Investigators compared supplementation with a 1-month course of vitamin B6 or B12 to supplementation with placebo in almost 500 adults. Results showed that vitamin B6 supplementation was associated with reductions in self-reported anxiety and a trend toward decreased depressive symptoms.
In addition, the vitamin B6 group showed increased levels of gamma-aminobutyric acid (GABA), as indicated by results on a visual test that was administered at the end of the trial. The test results demonstrated subtle changes in participants’ visual performance. The researchers considered this to be consistent with controlled levels of GABA-related brain activity.
Dr. David Field
However, “before practicing clinicians would recommend taking high doses of vitamin B6, a full-scale clinical trial would have to be carried out to verify the findings, assess any side effects, and find out which types of patients do or don’t benefit,” study investigator David Field, PhD, associate professor, School of Psychological and Clinical Language Sciences, University of Reading (England), told this news organization.
“My relatively small study can only be considered as an initial proof of concept,” Dr. Field said.
The findings were published online in the Journal of Human Psychopharmacology: Clinical and Experimental.
Eat Marmite?
“Recent research has connected mood disorders and some other neuropsychiatric conditions with disturbance in this balance, often in the direction of raised levels of brain activity,” Dr. Field noted.
Vitamin B6 is a coenzyme in the synthesis of GABA, an inhibitory neurotransmitter, from glutamate. Some previous research has suggested that vitamins B6 and B12 have a role in improving mood-related outcomes.
Dr. Field had reviewed a 2017 study of the effects on visual processing of eating Marmite, a type of food spread rich in vitamin B, every day for a few weeks.
“Remarkably, the results of that study suggested that eating Marmite had increased the level of the inhibitory neurotransmitter GABA in the visual part of the brain, damping down the level of neural activity slightly,” he said.
However, Marmite contains other B vitamins and other ingredients that might potentially account for this result, “plus, a lot of people don’t like the taste of Marmite,” Dr. Field noted.
Therefore, he wanted to “find out which individual ingredients were driving the effect, and B6 and B12 were the most plausible candidates.”
He decided to test these vitamins individually and to compare them to placebo. “I added the measures of anxiety and depression that were not in the Marmite study because I reasoned that if GABA levels were altered, this could improve those disorders, because we know that decreased levels of GABA in the brain occur in both of those conditions,” Dr. Field added.
Over the course of 5 years, investigators recruited 478 participants aged 18-58 years (mean age, 23 years; 381 women). Of these, 265 reported having anxiety, and 146 reported having depression.
The study participants were randomly assigned to receive either vitamin B6 (100 mg pyroxidine hydrochloride), vitamin B12 (1,000 mg methylcobalmin), or placebo tablets once daily for a month.
They also completed the Screen for Adult Anxiety Related Disorders (SCAARED) and the Mood and Feelings Questionnaire (MFQ) long version at baseline and following supplementation (“post test”), and they underwent three sensory tests that acted as assays of inhibitory function at post test.
In addition, 307 participants completed the Visual Contrast Sensitivity and Surround Suppression, which “measures the minimum percentage contrast between the lighter and darker regions of a striped pattern that can be detected (called the contrast threshold),” the investigators note.
The contrast threshold was measured with and without a suppressive surround mask that increases the threshold – an effect mediated by GABAergic connections in the visual cortex.
Participants (n = 172) also completed the Binocular Rivalry test and the Tactile Test Battery (n = 180). Both tests are designed to measure responses requiring GABAergic inhibitory activity.