What is Kynurenic Acid: A Nutrient or Toxin?

Research is confirming the biochemical called kynurenic acid is necessary for many metabolic processes. But increased levels are linked with mental disorders and other conditions. So is it a nutrient or a toxin?

The science of kynurenic acid

Research has connected increased kynurenic acid levels with cancer, schizophrenia, inflammatory bowel syndrome and a number of other conditions.

Yet at the same time, it has been linked to healthy conditions and decreased infections, notably digestive conditions. While higher levels are linked with inflammatory bowel syndrome, lower levels are linked to irritable bowel syndrome.

Other research has linked it to reductions in ulcers, colitis, and other gut-related conditions.

And its presence is considered necessary in order to stimulate cognition. It is used within our central nervous system to act as a go-between with dopamine. In fact, research has pointed to the reality that this biochemical is the key component of dopamine neuron firing, and when its levels are too high among the central nervous system, neuropathic and even disorienting conditions can prevail.

Increased levels of production of this biochemical in the oral cavity have been linked with mouth abscesses. But decreased levels have been linked with increased infections. What the heck is going on?

Is kynurenic acid a nutrient?

Yet even with this mix of evidence, some researchers have promoted the idea that kynurenic acid be considered a nutrient – something to be supplemented in order to provoke its benefits in disease prevention.

Supporting this notion is the finding that this biochemical has been found throughout healthy organs and tissues throughout the body – involving it in healthy metabolism. Kynurenic acid at different concentrations has been found in the brain, liver, lungs, intestines, muscles, bloodstream, spleen and of course the intestines.

Should we supplement with it?

Kynurenic acid has been found to bind to some of the body’s most important cell receptors, including nerve and brain cell GABA receptors, NMDA (N-methyl-D-aspartate receptor) receptors, AMPA receptors, nicotinic receptors, platelet-aggregation receptors, and many others.

One of the pieces of logic for the idea of supplementing this biochemical is the finding that it is a constituent of some of the healthiest medicinal plants. Kynurenic acid has been found in higher quantities among dandelion, nettles and other herbs known for their ability to reduce inflammation and help liver function.

Yet as the author has illustrated among other research, the isolation of phytonutrients from herbs has proven wrought with danger, as they can produce unintended side effects. This isolation of active constituents has been the misguided strategy of pharmaceutical companies over the decades – as some 40-60% of pharmaceuticals have been derived from plants and then synthesized.

One of the more confusing – and most important – issues is the fact that bacteria produce this acid. Kynurenic acid has been found produced by E. coli bacteria, as well from probiotic bacteria such as L. acidophilus, L. lactis and others.

Kynurenic acid and gut bacteria

Actually, some of the most revealing research on kynurenic acid has taken place among bacteria research. Many bacteria – including our probiotics – actually produce kynurenic acid. And certain concentrations of it promote or reduce their growth.

A study from Poland’s Maria Curie-Skłodowska University found that kynurenic acid at specific concentrations promoted the growth of probiotic bacteria such as Lactobacillus acidophilus, L. rhamnosus, and different Bifidobacterium species. At the same time, kynurenic acid at the same concentrations repelled L. reuteri, L. rhamnosus GG, L. plantarum, L. delbrueckii and B. lactis.

Even within certain species of L. acidophilus and others, the researchers found that certain concentrations promoted growth among some and repelled growth among others.

This and other research has led to the postulation that bacteria utilize kynurenic acid to adjust their environment to their liking, and to the liking of those species they work well with. And those species that don’t work well together will maintain different levels of kynurenic acid in order to maintain their colonies.

This tendency of regulating their environments using this biochemical is also seen in the production of another acid – lactic acid – which certain species of bacteria – notably lactic acid producing species (hence the name “lactobacillus”) – use to regulate their environment and irritate their competitors.

We might thus compare this colony-regulating process similar to how an audience will cheer on their team and boo their opponent’s team. But instead of sound, these smart bacteria utilize the concentration of acids.

And this ability to regulate kynurenic acid levels within the gut – and thus within the rest of the body – ties in directly to how our gut bacteria influence our mental health as well as our metabolism and disease proclivities.

While kynurenic acid isn’t the only tool that bacteria utilize to regulate our body’s metabolism, it is certainly one of the complex facilities that these smart creatures use to help regulate our entire physiology.

REFERENCES:

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Erhardt S, Schwieler L, Nilsson L, Linderholm K, Engberg G. The kynurenic acid hypothesis of schizophrenia. Physiol Behav. 2007 Sep 10;92(1-2):203-9.

Kuc D, Rahnama M, Tomaszewski T, Rzeski W, Wejksza K, Urbanik-Sypniewska T, Parada-Turska J, Wielosz M, Turski WA. Kynurenic acid in human saliva–does it influence oral microflora? Pharmacol Rep. 2006 May-Jun;58(3):393-8.

Dolecka J, Urbanik-Sypniewska T, Skrzydło-Radomańska B, Parada-Turska J. Effect of kynurenic acid on the viability of probiotics in vitro. Pharmacol Rep. 2011;63(2):548-51.

Turski MP, Turska M, Zgrajka W, Bartnik M, Kocki T, Turski WA. Distribution, synthesis, and absorption of kynurenic acid in plants. Planta Med. 2011 May;77(8):858-64. doi: 10.1055/s-0030-1250604.