Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral condition. Characterized by inattention and/or hyperactive or impulsive behavior that interferes with functioning, learning, or development, ADHD affects as many as 7 percent of children and nearly 3 percent of adults worldwide. Findings from a study published earlier this year suggest that vitamin D and magnesium co-supplementation improves behavior and mental health in children with ADHD.

A growing body of evidence suggests that nutritional inadequacies play critical roles in neurobehavioral and neuropsychiatric conditions, including ADHD, autism spectrum disorder, bipolar disorder, and schizophrenia. A common feature of these disorders is dysfunction of the body’s serotonin pathway. Serotonin is a neurotransmitter and hormone produced in the brain. It regulates social cognition (how people interact socially) and influences decision making. Serotonin levels are often diminished in people who have neurobehavioral or neuropsychiatric disorders.

Vitamin D is a steroid hormone produced in the body in response to ultraviolet light exposure. Its synthesis relies on the activity of six enzymes that catalyze the various reactions in the pathways that activate or deactivate the vitamin. Ultimately, these enzymes modulate the extent of vitamin D-dependent gene expression in the body as well as vitamin D’s participation in various biological pathways. All of these enzymes are magnesium dependent, and evidence suggests that magnesium deficiency impairs vitamin D metabolism. Vitamin D influences serotonin synthesis via its actions on tryptophan hydroxylase 2, a rate-limiting enzyme involved in serotonin production. Interestingly, scientists have identified several tryptophan hydroxylase 2 gene variants associated with ADHD.

The marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) also play roles in serotonin pathways. EPA increases serotonin release by reducing certain types of prostaglandins (proinflammatory molecules). DHA modulates serotonin action by increasing cell membrane fluidity, promoting serotonin receptor accessibility.

The Endocrine Society classifies “sufficiency” as 30 nanograms per milliliter (ng/ml) or higher (40 to 60 ng/ml is “optimal”); “insufficiency” as 21 to 29 ng/ml; and “deficiency” as less than 20 ng/ml. Based on these classifications, approximately 70 percent of people living in the United States have vitamin D insufficiency and 40 percent have deficiency. In addition, dietary intake of marine omega-3 fatty acids is low. Robust evidence suggests that poor vitamin D status and suboptimal intake of omega-3s contribute to serotonin pathway dysfunction, ultimately contributing to the pathophysiology of neurobehavioral and neuropsychiatric disorders.

The authors of the present study conducted a randomized, double blind, placebo-controlled clinical trial involving 66 children (6 to 12 years of age) who had been diagnosed with ADHD. Half of the children received both 50,000 IU of vitamin D weekly plus 6 milligrams per kilogram of body weight per day of magnesium for eight weeks. The other half of the children received a placebo. The children’s parents completed questionnaires regarding the children’s mental health before and after the intervention.

At the end of the eight-week period, serum vitamin D and magnesium concentrations were markedly increased in the children who received the supplemental vitamin D and magnesium, compared to those who received the placebo. In addition, the children who received the supplemental vitamin D and magnesium exhibited fewer emotional, behavioral, and social problems, compared with the children who received the placebo.

These findings suggest that co-supplementation with vitamin D and magnesium improves behavior and mental health among children with ADHD. This was a small study, however, so further well-designed studies with larger sample sizes are needed to confirm these effects.

• Link to full publication.

• Learn more about the connection between vitamin D, omega-3 fatty acids, and neuropsychiatric disorders in this article co-authored by Dr. Rhonda Patrick.

• Learn more about vitamin D in our overview article.