Synergy in Common Choline and Racetam Stacks
One of the difficulties most nootropic enthusiasts have upon building their latest stack is picking a choline source. There are good arguments for many choline forms, but I think that, ultimately, it comes down to a matter of priority and stack synergy. I’ve picked what I consider the big three (choline bitartrate, CDP choline, and Alpha GPC) and have shown what the benefits are for each.
This should be an appealing choice for anyone who does not have the extra cash to pick up CDP-choline or Alpha GPC. That really appears to be its “synergistic” function. Going with bitartrate might allow you to afford another ingredient for your stack or even just afford your basic racetam/choline supplement combination if money is tight.
Choline bitartrate is the cheapest choline supplement, but it’s also the least bioavailable. Unlike, CDP Choline and alpha-GPC, the bitartrate form doesn’t easily cross the blood-brain barrier.
Bitartrate is a precursor to acetylcholine. This choline source is about 40% choline by weight. However, due to its limited bioavailability, the amount of acetylcholine this helps create is far less.
Despite its reduced potency, the bitartrate form of choline is still sufficient for liver benefits of choline. But due to its limitation in passing the blood-brain barrier, this form of choline has limited nootropic properties and lacked evidence in boosting memory in healthy adults (source).
CDP choline can be considered a nootropic on its own given the evidence that it increases dopamine and acetylcholine receptor density, improves memory, and provides mental energy. Also, CDP choline breaks down in the body into choline and uridine.  If you are taking DHA as part of your stack, this will help create phosphotidylcholine.  Since CDP choline readily crosses the blood-brain barrier, there is little concern for waste.
According to studies, this is the best choline format for combating memory-related issues due to aging. It’s also effective in boosting memory in young adults. Other non-nootropic uses include being used as an anti-addictive supplement against cocaine.
If you’re looking to boost memory or use in your uridine, or Mr Happy, stack then this is the optimal choline supplement. If you’re not familiar with this stack, see the original longecity.org thread or the experiential post on reddit.com.
Alpha GPC is another choline source with its own nootropic effects with or without a racetam through its ability to improve memory, focus, and concentration.  Alpha GPC is shown to also use DHA to help promote nerve growth.  Alpha GPC powder is usually the most expensive of the three forms shown.
Despite being the most expensive, this choline format is the most efficient source of choline and easily passes the blood-brain barrier due to its phospholipid properties.
In order for the body to use alpha-GPC it normally converts phosphatidylcholine stores in the brain. Phosphatidylcholine is used for the production of cell membranes. Dietary sources of alpha-GPC are scarce, which makes supplementing with this version almost necessary if you want to preserve your body’s phosphatidylcholine stores
Notes on stacks:
If your stack has Lion’s Mane or noopept (both increase nerve growth factor), Alpha GPC powder might not be the way to go. Through a simple racetam/CDP choline/DHA/noopept stack, it seems that the synergistic functions of the four compounds would benefit each other the most. Maybe add some creatine and sulbutiamine, and you’ve got yourself a perfect brain booster and wallet lightener.
- Kidd, Parris M. “Neurodegeneration From Mitochondrial Insufficiency: Nutrients, Stem Cells, Growth Factors, And Prospects For Brain Rebuilding Using Integrative Management.” Alternative Medicine Review10.4 (2005): 268-293. Academic Search Elite. Web. 8 Sept. 2012.