Vitamins: Vitamin E

Question 1

Vitamin E

Answer 1

• Vitamin E is a generic term for two families of fat-soluble compounds with vitamin E activity: Tocopherols and tocotrienols. Both families contain at least four forms: alpha, beta, gamma and delta. All forms exist within natural foods
• The only form recognized for human nutrition is -tocapherol. The role and use of other forms is still being investigated.
  Tocopherols / tocotrienols = from Greek for ‘to bear a pregnancy’, after being first identified as a dietary fertility factor in rats

Question 2

Food prep

Answer 2

80% of vitamin E is destroyed by freezing, whilst heating destroys about 30% of vitamin E

Question 3

Food sources

Answer 3

Fresh, raw food sources of best:
* Sunflower seeds
* Almonds
* Pinenuts
* Olive oil
* Avocado
* Sweet potato
* Spinach
* Wheatgerm

Question 4

Storage and secretions

Answer 4

The liver takes up all forms of vitamin E asnd preferentially secretes -tocapherol into circulation within lipoproteins.
Circulated everywhere, stored to greatest extent in adipose tissue

Question 5

Polyunsaturated fatty acids and Vitamin E

Answer 5

Polyunsaturated fatty acid (PUFA) intake increases the requirement of vitamin E, due to its antioxidant properties which protect the fatty acid double bonds from oxidation

Question 6

Natural vs. synthetic

Answer 6

 Naturally sourced vitamin E – d-alpha-tocopherol
 Synthetically produced form = dl-alpha-tocopherol
 L isomers are less active. Synthetic form of vitamin E are derived from petroleum oil and should be avoided

Question 7

Measure

Answer 7

Vitamin E is measured in mg of a-tocapherol equivalents:
. 1 mg of the natural a-tocapherol = 1 a-tocapherol equivalent (aTE)

Question 8

Antioxidants: functions and therapeutic uses

Answer 8

• Functions:
  o Protects the following from oxidation:
   Polyunsaturated fatty acids (PUFA) cell membranes
   Nerve sheaths
   Cholesterol (decreases LDL oxidation)
  o A vital ‘chain-breaking antioxidant
  o Vitamins C and selenium support the activity of vitamin E by rejuvenating oxidized vitamin E. so, ensure an adequate intake of all antioxidants to optimize the effects of vitamin E
• Therapeutic uses:
  o Atherosclerosis and cardiovascular disease
  o Male fertility
  o Healthy ageing
  o Cataracts
  o Alzheimer’s and cognitive decline
  o Anti-cancer (also stimulates the P53 tumour suppressor gene)

Chain breaking antioxidant = stops the formation of more unstable radicals

Question 9

Immunity: functions and therapeutic uses

Answer 9

• Functions:
  o Increases phagocyte activity
  o Differentiation of immature T-cells in the thymus
  o Antioxidant and mild anti-inflammatory properties
• Therapeutic uses:
  o HIV/AIDS
  o Healthy immune functioning
  o Infections

Question 10

Anticoagulant: functions and therapeutic uses

Answer 10

• Functions:
  o Inhibits platelet aggregation and vitamin K activity (decreases clotting factors)
• Therapeutic uses:
  o Cardiovascular disease

Question 11

Endocrine: functions and therapeutic uses

Answer 11

• Functions:
  o Improves insulin action (Possibly improves insulin resistance)
  o Modulates oestrogen receptors and activity
• Therapeutic uses:
  o Diabetes mellitus
  o Dysmenorrhoea
  o Menopause (E.g. vagina dryness)

Question 12

Skin repair: functions and therapeutic uses

Answer 12

• Functions:
  o Traditional topical use, although mechanisms not understood
• Therapeutic uses:
  o Scarring
  o Acne

Question 13

Vitamin E deficiency:

Answer 13

A marginal subclinical deficiency is common. Serious deficiencies are rare unless significantly impaired absorption (i.e. cystic fibrosis)
Typically presents as:
 Red blood cell destruction (due to erythrocyte oxidation = haemolytic anaemia) – exhaustion after light exercise
 Easy bruising and slow healing (fewer antioxidants)
 Nerve damage (e.g. neuropathy) due to a oxidation

Question 14

Toxicity and
contraindications

Answer 14

 Rare.
 High doses with vitamin K deficiency and/or warfarin, can increase bleeding risk.
 Caution supplements with chemotherapy.
 High supplement doses create potential for pro-oxidant effect

Question 15

Vit e functions

Answer 15

Immunity
Anti coagulant
Endocrine
Anti oxidant
Skin repair