Lithium is a naturally occurring alkali metal, found in trace amounts across the Earth’s crust, including in rocks, soil, and water. This element is present in all human organs and tissues, absorbed from the intestinal tract and excreted primarily by the kidneys. An essential nutrient is defined as a substance required for normal physiological function that the body cannot synthesize and must obtain from the diet. While lithium is universally present, its official classification as a required nutrient for human health is yet to be fully established.
Defining Essentiality
Official classification as an essential nutrient requires strong evidence that the substance has a specific biological role and a predictable deficiency syndrome occurs when intake is insufficient. Major human nutrition organizations, such as the Food and Nutrition Board of the National Academy of Medicine, have not formally listed lithium on their nutrient recommendation tables. Therefore, lithium is not currently recognized as an essential mineral alongside calcium, iron, or zinc.
The scientific debate persists because lithium appears to meet many criteria defining a micronutrient. Studies on animals, including rats and goats, demonstrated that a lithium-deficient diet could lead to reproductive problems, lowered immune status, and decreased longevity. Although defined human deficiency diseases have not been characterized, these animal models suggest a biological requirement.
Some scientists propose that the available experimental evidence is sufficient to accept lithium as an essential trace element. They have suggested a provisional Recommended Dietary Allowance (RDA) of around 1,000 micrograms (\(\mu\)g) per day for a 70-kilogram adult.
Biological Function in Trace Amounts
The biological activity of lithium at trace levels, far below therapeutic concentrations, centers largely on neuroprotection and mood modulation. Low, nutritional doses influence brain chemistry by affecting enzymes and neurotransmitter pathways involved in mental well-being and cellular resilience. Lithium enhances the activity of brain-derived neurotrophic factor (BDNF), a protein that supports the growth, function, and repair of neurons.
A primary mechanism involves the inhibition of the enzyme glycogen synthase kinase-3 beta (GSK-3 \(\beta\)). This enzyme is implicated in various neurological processes, and its overactivity is associated with conditions like Alzheimer’s disease. By modulating GSK-3 \(\beta\), trace lithium may play a role in reducing inflammation and protecting against cellular damage in the brain.
Trace levels also influence the balance of key neurotransmitters, including serotonin and dopamine, which are critical for mood regulation and impulse control. Epidemiological studies show an inverse association between the natural concentration of lithium in local drinking water supplies and the rates of suicide, aggression, and violent crime. These correlations suggest that trace lithium plays a meaningful role in supporting emotional stability and mental health, contributing to overall cellular health.
Trace Intake and Dietary Sources
Humans acquire trace lithium primarily through water and plant-based foods, which absorb the element from the soil. The concentration of lithium in these sources is highly variable, depending heavily on local geology and soil composition. This geological variability leads to wide differences in the average daily intake across different populations globally.
In the United States, the typical daily dietary intake of elemental lithium is estimated to range between 650 and 3,100 micrograms (\(\mu\)g). Grains and vegetables are the major contributors to this intake, providing an estimated 66% to more than 90% of the total amount. Richer sources include:
- Nuts
- Seeds
- Legumes
- Leafy greens
- Tomatoes
Drinking water is another significant source, though its contribution varies dramatically by location. Regions with lithium-rich ground water can have concentrations exceeding 1,000 micrograms per liter (\(\mu\)g/L). People living in these high-lithium areas naturally consume much higher amounts without evidence of adverse effects. However, intake may be significantly reduced for those who drink filtered or bottled water.
The Difference Between Trace Element and Therapeutic Drug
The most significant point of public confusion is the vast difference between the minute, environmentally acquired trace element and the powerful pharmacological agent. Therapeutic lithium salts, such as lithium carbonate, are mainstay psychiatric medications used primarily to stabilize mood in individuals with bipolar disorder and acute mania. These are administered at very high doses, measured in hundreds of milligrams (mg) per day.
A typical therapeutic dose for mood stabilization ranges from 600 to 1,800 milligrams of lithium salt daily. This dose is a thousand-fold greater than the daily intake from food and water, which is measured in micrograms (\(\mu\)g). The mechanism of action at these high concentrations involves complex effects on neural activity and second messenger systems.
The difference in dosage relates directly to safety and monitoring. Therapeutic lithium has a narrow therapeutic window, meaning the concentration required for effectiveness is close to the concentration that can cause toxicity. Patients on this medication require regular blood tests to maintain safe serum levels, typically between 0.6 and 1.2 milliequivalents per liter (mEq/L). In contrast, the trace amounts found in food and water are considered entirely safe and do not require medical monitoring. The debate over lithium’s essentiality as a trace element is distinct from its role as a powerful pharmaceutical agent.