Free form amino acids are individual amino acids not bound in peptide chains and are directly absorbed into the bloodstream without the need for digestion. Their use to support the brain-body system is based on the scientific understanding that certain amino acids are precursors to neurotransmitters—the chemical messengers of the brain. For example, tryptophan is a precursor to serotonin, tyrosine to dopamine and norepinephrine, and glutamine to glutamate and GABA. Supplementation with free form amino acids can, in some cases, increase the availability of these neurotransmitters, potentially supporting cognitive function, mood, and stress response.

Several studies have examined specific amino acids for their effects on mood and cognitive performance. For instance, tryptophan supplementation has been shown to influence mood and decrease symptoms of depression in some individuals, though effects are generally modest. Tyrosine has some evidence suggesting it may support cognitive performance under stress or fatigue. However, most of the evidence is limited to specific amino acids rather than broad "free form amino acids" blends, and the effects are often context-dependent. There is less evidence that general supplementation with free form amino acids offers broad brain-body system benefits in healthy individuals.

In summary, there is scientific rationale and moderate evidence for the use of specific free form amino acids to support certain aspects of brain function, but evidence does not support blanket claims for all free form amino acids or general brain-body system support in all populations.