What biological roles does it play?
There is evidence to suggest that lithium is also an essential plant element (Macrae et al. 1993)
"Lithium - Still interesting after all these years."
studies performed on populations living in areas with low Li levels in water supplies have been associated with higher rates of suicides, homicides, and the arrest rate for drug abuse and other crimes. Li appears to play a significant role in early fetal development as evidenced by high Li levels during the early ges-tational period. Biochemically, the mechanism of Li action involves multifactor and interconnected pathways with enzymes, hormones, vitamins, and growth and transforming factors. This body of evidence now appears sufficient to label Li as an essential element with the recommended RDA for a 70 kg adult of 1,000 mg/day.
Using data for 27 Texas counties from 1978–1987, it is shown that the incidence rates of suicide, homicide, and rape are significantly higher in counties whose drinking water supplies contain little or no lithium than in counties with water lithium levels ranging from 70–170 μg/L; the differences remain statistically significant (p<0.01) after corrections for population density.
The corresponding associations with the incidence rates of robbery, burglary, and theft were statistically significant withp<0.05. These results suggest that lithium has moderating effects on suicidal and violent criminal behavior at levels that may be encountered in municipal water supplies.
Comparisons of drinking water lithium levels, in the respective Texas counties, with the incidences of arrests for possession of opium, cocaine, and their derivatives (morphine, heroin, and codeine) from 1981–1986 also produced statistically significant inverse associations, whereas no significant or consistent associations were observed with the reported arrest rates for possession of marijuana, driving under the influence of alcohol, and drunkenness.
These results suggest that lithium at low dosage levels has a generally beneficial effect on human behavior, which may be associated with the functions of lithium as a nutritionally-essential trace element. Subject to confirmation by controlled experiments with high-risk populations, increasing the human lithium intakes by supplementation, or the lithiation of drinking water is suggested as a possible means of crime, suicide, and drug-dependency reduction at the individual and community level.
Zarse K., Terao T., Tian J., Iwata N., Ishii N., Ristow M.
Low-dose lithium uptake promotes longevity in humans and metazoans.
European Journal of Nutrition. 50 (5) (pp 387-389), 2011
. Because of lithium's stabilizing effect on glutamate receptors, scientists are also studying whether this medication can protect from the cell death that occurs in conditions such as Parkinson's, Huntington's and Alzheimer's.
Lithium is found in trace amounts in all soils primarily in the clay fraction, and to a lesser extent in the organic soil fraction , in amounts ranging from 7 to 200 μg/g [9,10]. It is present in surface water at levels between 1 and 10 μg/L, in sea water at 0.18 μg/L [9,10]. The lithium concentrations in ground water may reach 500 μg/L, in river water of lithium-rich regions of northern Chile, 1508 and 5170 μg/L, respectively . In the latter regions, total Li intakes may reach 10 mg/day, without evidence of adverse effects to the local population. Still higher lithium levels, up to 100 mg/L are found in some natural mineral waters [1,12].
Lithium is taken up by all plants, although it appears not to be required for their growth and development. However, this question is not yet completely resolved, since, in the ppb range, stimulatory effects of lithium on plant growth have been observed .