Table 2.
Toxic nutritional elements.
| Nutrients | Foods | Effects | Molecular Targets | Restrictions | Ref. |
|---|---|---|---|---|---|
| Manganese/Mn | Whole grains, clams, oysters, mussels, nuts, soybeans, leafy vegetables and legumes, rice, coffee, tea, black pepper, and other spices | Mn modulates TSH secretion by a dopaminergic mechanism | Part of Mn-SOD | In high doses, pro-antioxidative effect | [24,25] |
| Fluoride/F | Drinking water, fluoride-treated salt | Higher fluoride in drinking water increases hypothyroidism by about twice, iodine deficiency | T3 and T4 iodination | Toxic | [18] |
| Lead/Pb | Polluted air | Increased plasma levels in hypothyroidism, pro-oxidative effects; decreases Se in blood | Thyroid selenoproteins | Toxic | [26] |
| Cadmium/Cd | Smelters, food, burning fossil fuels, plastics, and nickel-cadmium batteries, cigarette smoke, phosphate fertilizers | Oxidative stress and mitochondrial, leading to hypothyroidism and hyperthyroidism; selenium and myo-inositol protect against Cd | MCP-1 and C-X-C motif chemokine 10 expression | Toxic | [18,27,28] |
| Chromium/Cr | High doses from air, foods, or through the skin | Via pleiotropic mechanisms, most of them indirect via insulin, cortisol, Fe, and Se | Oxidation of proteins influences Fe and Se homeostasis | Oxidative changes of proteins | [29] |
| Iron/Fe | Red meat, liver, beans, edamame beans, chickpeas, nuts, dried fruit (apricots), cereals, soybean flour | Facilitates thyroid hormone iodination | Activates thyroid peroxidase | In high doses, pro-antioxidant | [23] |
| Aluminum/Al | Through food, through breathing, and by skin contact | The aluminum ion (Al3+) is harmful. The uptake of aluminum can occur through food, breathing, and skin contact. Long-lasting uptakes of significant aluminum concentrations can damage the central nervous system, leading to dementia, loss of memory, listlessness, severe trembling | AlF4- is a non-specific G-protein activator | In high doses, neurotoxin | [30] |
| Nickel/Ni | Hazelnuts; cocoa and dark chocolate; fruits (almonds, dates, figs, pineapple, plums, raspberries); grains (bran, buckwheat, millet, whole grain bread, oats, brown rice, sesame seeds, sunflower seeds); seafood (shrimps, mussels, oysters, crab, salmon); vegetables (beans, savoy cabbage, leeks, lettuce, lentils, peas, spinach, cabbage); tea from drink dispensers; soya and soya products; peanuts; licorice; baking powder | Contact dermatitis; headaches; gastrointestinal manifestations; respiratory manifestations; lung fibrosis; cardiovascular diseases; lung cancer; nasal cancer; epigenetic effects | Immunotoxic and carcinogenic agent | N/A | [31] |
| Tin/Sn | Tin is present in the air, water, soil, and landfills; it is a normal part of many plants and animals; tin concentrations in foods not packaged in metal cans are minimal; people can be exposed to the tin when consuming food or liquid from tin-lined cans. | Inhalation, oral, or dermal exposure to some organotin compounds has been shown to cause harmful effects in human skin and eye irritation, respiratory irritation, gastrointestinal effects, and neurological problems in humans exposed for a short period to high amounts of organotin compounds. | N/A | Lethal intoxication cases may appear with large amounts but are rare | [32] |
| Gallium/Ga | Found in small amounts in nature and the human body | Acute exposure to gallium (III) chloride can cause throat irritation, difficulty breathing, and chest pain. Its fumes can cause pulmonary edema and partial paralysis. | N/A | N/A | [33] |
| Genistein | Soy and soy foods contain this phytoestrogen belonging to isoflavones | Goitrogenic effect, hypothyroidism | Inhibitor of thyroid peroxidase and sulfotransferase enzymes | Long-term consumption presents a risk for infants and women | [34,35] |
Abbreviations: MCP-1—monocyte chemoattractant protein-1; Mn-SOD—manganese superoxide dismutase.