Fat-soluble vitamins A, D, E, and K (ADEK)

Fat-soluble vitamins A, D, E, and K are a group of essential lipophilic micronutrients that play diverse and critical roles in human physiology [1.1.2, 1.2.1]. Vitamin A (retinoids) is vital for vision, immune function, and cellular differentiation; Vitamin D (calciferol) acts as a pro-hormone regulating calcium homeostasis and bone health; Vitamin E (tocopherols) serves as a primary lipid-soluble antioxidant protecting cell membranes; and Vitamin K (phylloquinone/menaquinones) is essential for blood coagulation and bone metabolism [1.2.1, 1.2.3, 1.4.3]. Unlike water-soluble vitamins, these are stored in the liver and adipose tissue, which allows for long-term storage but also increases the risk of toxicity (hypervitaminosis) upon excessive intake [1.1.1, 1.3.1]. They interact with various therapeutic agents, such as orlistat and bile acid sequestrants which impair their absorption, and warfarin, which antagonizes the action of Vitamin K [1.2.3, 1.3.1, 1.4.4]. Clinically, they are used to treat deficiency syndromes like rickets or night blindness, and their signaling pathways (e.g., VDR, RAR) are targets for drugs treating osteoporosis, psoriasis, and certain cancers [1.1.2, 1.2.2, 1.4.1].

Other names

Lipophilic vitaminsADEK vitaminsFat-soluble micronutrients

Vitamins A and D function primarily by binding to nuclear receptors (RAR/RXR and VDR, respectively) to modulate gene transcription [1.2.1, 1.4.3]. Vitamin E acts as a chain-breaking antioxidant that neutralizes free radicals to prevent lipid peroxidation in cell membranes [1.2.1, 1.2.4]. Vitamin K serves as an essential cofactor for the enzyme gamma-glutamyl carboxylase, which is required for the post-translational carboxylation of clotting factors II, VII, IX, and X [1.2.1, 1.4.3].