Vitamin E

Vitamin E is a series of several molecules, approximately 8, that can be divided into two major classifications: tocopherols (saturated side chain) and tocotrienols (unsaturated side chain).¹ Furthermore, tocopherols and tocotrienols can be classified as alpha (α), beta (β), gamma (γ), and delta (δ) based on the positioning of the methyl groups attached to a chromanol ring.¹

Digestion and Absorption: Esterases found in the intestines and pancreas are released to liberate vitamin E from esters.¹ Upon entering enterocytes via passive diffusion, vitamin E is packaged into chylomicrons and enters lymph circulation and then systemic circulation.¹

Circulation, Storage, and Excretion: Lipoprotein lipase in tissues may accept vitamin E within chylomicrons, but the majority is found within the liver as remnants of chylomicrons return from circulation. The liver accepts and releases vitamin E relatively fast; vitamin E  binds to hepatic tocopherol transfer protein (HTTP), preferring a-tocopherol form of vitamin E.¹ HTTP transfers vitamin E into VLDL where it can reside even through conversion of VLDL to LDL and LDL to HDL.¹ Vitamin E  is bound to a protein within cells and can be found in the liver, adipose tissue, heart, lungs, brain, and more.¹

Vitamin E is primarily excreted via the bile (eventually fecal) pathway but can be excreted via skin secretions and urine.¹

Functions:  Ultimately, vitamin E is known for its function as an antioxidant by preventing the oxidation of unsaturated fatty acids found in membrane phospholipids by free radicals termed peroxidation.¹ Free radicals within the body, whether introduced or created via metabolic reactions, contain highly reactive unpaired electrons. Tocopherol binds with free radicals, donating an electron to prevent the free radical from taking electrons from other molecules within cells.¹ ² The oxidized tocopherol can be reduced by vitamin C among other compounds.¹ Due to its antioxidant function, vitamin E has been suggested to play a role in dementia and heart disease prevention. 

Dietary Reference Intake (DRI) - The recommended dietary allowance (RDA) based upon alpha-tocopherol for individuals 14 years or older is 15 milligrams/day.²

Deficiency - Vitamin E deficiency is uncommon but can occur in those with absorptive disorders or liver issues. Abetalipoproteinemia is a genetic disorder in which a lack of apoprotein B can lead to less chylomicron and VLDL synthesis.¹ Vitamin E deficiency can result in cell membrane malformation that can result in anemia and ataxia.¹   

Toxicity - Vitamin E toxicity is uncommon compared to other fat-soluble vitamins. Hypervitaminosis symptoms (lack of appetite, vomiting, nausea, headache, bone and muscle pain, etc) may develop.¹ Excessive vitamin E may interact with vitamin K absorption, vitamin D bone mineralization, and beta-carotene absorption/conversion to vitamin A.¹ 

Dietary Sources of Vitamin E 

Vitamin E is found abundant among plant oils/oil-based products. Fruits and vegetables contain a fair amount of vitamin E as well as fish and nuts.¹ Examples of vitamin E-containing foods include:

Oils/Fats - wheat germ oil, corn oil, safflower oil 

Nuts/Seeds - Almond, peanut, sunflower seeds

Vegetables - spinach, broccoli, asparagus 

Fruits - kiwi, mango, peaches 

Meat - salmon, trout, lobster 

Source(s):

1. Denise M Medeiros and Robert E.C. Wildman, Advanced Human Nutrition, 4th ed. (Burlington, MA: Jones & Bartlett, 2019).

2. https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/