lipidsoluble

Lipid-soluble, often written as lipidsoluble or fat-soluble, describes substances that readily dissolve in lipids or nonpolar solvents rather than in water. In biology, lipid-soluble compounds are typically hydrophobic or weakly polar and tend to diffuse through lipid membranes and accumulate in fatty tissues or organs rich in lipids.

In the digestive system, lipid-soluble substances are absorbed with other dietary fats. Fats are emulsified by bile acids and form micelles that enable the uptake of lipid-soluble vitamins and lipids by intestinal cells. After absorption, many lipid-soluble compounds are transported in the lymph as chylomicrons and eventually circulate in the bloodstream bound to lipoproteins. They can be stored for longer periods, often in liver and adipose tissue, and released slowly as needed.

Examples of lipid-soluble substances include the fat-soluble vitamins A, D, E, and K, as well as steroid hormones and many lipophilic drugs. The high fat solubility of these compounds explains both their essential roles and potential risks: they can accumulate with excessive intake or in cases of fat malabsorption, and some may cause toxicity if present in high concentrations. Their pharmacokinetic behavior—such as tissue distribution and storage—differs markedly from water-soluble substances, which are typically excreted more readily.

Physicochemically, lipid solubility is often quantified by partition coefficients that compare solubility in lipophilic versus aqueous environments. Higher lipophilicity generally correlates with greater membrane permeability but lower water solubility, influencing absorption, distribution, and elimination.