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Clinician’s Corner: Fat Soluble Vitamins

Now we start our journey through the fat soluble vitamins of A, D, E, K. These vitamins can accumulate and cause adverse effects. Rarely does someone get excess fat soluble vitamins from the diet, but excess supplementation may cause accumulation and potential serious side effects.

Vitamin-A

What it does: Vitamin A is the name of a group of fat-soluble retinoids, which are involved in immune function, vision, reproduction, and cellular communication. Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs

  • Dietary sources: fish liver oils, egg yolks, green leafy, orange & yellow vegetables.
  • Random useless fact: Toxic doses of Vitamin-A if polar bear liver is consumed.

Deficiency States:

  • Night blindness: early sign of Vitamin-A deficiency. May progress to xerophthalmia which is dryness & ulceration of the cornea. May progress to blindness.
  • See decrease in heath and integrity of skin
  • Patients that need Vitamin supplementation include those taking Orlistat (Alli/Xenical), cystic fibrosis patients; however, deficiency is rare in the United States.

Adverse effects: skin & mucus membranes: dry mucus membranes, cheilitis, yellowing of skin, fatigue, nausea, hair loss, headache, vertigo, blurred vision, birth defects, loss of muscular coordination, dry scaly skin. Think of the topical side effects of Accutane (isotretinoin), which is a Vitamin-A analog.

  • Multivitamin supplements typically contain 2,500–10,000 IU vitamin A, often in the form of both retinol and beta-carotene
  • RDAs for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids.
  • Excess Vitamin-A supplementation: leads to increased intracranial pressure (pseudotumor cerebri), dizziness, nausea, headaches, skin irritation, pain in joints and bones, coma, and even death

Smokers should avoid Vitamin-A supplements. Taking beta-carotene actually seems to increase the risk of lung cancer in people who smoke (especially those smoking more than 1 pack per day), former smokers, asbestos exposure, and those who use alcohol (one or more drinks per day) in addition to smoking. Beta-carotene from the diet does not seem to have this adverse effect. (CARET and ATBC studies)

Have a great day on the bench!

Pete Kreckel Thompson Pharmacy Broad Ave