Feeling blue? Mung beans, lobster, turkey, asparagus, sunflower seeds, cottage cheese, pineapple, tofu, spinach and bananas could lift your spirits.

A diet high in tryptophan - an amino acid converted by the body into the feel-good chemical serotonin - can improve mood and wellbeing, pediatrician and natural health expert Caroline Longmore said.

The body cannot produce tryptophan so unless we get enough through our diets, we may suffer a deficiency, leading to low serotonin levels which are associated with mood disorders, anxiety, cravings and irritable bowel syndrome (IBS).

"Following a diet which contains foods rich in naturally occurring serotonin will improve your mood, leaving you energised and in a state of harmony and wellbeing," Dr Longmore said.

Mental health experts say while the theory behind tryptophans for improving mood is solid, its use by depressed patients has a chequered history in Australia.

Gordon Parker, from the Black Dog Institute, said tryptophan supplements were widely used before the 1990s but after a number of patients suffered serious side effects from a contaminated batch, they were temporarily taken off the market.

Professor Parker said while some patients strongly believed such supplements were beneficial, scientific evidence was lacking.

"I would say it's something that can be useful for some people but the quality control varies enormously," he said.

In her ebook The Serotonin Secret, Dr Longmore claims the best way to get optimum tryptophan levels is through a carefully devised eating plan. She rates dozens of foods for their levels of tryptophan.

Written with Australian-trained medical scientist and naturopath Katrin Hempel, the book has 50 recipes designed to solve serotonin imbalance without drugs. The concept works on the same principle as selective serotonin re-uptake inhibitors (SSRIs), such as popular antidepressant Prozac.

Britain's Food and Mood Project recommends eating chicken, sardines, turkey, salmon, fresh tuna, nuts and seeds to boost serotonin levels.

But Associate Professor Michael Baigent, clinical adviser to Beyondblue, said there was only low-level evidence to suggest tryptophans have a medical effect.

(China Daily/Agencies May 16,2008)