Toxicity of vitamins

Abstract

A number of vitamins (aka micronutrients) are required by our body to maintain metabolic homeostasis, optimal growth, normal physiology, and its functioning. As vitamin deficiencies can give rise to numerous diseases and conditions, excessive consumption of vitamins (aka hypervitaminosis) can also lead to organ or tissue toxicity. AAPCC (American Association of poison control centers) has reported ∼59,761 cases of vitamin exposures in the United States in 2021 alone, of which 42, 784 cases were pediatric and 253 were pregnant exposures. However, vitamins were not listed in the top 25 agents that caused fatalities in the US. Deficiency of vitamin A is associated with significant morbidity and mortality from common childhood infections and is the world's leading preventable cause of childhood blindness. Retinol is the main circulating form of vitamin A in blood and plasma. Vitamin A deficiency also contributes to maternal mortality and other poor outcomes of pregnancy and lactation. Based on biological and chemical activity, and molecular structure, 13 different types of vitamins have been described, and they are divided into two large groups: water-soluble (B vitamins: B1, B2, B3, B5, B6, B8, B9, B12) and vitamin C and fat-soluble vitamins (A, D, E and K), which are stored within fat deposits for long-term use. Fat soluble vitamins take longer to clear from the body and require longer/higher exposures to cause toxicity. Vitamin toxicity also depends upon exposure to the specific types of vitamins, their solubilities, and amount consumed in addition to making certain diet choices. From toxicology perspective, presence of vitamins in the body can influence drug metabolism, GI microflora and absorption of several nutrients. Healthy living depends upon maintaining required levels of vitamins.