amino acid found in food, into 5-HTP before converting the resulting compound into serotonin.

“The body produces serotonin by first converting the essential amino acid tryptophan – found in food – into 5-hydroxytryptophan (5-HTP), which is then converted into serotonin,” says Dr Gill. That makes 5-HTP the direct chemical building block used by the body to make serotonin.

Because 5-HTP is a direct precursor to serotonin, supplements have been promoted as a more direct option than tryptophan. The sales pitch rests on the idea that taking 5-HTP skips the tryptophan stage and therefore offers a shortcut to serotonin production.

Dr Gill believes the supplement’s current online popularity may reflect growing awareness of mental health disorders. That awareness may be encouraging people to seek nonmedical options for mental health support, while the wellness industry remains focused on optimizing mood and sleep.

Some 5-HTP used in supplements comes from a plant source. “The seeds of Griffonia simplicifolia – a shrub native to west Africa – are naturally rich in 5-HTP and commonly used in supplements,” says Dr Gill.

Those seeds are not something people would casually eat, but the body can make 5-HTP from dietary tryptophan. Dr Gill identifies dairy, fish, meat, nuts, seeds and whole grains as food sources of that essential amino acid.

Research has suggested that 5-HTP supplementation may offer benefits for mood, sleep and appetite regulation. However, Dr Gill cautions that many of the studies supporting those possibilities are small, conducted in animals, or both.

One randomized controlled trial did report improvements in cognitive performance and depressive symptoms among people taking 5-HTP compared with those who were not. Dr Gill notes that this type of trial is considered a gold standard study design.

Even so, a single encouraging trial does not resolve the broader uncertainties described by Dr Gill. She says there remain “a lot of unknowns, including the ideal dosage and which types of depression may be most likely to benefit from 5-HTP”.

Safety is another major consideration, particularly for people already taking medication. Dr Gill stresses that anyone considering 5-HTP should speak with a healthcare professional before beginning supplementation.

That consultation is especially important for people taking antidepressants such as selective serotonin reuptake inhibitors, commonly known as SSRIs. Combining them with 5-HTP carries a known risk linked to excessive serotonin.

Dr Gill advises caution “because of 5-HTP’s known risk of causing serotonin syndrome – a potentially serious condition resulting from excess serotonin.” The warning sharply complicates the supplement’s image as a simple or universally safe natural mood booster.

The available information therefore presents a mixed picture. Although some research suggests possible benefits and one randomized controlled trial reported improvements, unresolved questions remain about dosage, effectiveness for different types of depression and the risk for people taking antidepressants.