Vitamin E - Benefits And Functions
Vitamin E is a collective term for a group of fat-soluble vitamins. This group includes a total of eight naturally occurring chemical compounds that are equally divided into two classes of molecules:
- Tocopherols (α-, β-, γ-, and δ-tocopherol)
- Tocotrienols (α-, β-, γ-, and δ-tocotrienol)
Tocopherols are more commonly found in the body than tocotrienols 1.
Vitamin E appears as a thick, yellowish oil 2. It is exclusively produced by cells that carry out photosynthesis and by other photosynthetic organisms such as cyanobacteria 3. Therefore, it must be obtained through diet. Vitamin E is stable in the presence of light, acids, and alkalis 4. However, the levels of vitamin E can decrease at high temperatures and during prolonged food storage.
The essential vitamin is present in the body tissues in all cell membranes, which consist of lipid molecules. 5 6. It is also present in larger amounts in the liver, heart, lung tissue, and skeletal muscles 7.
Vitamin E Absorption
In the intestine, vitamin E is absorbed. Absorption depends on adequate pancreatic function, as well as the secretion of bile acids and the formation of micelles 8. The absorption rates of vitamin E are low but cannot be precisely determined 9. In the blood, vitamin E is transported by plasma lipoproteins (LDL, VLDL, and HDL) and erythrocytes (red blood cells) 10.
Different Bioactivity of Tocopherols and Tocotrienols
Bioactivity describes the benefits of active substances on the organism. The most common and active form of vitamin E in the body is α-tocopherol (also known as RRR-α-tocopherol) 11. Other forms of vitamin E are more selectively broken down and excreted than α-tocopherol, which is retained in the body through α-tocopherol transfer protein (α-TTP) 12.
Approximate biological activity of naturally occurring tocopherols and tocotrienols compared to α-tocopherol 13:
|Name||Bioactivity compared to α-Tocopherol|
In the liver, α-tocopherol is bound to α-TTP. The transfer protein, in turn, allows the incorporation of α-tocopherol into circulating lipoproteins that distribute vitamin E in the body.
Antioxidant Benefits and Functions
Vitamin E is an antioxidant that protects cell membranes and other lipid-containing compounds from damage caused by free radicals. Free radicals are formed during the conversion of food into energy and also by environmental factors such as air pollution and UV light.
Vitamin E protects cell membranes from oxidative damage (lipid peroxidation), which can lead to cell death. Because alpha-tocopherol is fat-soluble, it can fully exert its antioxidant benefits in cell membranes. Vitamin E terminates the chain reaction that leads to lipid peroxidation of polyunsaturated fatty acids and other lipid compounds like LDL (Low-Density Lipoprotein) 14 1516 17. Low-density lipoproteins, which consist of lipids and proteins, transport fats and cholesterol in the bloodstream.
Alpha-tocopherol donates its electrons to the free radicals, thereby neutralizing them. As a result, alpha-tocopherol is oxidized to an α-tocopheroxyl radical. The resulting radical then loses its antioxidant benefit.
The other two forms of vitamin E, gamma-tocopherol and delta-tocotrienol, appear to have more precise antioxidant properties to influence inflammatory response and immune response (the immune system's reaction to foreign substances) in aging and age-related diseases 18.
Vitamin E for Skin Health
Vitamin E is essential for healthy skin. It is found in higher concentrations in the epidermis (outermost layer of the skin) and the dermis (the second layer of skin) 19.
In the skin, vitamin E prevents damage caused by free radicals and reactive oxygen species 20.
Topically applied vitamin E can reduce UV-induced skin swelling, skin thickness, erythema, and edema - all signs of skin inflammation 21.
Further study results show that the intake of vitamin C and E over a period of three months can significantly reduce the sunburn reaction caused by UVB radiation 23. Moreover, the results indicate protection of DNA from damage by antioxidant treatment.
- Skin redness (erythema)
- Skin tanning
- Chronic UV-induced aging
- Skin cancer
Vitamin E also acts as a depigmenting agent, similar to vitamin C 27.
Scientists also believe that vitamin E could absorb energy from ultraviolet (UV) light 28. Additionally, vitamin E may have an anti-inflammatory function in the skin.
The body also requires vitamin E for the immune system. Vitamin E is important for the normal function of immune cells 31.
Furthermore, vitamin E helps to dilate blood vessels and prevents blood clotting within them 32. It increases the release of two enzymes that suppress the metabolism of the fatty acid arachidonic acid, thereby releasing prostacyclin from the endothelium, which expands blood vessels and inhibits platelet aggregation 33. Vitamin E acts as a blood thinner, which can help reduce the risk of heart attack and stroke 34. Accordingly, taking high amounts of vitamin E together with blood thinners is not recommended. Additionally, the intake of additional vitamin E as a blood thinner should be discussed with a doctor.
Vitamin E significantly improves liver function and histological changes (tissue alterations) in patients with non-alcoholic fatty liver and non-alcoholic steatohepatitis (fatty liver hepatitis) 35.
Vitamin C Regenerates Vitamin E
Vitamin C has an antioxidative benefit in the body, similar to vitamin E. Additionally, it can regenerate α-tocopherol from its oxidized form (α-tocopheroxyl radical) 36. For foods rich in vitamin C, click here (table of vitamin C-rich foods).
Possible Interactions with Vitamin K
Vitamin E helps the body utilize vitamin K 37. Additionally, vitamin E and vitamin K have similar chemical structures and share the same metabolic pathways and elimination processes in the body 38. Therefore, there may be an interaction between these two vitamins, although it has not been confirmed 39. You can find foods rich in vitamin K1 here.
Since the brain is highly susceptible to oxidative stress, which accelerates the aging process and is a significant factor in neurodegeneration, studies are being conducted to investigate the benefits of vitamin E on neurological disorders. According to 40, there are ongoing investigations into the benefits of vitamin E on nerve-related diseases.
Based on the study findings from 2008, there is no definitive evidence to suggest that vitamin E has an impact on Alzheimer's disease and its development, as mentioned in 41. Therefore, vitamin E is not explicitly recommended for the prevention of Alzheimer's. However, contrasting results from 2014 associate a high level of vitamin E in the plasma with better cognitive performance and a reduced risk of Alzheimer's development, as stated in 42. For scientists, vitamin E represents a dietary compound that contributes to promoting healthy brain aging and delaying the progression of Alzheimer's. Specifically, alpha-Tocotrienol is associated with a preventive benefit on neurodegeneration, as mentioned in 43.
For other neurodegenerative diseases such as Parkinson's, dementia, and ALS, there are also conflicting results and limited evidence regarding the potential benefits of vitamin E against these diseases. 44 45.
In the treatment of cystic fibrosis, breast diseases, leg muscle pain, and wound healing, vitamin E also does not show any benefit. 46. Furthermore, according to current scientific knowledge, vitamin E does not prevent heart diseases or improve sexual function, athletic performance, and scar healing. 47 48 49.
Most studies indicate that vitamin E does not provide any benefits in the prevention and treatment of cancer. 50. However, newer studies tend to suggest that vitamin E from food and a low dosage of tocopherols may have a preventive benefit against cancer. 51. A study summary from 2015 showed that vitamin E could reduce the risk of renal cell carcinoma and pancreatic cancer. 52 53. Alpha-tocopherol may reduce the risk of bladder cancer, while gamma-tocopherol may increase it. 54. Additionally, studies have shown that excessive dosage of vitamin E supplements with or without selenium can increase the risk of prostate cancer. 55 56 57.
Do vegans have anything to consider?
With a vegan diet, it is very easy to meet the daily requirement of vitamin E. Plant-based foods with a high fatty acid content contain a lot of vitamin E.
Compared to the average population, vegans have higher intake levels of vitamin E, as shown by the results of larger studies. According to the 2002 study, vegans consumed an average of 16.1 mg of vitamin E, while omnivores consumed 11.8 mg 58. The results from 2016 are similar, with vegans consuming 15.6 mg and omnivores consuming 12.1 mg of vitamin E 59.
A smaller study from Denmark also demonstrates higher consumption levels of vitamin E among vegans. Women consumed an average of 15.3 mg (general population - women: 7.1 mg), while men consumed 19.6 mg (general population - men: 7.9 mg) of vitamin E 60.