Unit Converter
Vitamin E (alpha-Tocopherol)
(Primary Fat-Soluble Antioxidant - Protects Cell Membranes, Prevents Oxidative Stress, Supports Neuromuscular and Immune Function)
Synonyms
- α-Tocopherol
- Vitamin E
- d-α-Tocopherol (natural form)
- dl-α-Tocopherol (synthetic form)
- Tocopherols
- Fat-soluble antioxidant vitamin
- Lipid-phase antioxidant
Units of Measurement
- µmol/L
- mg/L
- mg/dL
- mg/100 mL
- mg%
- µg/mL
Unit Conversions
Molecular Weight of α-Tocopherol = 430.71 g/mol
µmol/L ↔ mg/L
1 µmol/L=0.431 mg/L1\ \text{µmol/L} = 0.431\ \text{mg/L}1 µmol/L=0.431 mg/L 1 mg/L=2.32 µmol/L1\ \text{mg/L} = 2.32\ \text{µmol/L}1 mg/L=2.32 µmol/L
mg/dL → mg/L
1 mg/dL=10 mg/L1\ \text{mg/dL} = 10\ \text{mg/L}1 mg/dL=10 mg/L
µg/mL → mg/L
1 µg/mL=1 mg/L1\ \text{µg/mL} = 1\ \text{mg/L}1 µg/mL=1 mg/L
mg/100 mL = mg% = mg/dL
Description
Vitamin E refers to a family of fat-soluble antioxidants, of which α-tocopherol is the biologically most potent and the major form measured in blood.
Key functions:
- Primary lipid-phase antioxidant
- Protects cell membranes from oxidative damage
- Essential for neuromuscular function
- Supports immune health
- Required for normal red blood cell stability
- Important in peroxyl radical scavenging
Vitamin E deficiency is rare but can be severe, especially in fat-malabsorption syndromes and genetic disorders of tocopherol transport.
Physiological Role
1. Antioxidant Protection
Prevents oxidation of:
- Polyunsaturated fatty acids in membranes
- LDL cholesterol
- Mitochondrial membranes
- Retinal photoreceptor lipids
2. Neurological Function
Protects neurons from oxidative stress → deficiency causes:
- Ataxia
- Peripheral neuropathy
- Spinocerebellar degeneration
3. Hematologic Function
Prevents hemolysis of RBCs (especially in premature infants).
4. Immune Function
Enhances T-cell function and immune modulation.
5. Reproductive Health
Important for spermatogenesis and placental protection.
Clinical Significance
LOW VITAMIN E
Clinically important but uncommon.
Causes
- Fat-malabsorption (most common):
- Cystic fibrosis
- Cholestasis
- Biliary atresia
- Chronic pancreatitis
- Celiac disease
- Crohn’s disease
- Cystic fibrosis
- Premature infants
- Abetalipoproteinemia
- Ataxia with Vitamin E Deficiency (AVED - TTPA gene mutation)
- Severe protein-calorie malnutrition
Symptoms
- Peripheral neuropathy
- Ataxia / loss of proprioception
- Muscle weakness
- Visual impairment (retinal degeneration)
- Hemolytic anemia (infants)
- Immune dysfunction
HIGH VITAMIN E
Usually from supplements only (food does not cause toxicity).
Symptoms:
- Increased bleeding tendency (vitamin E antagonizes vitamin K)
- GI upset
- Fatigue
- Headache
- Increased all-cause mortality with extreme doses (>400 IU/day long-term; debated)
Reference Intervals
(Tietz 8E + Mayo Clinic + ARUP)
Serum α-Tocopherol
- 12 – 42 µmol/L
(= 5 – 18 mg/L)
(= 0.5 – 1.8 mg/dL)
Deficiency
- < 12 µmol/L
At-risk infants
- <5 mg/L (11.6 µmol/L)
High level
- 40 mg/L is considered excessive (risk of bleeding).
Diagnostic Uses
1. Evaluation of Fat-Malabsorption Disorders
Central role in cystic fibrosis and cholestatic conditions.
2. Neurologic Symptoms
For unexplained ataxia or peripheral neuropathy.
3. Evaluation of Hemolytic Anemia
Especially in premature infants.
4. Monitoring Supplementation
In people taking high-dose vitamin E.
5. Genetic Disorders
- AVED (TTPA mutation)
- Abetalipoproteinemia
Analytical Notes
- Fasting sample recommended (post-meal lipemia alters levels).
- Protect sample from light.
- α-tocopherol partitions into lipoproteins - interpret with lipid levels if needed.
- Measured using HPLC or LC-MS/MS (gold standard).
Clinical Pearls
- Vitamin E deficiency almost always indicates fat absorption or transport problems.
- Premature infants have low stores and high risk of hemolysis without vitamin E.
- High vitamin E impairs vitamin K - caution with anticoagulants.
- Always evaluate lipid profile if vitamin E levels appear abnormally high or low (lipoprotein-linked).
- AVED presents in childhood with progressive ataxia, treatable with high-dose vitamin E.
Interesting Fact
α-Tocopherol was discovered as a “fertility factor” in rats, which led to the naming of “tocopherol” from Greek:
tókos = childbirth + phérein = to bear.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Fat-Soluble Vitamins
- NIH Office of Dietary Supplements - Vitamin E
- WHO / FAO Fat-Soluble Vitamin Guidelines
- Mayo Clinic Laboratories - α-Tocopherol
- ARUP Consult - Vitamin E Testing
- MedlinePlus - Vitamin E Test