There is a collection of important updates this time around, consisting of three popular nootropic compounds paired with a soon-to-be-popular vitamin and then an understudied herb.
To get the uneventful stuff out of the way, Fadogia agrestis has been added to the Testosterone Booster list of supplements. This is an herb with a lone study in rats to support an increase in testosterone, and while it does seem a bit more potent than most other herbs (excluding bulbine natalensis) it is still very preliminary.
Both CDP-choline and Alpha-GPC are phospholipids that contain choline, and each supplement can be seen as a prodrug for two different things (CDP-choline gives the body choline and uridine, while Alpha-GPC gives the body choline and glycerophosphate). Both of these compounds can increase brain acetylcholine levels, and due to the other components supporting membrane dynamics they may also exert neuroprotective effects.
They are better cholinergics than basic choline supplementation or lecithin for the purposes of cognitive enhancement, and while they are both proven to aid in memory formation in older individuals with memory decline, there is mixed evidence in otherwise healthy youth (it would be wrong to say they are ineffective, but it is less reliable for a completely healthy person).
Vinpocetine is an alkaloid that is said to be neuroprotective. While it has a wide variety of possible mechanisms, practically speaking, two of them (GABAB receptor ligand and sodium channel blocker) seem to be most relevant.
There is insufficient evidence to support vinpocetine as a cognitive enhancer, although it does appear to be neuroprotective and specifically potent against inflammatory stressors to the brain. Due to the increase in glucose metabolism seen with vinpocetine, it could potentially increase cognition although this is not demonstrated in youth yet.
Thankfully, however, the concerns associated with vinpocetine being antidopaminergic (with some sources saying that this 'reserpine-like action' is potentially dangerous) occur at a very high concentration and are likely not practically relevant for oral supplementation.
Both cholinergics (CDP-choline and Alpha-GPC) are potentially useful not only for providing choline to the brain, but for increasing phospholipid synthesis in the brain; due to these roles, both of these molecules have a role in promoting cognition and memory formation in elderly persons (pretty much established) and youth (possible, but less reliable). Vinpocetine is neuroprotective against a lack of oxygen and inflammation, but has not been shown to promote cognition in otherwise healthy use and its role as a nootropic is questionable.
Finally, Vitamin K has been added and is the major update this week. Vitamin K is quite important for a few reasons:
It is subject to the same problem as Vitamin D is, in the sense that while the RDA is at a level that is easy to hit (or to 'get 100% of your daily values'), the optimal intake is much higher, approximately 10-fold the RDA.
It would be pretty much impossible, excluding a large amount of matcha tea or natto, to acquire the optimal levels of vitamin K through the diet (that being said, if you are willing to consume 30g of matcha tea or 50g natto daily then that is sufficient).
The benefits associated with higher intakes are mostly centralized around reducing calcium buildup in arteries, which then reduces cardiovascular mortality risk and is also implicated in improving insulin sensitivity, reducing fracture rate and falls, and longevity. Due to the last two points being goals of vitamin D as well and how a possible side-effect of excessive vitamin D would be calcium buildup, vitamin K is seen as synergistic with vitamin D (on more than just bone health)
There are many other benefits associated with vitamin K supplementation, but currently only those related to calcium buildup in the arteries have actual trials with supplementation noting benefits. Other possible benefits, such as improving pancreatic function or being neuroprotective, are highly promising but their relevance to supplementation not yet proven.
Vitamin K, in a sense, is set up to be 'the next Vitamin D' pending more research. It falls subject to the same complications that vitamin D faces (and opens up a fairly unique role for supplementation) and has a similarly high safety threshold despite being a fat soluble vitamin.