Vitamin E
Main Characteristics
• Its main characteristic is
antioxidant (inhibits the action of free radicals)
• It is considered important for
the neurological system.
• It was discovered to cause
liver damage, but it can cause kidney failure.
• Its deficiency is rare but can
occur in premature babies or in individuals with problems absorbing lipids.
• It depends on lipids to be
absorbed, therefore being considered fat-soluble.
• Its chemical structure is a set
of vitamin E compounds: tocotrienols and tocopherol, with alpha-tocopherol
being the most available.
• Vitamin E is absorbed by the
small intestine and is transported through the bloodstream by passive diffusion
and is then stored in adipose tissue and the liver and finally incorporated
into a lipoprotein to perform its function in the body. It is only absorbed in
the active form of alpha-tocopherol, which is why supplements are found in the
active form of esters (acetate).
Main Functions and Mechanisms of
Action
• Antioxidant action: involved in
the removal of products of free radical attacks on lipids.
• Action on the nervous system:
prevention of diseases such as Parkinson's and Alzheimer's (prevention of lipid
peroxidation and reduction of oxidative stress).
• Action in the prevention of
cardiovascular disease and diabetes mellitus: due to antioxidant and
anti-inflammatory action.
• Action on the immune system:
increases resistance to infections.
• Beneficial action for those who
practice physical exercise: by reducing damage to tissues caused by free
radicals.
• Action in cancer prevention:
promotes the inhibition of protein kinase C, reducing the risk of cancer.
Bioavailability
• Tocotrienols are absorbed, but
are not converted into the active form in the body, therefore, it is
recommended that they be taken as supplements in the form of esters (acetate).
• The liver is the greatest
regulator of endogenous levels of vitamin E in the body, not only by regulating
the concentrations of alpha-tocopherol, but also by carrying out metabolism and
excretion.
• Regarding the most active form
of vitamin E, the synthetic form is equivalent to half of the absorption
through food, since the fat present in food helps in the absorption of the
vitamin.
Possible interactions
Interaction between nutrients
• Vitamin K: when deficient,
vitamin E can enhance the effects of anticoagulants, increasing blood clotting
time.
• Interactions between vitamins C
and E: For the combination of two antioxidants to be synergistic, the rate of
inhibition of oxidation by both antioxidants must be the same or lower than the
rate of inhibition of each antioxidant alone. The combination of vitamin C and
vitamin E can be effective in inhibiting oxidation. These two antioxidants are
located in different domains, but even so, they interact in the domain between
the membrane and the aqueous phase.
• The cooperation between
vitamins C and E has attracted the attention of many researchers, suggesting a
possible use of both vitamins for therapeutic purposes.
Scientific evidence regarding the
effectiveness of supplementation
• The use of antioxidants for the
prevention and treatment of human diseases has been the subject of study for
more than two decades.
• Diets and vitamin supplements
rich in vitamin E play an important role in diseases related to oxidative
stress, such as cancer, cardiovascular diseases, some hemolytic diseases, among
others.
• In many cases, such as anemia
due to increased oxidative stress, nutritional problems are due to the
continuous depletion of antioxidants resulting from oxidative stress. Vitamin E
deficiency is common in individuals with sickle cell disease, thalassemia and
in those with G6-PD deficiency. It was observed that supplementation with
vitamin E was beneficial in restoring the levels of this vitamin in the plasma,
improving clinical symptoms and reducing the number of irreversible sickled
erythrocytes.
• The action against free
radicals and the protection of lipoperoxidation in the erythrocyte membrane,
through the recycling of vitamin E, makes vitamin C a possibility for the
treatment of hemolytic diseases with increased oxidative stress. In vitro studies
have shown that vitamin C can reduce the formation of Heinz bodies and protect
sickle erythrocytes against oxidative stress.
• Based on studies on oxidative
stress in some hematologic diseases and the possibility of using vitamin C and
vitamin E in the treatment of diseases, the study of antioxidants in the
preservation of oxidative stress caused by oxidizing agents was considered
relevant.
• Several studies have shown that
short-term supplementation with α-tocopherol can be beneficial in children
suffering from sickle cell anemia.
Risks of overdose
Food sources
Foods (100 g) Amount of vitamin E
Hazelnut 24 mg
Olive oil 12.5 mg
Brazil nut 7.14 mg
Peanut 7 mg
Almond 5.5 mg
Pistachio 5.15 mg
Cod liver oil 3 mg
Walnuts 2.7 mg
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