Exploring the Benefits of Short Chain Fatty Acids on Autism and ADHD

Understanding Short Chain Fatty Acids (SCFAs)

Short Chain Fatty Acids (SCFAs) are a type of fatty acid that are produced when dietary fibers are fermented in the colon. They are primarily composed of acetate, propionate, and butyrate, and are known for their role in maintaining gut health. Recent studies have begun exploring their potential impact on neurological development and neuroinflammation, particularly in conditions like Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD).

The Gut-Brain Connection

The gut-brain axis refers to the bidirectional communication network between the central nervous system and the gastrointestinal tract 1. This complex relationship involves several pathways which impact neuroinflammation, metabolic signaling and neurotransmitter production.

Role of SCFAs in Mitigating Neuroinflammation

SCFAs modulate microglial function, the immune cells in the brain and their heightened awareness levels for attack. They can reduce pro-inflammatory cytokine secretion by glial cells

Role of SCFAs in Making new brain cells

Neurogenesis: SCFAs may contribute to increased neurogenesis in the brain. This was found to be the main mechanism also behind many psychiatric drugs like anti-depressants

Role of SCFAs in Neurotransmitter Production

Serotonin Biosynthesis: SCFAs support serotonin production in the brain, primarily though gut-brain interactions. Of which, SCFA can cross into the brain directly.
Neurotransmitter Regulation: SCFAs may influence the balance and synthesis of various neurotransmitters. Given altered levels in autism and in ADHD this is very important.

Dietary Sources of SCFAs

To boost SCFA production, it is important to consume a diet rich in dietary fibers. Some excellent sources include:

Whole grains such as oats and barley
Fruits like apples and bananas
Vegetables such as broccoli and carrots
Legumes including beans and lentils
Butter is a rich source for butyrate
In addition, it is preferable to have higher butyrate levels to keep propionic acids levels low. Propionic acid is found in the form of food additive, E280, in baked good that are meant to have a long shelf life such as cookies, cakes but also breads. 

A study published in PLOS ONE examined the effects of propionic acid (PPA) administration on rats, which showed autism-like behaviors including increased aggression [1]. Key findings include:

1. Behavioral Changes:

   - Enhanced aggressive behavior during social interactions was observed in rats treated with 500 mg/kg propionic acid compared to controls [1]. 

   - This increase in aggression was noticeable from day 14 after PPA administration [1].

2. Temporal Relationship:

   - The appearance of autism-like behaviors, including increased aggression, was observed after PPA administration [1].

   - Changes in gene expression in the hippocampus were detected between early and late post-induction days following PPA administration [1].

The regulatory limits in the EU are that propionic acid (E280) has maximum permitted levels for use in bread and rolls ranging from 1000 to 3000 mg/kg 4.

Future Directions for Research

As our understanding of the impact of SCFAs on neurodevelopmental disorders grows, it opens up new avenues for research and treatment. Future studies should focus on nutritional avenues for treating autism , ADD/ADHD and other developmental delays. 

Citations:

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7524304/

[2] https://www.sciencedirect.com/science/article/pii/S2666354624001078

[3] https://pmc.ncbi.nlm.nih.gov/articles/PMC7830868/

[4] https://www.psypost.org/new-study-links-early-gut-flora-disturbances-to-autism-and-adhd-development/

[5] https://psychiatryonline.org/doi/10.1176/appi.focus.24022008

[6] https://acamh.onlinelibrary.wiley.com/doi/10.1111/jcpp.13962

[7] https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1000419/full

[8] https://www.nature.com/articles/s41398-023-02729-3

[9] https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2024.1341656/full

[10] https://onlinelibrary.wiley.com/doi/10.1002/npr2.12437

[11] https://pubmed.ncbi.nlm.nih.gov/29447237/

[12] https://pubmed.ncbi.nlm.nih.gov/37640163/

[13] https://www.nature.com/articles/s41598-019-45348-z

[14] https://www.sciencedirect.com/science/article/abs/pii/S0161813X16300973

[15] https://www.researchgate.net/publication/323205813_Pathophysiological_and_neurobehavioral_characteristics_of_a_propionic_acid-mediated_autism-like_rat_model

[16] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192925

[17] https://www.sciencedirect.com/science/article/abs/pii/S0278584619302672

[18] https://www.mdpi.com/2072-6643/14/6/1280

[19] https://link.springer.com/10.1007/978-1-4614-4788-7_106

[20] https://www.researchgate.net/publication/352628131_Pathophysiological_and_neurobehavioral_characteristics_of_a_propionic_acid-mediated_autism-like_rat_model