Originally written by ZRT Laboratory author. Reproduced with permission. Last reviewed: May 2026.
We are constantly exposed to elements — both nutritional and toxic — shaped by the environments we live and work in. These elements represent a fundamental yin and yang of health and disease: the right ones, in the right amounts, are essential for life; the wrong ones, or the right ones in excess, can quietly erode it.
With heavy metals, contamination is now so widespread that the question is no longer whether exposure has occurred, but how much — and for how long.
How Heavy Metals Affect the Brain
Toxicity from low-level heavy metal exposure can produce a wide array of neurological disturbances that are far more insidious than acute poisoning. While the effects may appear superficially mild at first, the body gradually distributes and stores heavy metals over time — a process known as bioaccumulation — and neurotoxic effects become increasingly inevitable.
One protein at a time, these toxic elements hijack brain proteins, displacing the minerals needed for proper neuronal function and replacing them with ones that permanently propagate oxidative stress — while simultaneously stripping the body of its natural defences. Chronic exposure to arsenic, bromine, cadmium, and mercury from industrial pollution can have grave consequences, masked by seemingly unrelated symptoms such as depression, anxiety, insomnia, headaches, memory problems, aggression, and developmental difficulties.
Exposure to even moderate contamination levels is implicated in cognitive and neurological deficits associated with poorer mental health — symptoms that can be extremely difficult to decipher without testing.
The Role of Nutrients in Brain Health
Diet is increasingly recognised as a modifiable factor intrinsically linked to human cognition, behaviour, and emotional wellbeing. Insufficient dietary intake of certain minerals has been associated with neurocognitive deficits, particularly in vulnerable populations such as children, whose nervous systems continue developing for many years [1].
Testing elements alongside neurotransmitters offers a powerful opportunity to confirm clinical suspicions and understand how micronutrient status — or toxic element exposure — is contributing to shifting mood balance. Below is a literature-based overview of key elements and their importance for nervous system health.
Key Elements and Their Impact on Mental Health
Iodine
As an essential component of the active thyroid hormone triiodothyronine (T3), iodine deficiency directly impairs thyroid hormone synthesis and compromises thyroid function throughout the body. Adequate thyroid function is critical for neurological development, and iodine's role in brain growth has long been established [2]. Children born to mothers in even moderately iodine-deficient areas are at increased risk of behavioural, psychoneurological, and intellectual difficulties [1][3].
If you're concerned about thyroid function alongside heavy metal exposure, our Thyroid, Heavy Metals & Essential Elements Test measures both in a single at-home kit.
Bromine
At high levels — typically through exposure to environmental pollutants such as brominated flame retardants — bromine induces neurotoxicity by inappropriately modifying glycine, glutamate, and GABA signalling. Excessive bromine also interferes with iodine uptake into the thyroid gland, preventing thyroid hormone synthesis. Neurological consequences of excessive bromine exposure include detrimental changes in cognition and mood [4].
Selenium
Anti-inflammatory and neuroprotective, selenium is an essential trace element that actively combats mercury and cadmium toxicity. It is vital for the proper functioning of selenoproteins involved in antioxidant defences in the brain, thyroid hormone activation, and glutathione production [5] — biochemical systems whose dysregulation is closely associated with neuropsychiatric conditions.
Research suggests there is an optimal selenium range in relation to depressive symptoms: both too little and too much selenium are linked with oxidative and inflammatory pathways, offering a mechanistic explanation for the relationship between selenium levels and depression [6].
Selenium also displays selective inhibition of monoamine oxidase A (MAO A), the enzyme that breaks down serotonin. This inhibitory effect can elevate serotonin levels — potentially beneficial for patients whose mood difficulties are rooted in serotonin deficiency [7]. In dopaminergic neurons, which are particularly vulnerable to oxidative stress, selenium plays a protective role and helps prevent neurodegeneration [8].
Arsenic
Arsenic disrupts serotonin and dopamine metabolism, compromising neuronal health even at low levels of exposure. It predisposes individuals to cognitive dysfunction and increased susceptibility to mood disorders. Additionally, arsenic can induce neuronal death by stimulating processes implicated in Alzheimer's disease [9][10][11].
Cadmium
Cadmium disrupts the delicate balance between glycine, glutamate, and GABA, negatively impacting memory and cognition — and is particularly destructive to white matter in the brain. Cadmium exposure has well-documented detrimental effects on neurocognitive development in children, and is associated with learning disabilities, lower IQ, attention deficits, behavioural problems, and hearing loss [10][12][13][14][15].
Mercury
Mercury is a potent neurotoxin that increases oxidative stress by permanently inhibiting glutathione function, stripping neurons of their defensive mechanisms. It radically skews neurotransmission — stimulating excitatory signalling (glutamate, dopamine) while suppressing inhibitory signalling (GABA). Mercury exposure can cause a range of neurological symptoms including irritability, mood swings, headaches, concentration and memory difficulties, and sleep disturbances [5][17][18].
To assess your exposure to mercury, cadmium, arsenic, and other heavy metals alongside essential minerals, our Heavy Metals & Mineral Balance Test uses ICP-MS analysis on dried blood spot and urine samples — the same technology used in specialist clinical laboratories.
Lithium
In trace amounts, lithium has been shown to improve mood and slow the progression of dementia. Its effects on the brain are neuroprotective, antioxidant, and regenerative. Lithium can modulate monoamine oxidase activity to appropriately regulate the breakdown of serotonin, dopamine, and phenethylamine [19][20].
Why Testing Elements and Neurotransmitters Together Matters
Laboratory testing — considered alongside exposure history, clinical signs, and symptoms — is essential for accurate diagnosis of heavy metal toxicity or mineral nutrient deficiency. The body is an intricate system of checks and balances, with nutritional elements and heavy metals engaging one another and other molecules in a complex biochemical interplay that governs many body processes.
Monitoring heavy metal exposure can alert to insidious accumulation before significant damage occurs. Testing for dietary nutrient deficiencies creates the opportunity to address them through supplementation or dietary changes, while avoiding excessive intake that can itself cause harm. Combining neurotransmitter and element testing provides a far clearer picture of how elemental imbalances contribute to mood disorders and neurological symptoms.
For a comprehensive view of hormones, neurotransmitters, and heavy metals in a single test, explore our Women All-In-One Test — which includes specialist interpretation as standard.
References
[1] Velasco I, Bath SC, Rayman MP. Iodine as Essential Nutrient during the First 1000 Days of Life. Nutrients 10(3) (2018).
[2] Henjum S, et al. Suboptimal Iodine Status among Pregnant Women in the Oslo Area, Norway. Nutrients 10(3) (2018).
[3] Vermiglio F, et al. Attention deficit and hyperactivity disorders in the offspring of mothers exposed to mild-moderate iodine deficiency. J Clin Endocrinol Metab 89(12) (2004) 6054–60.
[4] Dingemans MM, van den Berg M, Westerink RH. Neurotoxicity of brominated flame retardants. Environ Health Perspect 119(7) (2011) 900–7.
[5] Spiller HA. Rethinking mercury: the role of selenium in the pathophysiology of mercury toxicity. Clin Toxicol (Phila) (2017) 1–14.
[6] Wang J, Um P, Dickerman BA, Liu J. Zinc, Magnesium, Selenium and Depression: A Review of the Evidence. Nutrients 10(5) (2018).
[7] Bruning CA, et al. Involvement of the serotonergic system in the anxiolytic-like effect caused by m-trifluoromethyl-diphenyl diselenide in mice. Behav Brain Res 205(2) (2009) 511–7.
[8] Solovyev ND. Importance of selenium and selenoprotein for brain function. J Inorg Biochem 153 (2015) 1–12.
[9] Lin YC, et al. The Methylation Capacity of Arsenic and Insulin Resistance are Associated with Psychological Characteristics in Children and Adolescents. Sci Rep 7(1) (2017) 3094.
[10] Karri V, Schuhmacher M, Kumar V. Heavy metals (Pb, Cd, As and MeHg) as risk factors for cognitive dysfunction. Environ Toxicol Pharmacol 48 (2016) 203–213.
[11] Wu LL, et al. Multiple metal exposures and their correlation with monoamine neurotransmitter metabolism. Chemosphere 182 (2017) 745–752.
[12] Marchetti C. Interaction of metal ions with neurotransmitter receptors and potential role in neurodiseases. Biometals 27(6) (2014) 1097–113.
[13] Mendez-Armenta M, Rios C. Cadmium neurotoxicity. Environ Toxicol Pharmacol 23(3) (2007) 350–8.
[14] Gustin K, et al. Cadmium exposure and cognitive abilities and behavior at 10 years of age. Environ Int 113 (2018) 259–268.
[15] Liu Y, et al. Hearing loss in children with e-waste lead and cadmium exposure. Sci Total Environ 624 (2018) 621–627.
[16] Schofield K. The Metal Neurotoxins: An Important Role in Current Human Neural Epidemics? Int J Environ Res Public Health 14(12) (2017).
[17] Caito S, Aschner M. Neurotoxicity of metals. Handb Clin Neurol 131 (2015) 169–89.
[18] Woimant F, Trocello JM. Disorders of heavy metals. Handb Clin Neurol 120 (2014) 851–64.
[19] Nunes MA, Viel TA, Buck HS. Microdose lithium treatment stabilised cognitive impairment in patients with Alzheimer's disease. Curr Alzheimer Res 10(1) (2013) 104–7.
[20] Schrauzer GN, de Vroey E. Effects of nutritional lithium supplementation on mood. Biol Trace Elem Res 40(1) (1994) 89–101.