Period 5 element dimethyl telluride, (CH)Te, a gas with a garlic-like odor which is exhaled in the breath of victims of tellurium toxicity or exposure. Iodine is the heaviest essential element utilized widely by life in biological functions (only tungsten, employed in enzymes by a few species of bacteria, is heavier). Iodine's rarity in many soils, due to initial low abundance as a crust-element, and also leaching of soluble iodide by rainwater, has led to many deficiency problems in land animals and inland human populations. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities. Iodine is
Vitamin B12 deficiency vitamin B. Elevated methylmalonic acid levels may also indicate a deficiency. A type of anemia known as megaloblastic anemia is often but not always present. Treatment consists of using vitamin B by mouth or by injection; initially in high daily doses, followed by less frequent lower doses as the condition improves. If a reversible cause is found, that cause should be addressed if possible. If no reversible cause is found - or when found it cannot be eliminated - lifelong vitamin B supplementation is usually recommended. Vitamin B deficiency is preventable with supplements containing the vitamin: this is recommended in