Fat-soluble vitamins play integral roles in a multitude of physiological processes such as vision, bone health, immune function, and coagulation.
The body absorbs these vitamins as it does dietary fats. They do not dissolve in water. Despite structural differences between fat-soluble vitamins, they are absorbed and transported similarly due to their low solubility in hydrophilic media.
After absorption into enterocytes, fat-soluble vitamins become packaged into chylomicrons, which then get secreted into the lymphatic system before entering the bloodstream. Chylomicrons are needed to absorb fat-soluble vitamins and carry fats and cholesterol from the small intestine into the bloodstream. Chylomicrons are metabolized by lipoprotein lipase, which causes the release of fat-soluble vitamins into tissues for use and storage.
While water-soluble vitamins are quickly absorbed with the excess being released, fat-soluble vitamins are slower to dissolve, and the excess is stored in the liver. This means that excessive amounts of fat-soluble vitamin supplements can cause problems such as vitamin toxicity.
Human body can get deficiencies in fat-soluble vitamins when the fat intake is too low or if body cannot absorb it. Some drugs (weight-loss medications) and certain diseases (cystic fibrosis) can cause these problems.
Fat-soluble vitamins
