Vitamins and minerals could be useful for treating ADHD, research suggests.
Adults with ADHD given supplements for eight weeks had a "modest" improvement in concentration span, hyperactivity, and other symptoms, a small-scale study found.
A wide range of nutrients, including vitamin D, iron and calcium, may improve brain functioning, said psychologists in New Zealand.
Another study found medication reduced road accidents in men with ADHD.
As many as one in 20 adults has ADHD (attention-deficit hyperactivity disorder), marked by symptoms such as lack of attention, concentration difficulties and impulsiveness.
ADHD can be treated with medications, such as central nervous system stimulants, which affect the brain and improve symptoms.
According to the research, published in The British Journal of Psychiatry, taking a broad range of vitamins and minerals may also help reduce ADHD symptoms.
In the study, 80 adults with ADHD were given either supplements containing vitamin D, vitamin B12, folate, magnesium, ferritin, iron, calcium, zinc and copper, or a dummy pill.
After eight weeks of treatment those on supplements reported greater improvements in both their inattention and hyperactivity/impulsivity compared with those taking the placebo.
Psychologists from the University of Canterbury, in Christchurch, say the effects of vitamins and minerals (micronutrients) are more modest than medication but may be useful for some people, particularly those seeking alternative treatments.
"Our study provides preliminary evidence of the effectiveness for micronutrients in the treatment of ADHD symptoms in adults," said Prof Julia Rucklidge, who led the study.
"This could open up treatment options for people with ADHD who may not tolerate medications, or do not respond to first-line treatments."
Philip Asherson, professor in molecular psychiatry at the Institute of Psychiatry in London, said the suggestion that vitamins and minerals improved brain metabolism was intriguing but needed further investigation.
"It's a good study, which is very interesting, but really needs replicating," he told the BBC. "The mechanisms behind it remain unclear."
Meanwhile, a separate study on ADHD in Sweden suggests medication could save lives on the road.
Research indicated almost half of transport accidents involving men with ADHD could be avoided if they were taking medication for their condition.
Scientists from the Karolinska Institute studied 17,000 individuals with ADHD over a period of four years using data from health registers.
They found individuals with ADHD had a higher risk of being involved in serious transport accidents, such as car or motorcycle crashes, compared with those without ADHD.
Transport accidents were lower among men with ADHD who were on medication than among men with ADHD who did not take medication.
Calculations showed 41% of transport accidents involving men with ADHD could have been avoided if they had received medication and carried on taking it during the course of the study.
A similar effect was not found in women.
"Even though many people with ADHD are doing well, our results indicate that the disorder may have very serious consequences," said Henrik Larsson, associate professor at the Department of Medical Epidemiology and Biostatistics.
"Our study also demonstrates in several different ways that the risk of transport accidents in adult men with ADHD decreases markedly if their condition is treated with medication."
The research is published in the journal JAMA Psychiatry.