In most people, aluminium is not as toxic as heavy metals. Aluminium is classified as a non-carcinogen by the United States Department of Health and Human Services. There is little evidence that normal exposure to aluminium presents a risk to healthy adult, and there is evidence of no toxicity if it is consumed in amounts not greater than 40 mg/day per kg of body mass. Most aluminium consumed will leave the body in feces; the small part of it that enters the body, will be excreted via urine. Aluminium that does stay in the body is accumulated in, above all, bone; and apart from that, in brain, liver, and kidney. Aluminium metal cannot pass the blood–brain barrier and natural filters before the brain, but some compounds, such as the fluoride, can.
Aluminium, although rarely, can cause vitamin D-resistant osteomalacia, erythropoietin-resistant microcytic anemia, and central nervous system alterations. People with kidney insufficiency are especially at a risk. Chronic ingestion of hydrated aluminium silicates (for excess gastric acidity control) may result in aluminium binding to intestinal contents and increased elimination of other metals, such as iron or zinc; sufficiently high doses (>50 g/day) can cause anemia. Since aluminium is excreted by kidneys, their function may be impaired by toxic amounts of aluminium. Aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. In very high doses, aluminium is associated with altered function of the blood–brain barrier. A small percentage of people have contact allergies to aluminium and experience itchy red rashes, headache, muscle pain, joint pain, poor memory, insomnia, depression, asthma, irritable bowel syndrome, or other symptoms upon contact with products containing aluminium.