Vitamin E (Tocopherol)

What Is Vitamin E (Tocopherol)?

Vitamin E is a fat-soluble vitamin comprising a family of eight structurally related compounds: four tocopherols (alpha, beta, gamma, delta) and four tocotrienols, each differing in the number and position of methyl groups on the chromanol ring. Alpha-tocopherol is the form preferentially maintained in human plasma and tissues and the only form recognized to meet human requirements, as it is selectively retained by the liver alpha-tocopherol transfer protein (alpha-TTP).

The RDA for adults is 15 mg/day of alpha-tocopherol. The UL from supplemental sources is 1,000 mg/day; high-dose supplementation can interfere with vitamin K-dependent clotting factors.

Key Functions

• Antioxidant protection of cell membranes: Alpha-tocopherol is the primary lipid-soluble antioxidant in cell membranes and plasma lipoproteins, interrupting the chain reaction of lipid peroxidation by donating a hydrogen atom to peroxyl radicals. Vitamin C regenerates oxidized tocopherol.
• Immune function: Supports T-cell proliferation and reduces susceptibility to infection, particularly in older adults.
• Gene expression: Modulates the expression of genes involved in inflammation, cell proliferation, and apoptosis via non-antioxidant mechanisms.
• Platelet aggregation: Inhibits platelet aggregation by interfering with arachidonic acid metabolism, potentially reducing thrombotic risk.

Deficiency and Food Sources

Primary vitamin E deficiency from diet alone is very rare because the vitamin is widespread in foods containing fat. Deficiency most commonly occurs in conditions of fat malabsorption (cystic fibrosis, cholestatic liver disease, abetalipoproteinemia) and causes peripheral neuropathy, ataxia, and pigmented retinopathy.

The richest dietary sources are plant oils — wheat germ oil (approximately 149 mg/100 g), sunflower oil, and safflower oil. Other good sources include almonds (7.3 mg/28 g), sunflower seeds, hazelnuts, peanut butter, spinach, and avocado.