Final answer:
Vitamin B12 is a water-soluble vitamin, and while the human body typically excretes excess amounts, toxicity can occur with an overconsumption of supplements. B12 is complex in structure, required in small amounts, and essential for cell metabolism. Deficiencies in B vitamins can lead to serious health conditions.
Step-by-step explanation:
The subject in question is related to the absorption and toxicity of vitamin B12, which is a water-soluble vitamin. Unlike fat-soluble vitamins, which can accumulate to toxic levels in body fat, water-soluble vitamins are generally excreted through urine if consumed in excess. Vitamin B12, along with other B vitamins and vitamin C, is not stored in the body in large amounts, making toxicity from these vitamins rare. However, an exception to this may occur with excessive intake of vitamin supplements. This is pertinent for B12 because even though it is water-soluble, it is a very large molecule and requires intrinsic factor to be absorbed in the gastrointestinal tract. Overconsumption through supplements can lead to hypervitaminosis.
Vitamin B12 was identified as a cure for pernicious anemia, which is not responsive to increased dietary iron. It is notable due to its complex structure, featuring cobalt instead of iron as seen in heme. The body requires only minute quantities of B12, and it plays a crucial role in cell metabolism. B vitamins are generally involved in energy production from food, and deficiencies can lead to conditions such as anemia or beriberi.