The Neuro-transmitter enhancers caffeine and tyrosine are No 4 of the top 12 Metabolic Precision Gold Standard Supplements. That means they're highly recommended as they possess a substantial amount of data that suggests beneficial effects.

What are they?

Caffeine is a crystalline alkaloid, a member of the xanthine family of compounds found naturally in tea and coffee plants which acts as a mild stimulant of the central nervous system.

In the brain, a higher dopamine to serotonin ratio produce a sense of mental alertness, sharpness, well being and enhance performance. L-tyrosine is an amino acid that required for the synthesis of neurotransmitters such as dopamine, norepinephrine and epinephrine.

What do they do?

Caffeine affects stimulatory receptors in the central nervous system (CNS). Specifically, the inhibition of the adenosine A2A receptors, in the brain. At concentrations equivalent to a few cups of coffee a day, caffeine binds and blocks nerve cells that normally inhibit voluntary movements in the brain's movement centre, (the striatum). This creates that subtle "wired"� feeling from a jolt of caffeine. In research caffeine is shown to enhance athletic performance, promote fat metabolism, provide anti-cancer benefits and reduce the risk of type-2 diabetes.

An increased concentration of serotonin to dopamine in the brain during exercise has been implicated as an important factor in the onset of CNS fatigue. L-tyrosine administration increases dopamine synthesis and brain concentrations. Supplementing with this amino acid can reverse this ratio of serotonin to dopamine to boost workout intensity and delay fatigue.

Best to take when?

Caffeine is best used prior to exercise to enhance alertness and delay fatigue. In habitual users the stimulatory response per dose can diminish with frequency however caffeine's ability to metabolize fat may not necessarily be impaired by frequent consumption.

How much?

A research based recommendation is a 2-3 gram dose of L-tyrosine with water just before exercise. This will ensure an effective amount of tyrosine gets into circulation at the right time to delay or even prevent the serotonin to dopamine increase caused during exercise.

A dose of 5 mg caffeine per kg of body weight generally ensures a performance-enhancing effect in both endurance and short-duration, high intensity exercise. For a 70kg individual that equates to a hefty 350 milligrams. Be warned, anyone not use to caffeine will really feel the effects of this dose.

Remember, you don't need to start with this dose to experience a performance-enhancing effect. If you are new or sensitive to caffeine - scale it down to 2-3 mg per body weight per dose. Understand that caffeine is a safe, effective supplement for msot people to take. However, if you do have a history of poor cardiovasular health or even if you you're unsure in any way - its always best to check with your physician.
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