Anxiety disorders are estimated to affect about 40 million adults in the United States. While highly treatable by a number of psychological and psychiatric therapies, it has long been the subject of clinical studies that nutritional intervention might be able to yield benefits to anxiety and other mood disorders. While intensive research has been carried out on potential biomarkers, any direct cause of anxiety from genetic, neuroimaging, blood testing, and neurochemical perspectives has not been substantiated.
 
In a review published this month in Recent Advances in Nutritional Psychiatry, a group of researchers evaluated evidence which suggests that the ketogenic diet might be a worthwhile anxiolytic approach in future research.
 
“We will focus on the biological aspect of the mechanism of ketosis,” the authors wrote. “The direct and indirect influence on the central nervous system of [ketogenic dieting] can be observed in the increasing of the cerebral blood flow, and the decreasing of the mammalian target of rapamycin, by the increase of the level of endothelial nitric oxide synthase protein expression, but also passively. The indirect, ‘passive’ effects on the central nervous system are supposed to be mediated by microbiota through an increase of short-chain fatty acids and a decrease of GABA. Bacteria such as Akkermansia muciniphila and Lactobacillus are known as short-chain fatty acid producers.”
 
Ketogenic dieting also has appetite-stimulating properties, the authors said, increasing the brain’s GABA concentrations of AMP, and decreasing reactive oxygen species.
 
Gut Microbiota Establish the Link
The authors of the review discussed several potential pathways by which nutrition may effect anxiety outcomes through the interplay that exists between neurotransmitter production in the gut, and psychological outcomes.
 
A majority of serotonin produced by the body is synthesized in the gut. It is believed that gut defects in the transmission of serotonin and nonadrenal neurotransmitters could be impacted by a low-carbohydrate, high fat (LCHF) diet. The anti-inflammatory properties of such a diet may also reduce inflammation, the synthesis of cortisol, and reactive oxygen species, the researchers said, which could be linked to some anxiolytic benefit.
 
The effects of the ketogenic diet may also be beneficial by mitigating the production of excess glutamate, while also attenuating any potential GABA deficiencies linked to gut microbiota, the researchers said.
 
The ‘clean keto’ version of this diet is most likely to have beneficial effects on inducing anxiolytic changes to gut microbiota, the authors said. The most benefit is likely to be seen if macronutrients come from low-processed food sources which are also rich in micronutrients.
 
“A study on over 121,000 participants concluded that high stress and high neuroticism levels were associated with poorer diet quality, however, poor diet quality did not predict emotional or mental health problems. Although the data suggest that enhancing diet quality may not hold promise in preventing mental disorders, patients may benefit from a specific type of nutrition regiment to enhance the GABAergic transmission and support the gut-brain axis,” the authors said.
 
“Although there is a growing body of literature that links nutrition to mood, little can be found on the proposed biological mechanisms of action of certain micro- and macronutrients on neurotransmission, leaving studies with, mainly, epidemiological data,” the authors concluded. “There is also evidence with regard to the gut-brain axis, in which some species of bacteria have the ability to generate the neuroendocrine hormones and/or neuroactive compounds involved in a key aspect of neurotransmission, which may be responsible for the anxiolytic effect.”
 
“The findings rationalize the need for more detailed, longitudinal research on the ways in which diet and microbiome interactions may be better understood and managed in order to optimize the reduction of anxiety for the benefit of the patients […] in our mind, the LCHF diet is a promising, well-accepted diet regimen which has an impact on anxiety disorders, supporting mainly long-term relapse prevention strategies, in combination with the already-approved strategies.”