Low-dose lithium refers to supplemental lithium at doses of approximately 1–20 milligrams per day — several orders of magnitude below the therapeutic doses of 150–1,800mg/day used in psychiatric treatment of bipolar disorder. The distinction is critical and non-trivial: at psychiatric doses, lithium requires regular blood monitoring because it has a narrow therapeutic window and can cause serious toxicity; at nutritional or low supplemental doses, it behaves as a micronutrient with a broad safety margin and a pharmacological profile that is overlapping but distinct.
The rationale for low-dose lithium is primarily neuroprotective. Lithium inhibits glycogen synthase kinase-3 (GSK-3β), an enzyme that regulates dozens of cellular processes and is implicated in tau phosphorylation (Alzheimer's pathology), apoptosis, and inhibition of neurogenesis. GSK-3β inhibition promotes hippocampal neurogenesis, reduces amyloid-beta production, prevents tau hyperphosphorylation, and upregulates anti-apoptotic proteins (Bcl-2). At low doses, these effects may be achievable without the toxicity profile that accompanies sustained psychiatric-range dosing.
The epidemiological evidence is suggestive and unusual: multiple population studies across different countries have found inverse correlations between naturally occurring lithium levels in drinking water and rates of suicide, homicide, all-cause dementia, and violent crime — associations that have held up across replications in Texas, Japan, Austria, Greece, and elsewhere. A Japanese study (Terao et al., 2010) remains one of the most cited, showing a statistically significant negative correlation between drinking water lithium and suicide rates across 18 municipalities. These associations do not prove causation, but they have catalyzed serious research into low-dose lithium as a public health intervention and have generated an active clinical trial program.
Low-dose lithium is available as lithium orotate or lithium aspartate — organic lithium salts in which the lithium is bound to an organic acid carrier. These forms are not FDA-approved pharmaceutical drugs and are sold as dietary supplements. The elemental lithium content per 5mg "lithium orotate" tablet is approximately 1mg of elemental lithium.