L-Theanine

Gomez-Ramirez, et al. The deployment of intersensory selective attention: a high-density electrical mapping study of the effects of theanine.

https://www.ncbi.nlm.nih.gov/pubmed/17272967

Kelly, et al. L-Theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance.

https://www.ncbi.nlm.nih.gov/pubmed/18641209

Kimura, et al. L-Theanine reduces psychological and physiological stress responses.

https://www.ncbi.nlm.nih.gov/pubmed/16930802

Nobre, et al. L-Theanine, a natural constituent in tea, and its effect on mental state.

https://www.ncbi.nlm.nih.gov/pubmed/18296328

Guarana

Arantes, et al. Mechanisms involved in anti-aging effects of guarana in caenorhabditis elegans.

http://dx.doi.org/10.1590/1414-431x20187552

Kennedy, et al. Improved cognitive performance in human volunteers following administration of guarana extract.

https://doi.org/10.1016/j.pbb.2004.07.014

Moustakas, et al. Guarana provides additional stimulation over caffeine alone in the planarian model.

https://doi.org/10.1371/journal.pone.0123310

Choline

Zeisel. Choline: an important nutrient in brain development, liver function and carcinogenesis.

https://doi.org/10.1080/07315724.1992.10718251

Zeisel, et al. Nutritional importance of choline for brain development.

https://doi.org/10.1080/07315724.2004.10719433

Ginkgo Biloba

Ahlemeyer & Krieglstein. Neuroprotective effects of Ginkgo biloba extract.

https://doi.org/10.1007/s00018-003-3080-1

Ponto & Schultz. Ginkgo biloba extract review on CNS effects.

https://pubmed.ncbi.nlm.nih.gov/12938868/

Rapin, et al. Demonstration of the "anti-stress" activity of an extract of Ginkgo biloba using a discrimination learning task.

https://doi.org/10.1016/0306-3623(94)90111-2

van Beek. Chemical analysis of Ginkgo biloba leaves and extracts.

https://doi.org/10.1016/S0021-9673(02)00172-3

L-Tyrosine

Banderet & Lieberman. Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans.

https://doi.org/10.1016/0361-9230(89)90096-8

Colzato, et al. Working memory reloaded: tyrosine repletes updating in the N-back task.

https://doi.org/10.3389/fnbeh.2013.00200

Neri, et al. The effects of tyrosine on cognitive performance during extended wakefulness.

https://www.ncbi.nlm.nih.gov/pubmed/7794222

Thomas, et al. Tyrosine improves working memory in a multitasking environment.

https://doi.org/10.1016/S0091-3057(99)00094-5

Panax Ginseng

Reay et al. Effects of Panax ginseng, consumed with and without glucose, on blood glucose levels and cognitive performance during sustained ‘mentally demanding’ tasks.

https://doi.org/10.1177%2F0269881106061516

Acetyl L-Carnitine

Smeland et al. Chronic acetyl-L-carnitine alters brain energy metabolism and increases noradrenaline and serotonin content in healthy mice.

https://doi.org/10.1016/j.neuint.2012.04.008

L. Acidophilus

Carabetti, et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/

Cerdó et al. Probiotic, Prebiotic, and Brain Development.

https://doi.org/10.3390/nu9111247

Wang, et al. Effect of Probiotics on Central Nervous System Functions in Animals and Humans: A Systematic Review.

https://doi.org/10.5056/jnm16018

Curcumin

Seddon et al. Effects of Curcumin on Cognitive Function - A Systematic Review of Randomized Controlled Trials.

https://www.xiahepublishing.com/2472-0712/ArticleFullText.aspx?sid=2&id=10.14218%2fERHM.2018.00024

Xu, et al. Curcumin reverses impaired cognition and neuronal plasticity induced by chronic stress.

https://www.sciencedirect.com/science/article/pii/S0028390809001634

Zhu, et al. Curcumin intervention for cognitive function in different types of people: A systematic review and meta‐analysis.

https://onlinelibrary.wiley.com/doi/full/10.1002/ptr.6257