Your current supplement stack includes a variety of well-known nootropics and vitamins that can potentially support cognitive function, providing benefits such as improved motivation, energy, focus, and memory. Below is a breakdown of your list and the potential effects based on the research:

1. Magnesium, B6, Zinc: This combination is often used to support overall brain health and neurotransmitter function¹. Magnesium is essential for nerve transmission and energy production, while B6 aids in neurotransmitter synthesis, and zinc can modulate synaptic function.

2. Alpha GPC: This choline supplement may enhance cognitive performance by boosting acetylcholine levels, a neurotransmitter associated with memory and learning².

3. NAC (N-Acetyl Cysteine): Known for its antioxidant properties, NAC may help reduce oxidative stress and support brain health, potentially improving cognitive function³.

4. Caffeine: Widely used for increasing alertness and focus, caffeine stimulates the central nervous system and can enhance cognitive performance, especially when combined with L-theanine⁴.

5. L-theanine: Often paired with caffeine, it can counteract the jitteriness some people experience from caffeine alone, promoting a state of relaxed alertness⁵.

6. L-tyrosine: This amino acid can improve cognitive flexibility and performance under stress, which supports motivation and focus⁶.

7. L-taurine: Though less researched for cognitive enhancement, taurine has been shown to support neurological health and is commonly included in energy supplements⁷.

8. Uridine: May support cognitive function by contributing to synapse formation and brain phospholipid synthesis⁸.

9. Vitamins A, D, E, K, C: These vitamins are essential for maintaining general health, including brain health. Vitamin C acts as an antioxidant, while Vitamins A, D, E, and K play roles in neurological function⁹.

For dosages, it's crucial to follow guidelines that are typically provided on the supplement labels or consult with a healthcare provider, especially considering factors like age, weight, and specific health conditions.

Regarding nicotine in your list, it's important to approach with caution due to its addictive nature and potential negative health impacts.

To enhance your stack further, consider:

• Omega-3 Fatty Acids: Known for supporting brain health and reducing inflammation¹⁰.
• Bacopa Monnieri: An herb used traditionally for cognitive enhancement and reducing anxiety¹¹.
• Rhodiola Rosea: An adaptogenic herb that can help improve fatigue and brain function under stress¹².

These suggestions are based on current research, but individual responses can vary, and consulting with a healthcare professional is recommended for tailored advice.