Comment Re:There should be an easy natural observation (Score 1) 23
There have been quite a few studies that do just that. Well, not "taking lithium", as in the medication, because typical psychiatric doses of lithium (hundreds of milligrams per day) are like 2-3 orders of magnitude higher than typical dietary doses. But dietary doses themselves vary by orders of magnitude (some European studies put consumption in some places in Europe as low as a couple micrograms per day, while in places in northern Chile some people consume ~10mg per day), because lithium is so widely varied from place to place. One study found for example that one Slovakian bottled water product had 10 milligrams per litre, while the mean European bottled water had less than a microgram per litre. In most places, peoples' dietary consumption is closer to the lower end than the upper end. And the studies strongly suggest that people who naturally consume the higher amounts of lithium have lower rates dementia (there's also positive, though weaker, evidence for lower rates of violent crime and suicide). In general, it seems to be neuroprotective.
It's been argued that we should probably be lithiating water, e.g. that there should be minimum and maximum standards for lithium in drinking water the same way that there are minimums and maximums for numerous other minerals, with a provisional recommended daily intake of 1mg per day based on the evidence. But given the huge backlash to fluoride in water, I can't even imagine how harsh the backlash to lithium would be, given that people associate it with being a psychiatric medication (even though that's at doses orders of magnitude higher). It's just not going to happen.
I personally take 1mg of lithium a day. Which is well within the normal dietary range (in some places in northern Chile people naturally consume ~10mg per day!). A common supplement form is lithium orotate, but it's a weird choice - it's chosen because it's covalently bonded into a molecule which is delivered into cells whole, to "make it more effective", but A) that's not how normal dietary lithium is delivered, and B) orotic acid isn't exactly healthy. Instead, I make my own (both concentrate and diluted solution). I start with lithium carbonate, and while it's not available in food grade (anywhere I've found), it's a very common compound available at high purity (>99,5%), with easy composition tests - crimson flame test, density tests (offset by a typically poor packing density), low solubility in water but high bubbling solubility in weak acids (with no precipitate), etc). Because it's poorly soluble & tastes like baking soda / mineral water, I also add citric acid to the solution, forming lithium citrate. Even if the impurities were pure lead, the amount would still be small when you're only taking 1mg a day. But actual impurities are mostly (A) water, (B) other lithium compounds (hydroxide, chloride, sulfate, etc etc), and (C) other similar mono- and divalent cations to lithium, such as sodium, potassium, calcium, magnesium, plus some iron, alumium and silicon due to their ubiquity in nature and presence in processing.