Fundamentals of Human Nutrition/Vitamin E
7.3 Vitamin E[edit | edit source]
7.3.1 Sources[edit | edit source]
Common sources for Vitamin E include vegetable oils, like canola oil, sunflower oil, safflower oil, olive oil, corn oil, and wheat germ oil. 1 tablespoon of wheat germ oil provides 100% daily value for Vitamin E. (NIH, 2013) Sunflower seeds, almonds, peanuts, and hazelnuts are also good sources of Vitamin E. Some fruits and vegetables also contain Vitamin E, including spinach, broccoli, tomato, kiwi, and mango.
Vitamin E consists of eight different types: alpha-tocopherol, beta-tocopherol, gamma-tocopherol, and delta-tocopherol, as well as alpha-tocotrienol, beta-tocotrienol, gamma-tocotrienol, and delta-tocotrienol, and each type has its own activity within the body (Mayo Clinic, 2013). Alpha-tocopherol is the most active and most popular form of vitamin E in both natural and supplemental forms, and it is referred to as “d-alpha-tocopherol” on nutrition labels of foods and supplements. On the other hand, vitamin E is referred to as “dl-alpha-tocopherol” when manufactured in the laboratory as man-made, or synthetic, vitamin E. However, due to the fact that natural alpha-tocopherol has a higher potency than synthetic alpa-tocopherol, a person would need to consume more synthetic alpha-tocopherol to reap the same benefits of a designated amount of natural alpha-tocopherol (NIH, 2011).
Vitamin E (alpha-tocopherol) is a fat-soluble vitamin that is naturally found in four types of food Vegetable oils, nuts, seeds, and green leafy vegetables (Evert, A). Most known vegetable oils that contain Vitamin E are wheat germ, soya bean oil, and sunflower oil. Example of nuts that have Vitamin E is almonds, and peanuts. Famous seeds that contain vitamin E are sunflower seeds. In addition, green leafy vegetables like spinach and broccoli contain vitamin E. It can also can be found in synthesized food like fortified cereal, and fruit juice (Evert, A). The richest food containing vitamin E is wheat germ oil (Evert, A).. Vitamin E is lost from food in storage slowly over time. For example, wheat flour loses 33% of it vitamin after one year of storage( BRIGELIUS-FLOHÉ, R., & TRABER)..
7.3.2 Functions[edit | edit source]
Vitamin E functions as an antioxidant in the body. Free radicals can cause damage to cells, tissues, and organs. Free radicals are unstable and without one electron, the way they work is by taking a electron from a molecule or a structure, thus leaving it without an electron, making it unstable and changing its function to that of a free radical. Vitamin E stops free radicals from making this damage to the body, by donating one of their electrons to the free radical, thus stopping it from causing any more damage. When Vitamin E gives away its’ electron, it becomes inactive. Doing this stops the oxidation of polyunsaturated fatty acids. Because of its’ role as an antioxidant, some evidence suggests that Vitamin E may protect against hypertention and cardiovascular disease. However, this is shown through a diet of Vitamin E rich foods, as opposed to Vitamin E supplements. (Tangney, 1996)
Years of research has discovered that vitamin E plays important roles as an antioxidant and as a defense mechanism in your immune system. This fat-soluble vitamin helps protect your cells and tissues against damage from free radicals, compounds with an unshared electron that form from daily metabolic processes. Due to their energetic and unstable nature, they seek to react with any other compound to gain an extra electron. Therefore, they can be blamed for different types of cancer, DNA damage, and blood clots that could lead to a heart attack. In response, Vitamin E donates an electron to the free radical allowing it to become more stable and ending the electron-stealing chain reaction. Accumulating studies suggest that vitamin E may lower the risk of heart disease by defending low-density lipoproteins (LDL) against oxidation and lessening inflammation. The oxidation of LDL and inflammation has been associated as key players in the development of heart disease. However, Vitamin E has yet to be proven to prevent cancer, heart disease, dementia, and stroke. Furthermore, it protects and enables the longevity of red blood cells, protects lipids (cell membranes, nervous tissues, and lipoproteins) and helps prevent the destruction of other antioxidants, such as vitamin A and C, from oxidation.
In addition, Vitamin E is very beneficial for skin health. It rejuvenates the skin, promotes healing and reduces the risk of scar tissue developing. It has also been reported to assist with eczema, skin ulcers, cold sores and shingles. Skin is exposed to various environmental elements such as ultraviolet light, having detrimental effects such as skin thickening, wrinkling, edema, erythema and an elevated risk of skin cancer. While Vitamin E can absorb UVB light, it cannot absorb UVA light or light in higher wavelengths of the UVB spectrum and has no effect on the prevention of skin cancers. Also, studies have found a connection between oral supplementation of both Vitamin E and Vitamin C and decreased DNA damage following UV exposure. Application of a topical containing both vitamins before UV exposure has been shown (in animal and human studies) to lower the amount of sunburned cells, lessen DNA damage, hinder erythema, and reduce skin pigmentation following UV exposure. Vitamin E and similar oils have been reported to enhance skin moisture, but data supporting these claims is inconclusive and limited at this time. Oral intake of vitamin E may not provide sufficient skin protection but co-supplementation with vitamin C is more likely to significantly increase the photoprotection of skin by the diet. However, topical vitamin E has been observed to be an effective means of both transport to the skin and manifestation of a photoprotective effect. Vitamin E works as antioxidant. It protects body cells, organs, and tissues from free radical damage. Free radicals are unstable compounds with unshared electron that seek an electron to become more stable. Free radicals end up borrowing the electron from the surrounding environment like cells, organs, and tissues(vitamin E, Harvard). Damaging cells and making them unstable in the process. Antioxidants like vitamin E and selenium donate their own electron instead to the free radical, protecting the surrounding environment in the process. Free radical damage has been connected to many issues like cancer, aging, and cardio vascular disease. Vitamin E supplementation was thought of as a promising cure. However, recent studies have been controversial where both negative and positive effects were seen from using Vitamin E supplements. For example, HOPE, a study that found people who have heart disease that took vitamin E supplementation for 4 years had a higher chance of heart failure(vitamin E, Harvard). Whereas, in another study when Vitamin E supplement were given to healthy people it was linked to 24% lower risk of cardiovascular disease (vitamin E, Harvard). At last, a study found no effect of vitamin E supplementation to cardiovascular disease. Which lead the scientist to come up with a conclusion that Vitamin E has potential benefits only in certain subgroups. Same controversial findings are found with cancer (vitamin E, Harvard). Other than being an antioxidant, Vitamin E also helps keep the strength of the immune system. it In addition, it is involved in cell signaling. Vitamin E interacts with body use of vitamin K. Therefore, it has a role in the formation of red blood cell and clotting.
Vitamin E Fact Sheet for Health Professionals. (2013, June 5). Retrieved November 30, 2015, from https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/ Michels, A. (2012, February 1). Vitamin E and Skin Health. Retrieved December 3, 2015, from http://lpi.oregonstate.edu/mic/micronutrients-health/skin-health/nutrient-index/vitamin-E#functions Vitamin E. (2011, October 24). Retrieved November 30, 2015, from http://www.nutri-facts.org/eng/vitamins/vitamin-e-tocopherol/at-a-glance/ Wax, E. (2015, February 2). Vitamin E. Retrieved November 30, 2015, from https://www.nlm.nih.gov/medlineplus/ency/article/002406.htm
7.3.3 Requirements[edit | edit source]
The dietary requirements are for the alpha-tocopherol form of Vitamin E only, because alpha-tocopherol is the only form of Vitamin E that is kept in the body. The Recommended Daily Allowances (RDA) for Vitamin E in adults is 15 mg per day. The RDA for males and females are the same, unless the female is lactating, then the RDA increases to 19 mg per day. The Upper Level (UL) of Vitamin E for adults is 1000 mg per day.
The recommended daily allowance (RDA) for Vitamin E is actually for a specific type of vitamin E called alpha-tocopherol (Vitamin E, National institute). Vitamin E is a group name for 8 fat-soluble compounds (Vitamin E, National institute). In which alpha-tocopherol is part of the 8, it has the highest biological activity, and is the only one retained in the plasma (BRIGELIUS-FLOHÉ, R., & TRABER,). The RDA differs according to gender, and age. RDA for adults 15+ is 15 mg for genders (Vitamin E, National institute). Whereas, the RDA for 9 to 13 years old children is 11 mg for both genders (Vitamin E, National institute).
7.3.4 Deficiency[edit | edit source]
Vitamin E deficiency is very rare. People with fat malabsorption diseases, like cystic fibrosis and Chron’s disease are more likely to develop a vitamin E deficiency. Malabsorption disease prevents the bowel to absorb nutrients or pertinent fluids. Lack of absorption prevents Vitamin E from doing its’ job- stabilizing free radicals as part of the antioxidant process. Vitamin E deficiency can cause erythrocyte hemolysis, which is when red blood cells break open, due to the oxidation of polyunsaturated fatty-acids in the cell’s membrane. Vitamin E deficiency can cause muscular and neurological problems, anemia, and retinopathy. Treatment is usually Vitamin E supplementation.
Recent studies have shown that many Americans do not usually consume enough vitamin E, and specific populations who may not be getting enough vitamin E due to their general diet patterns include Hispanics and Non-Hispanic blacks, children between 4 and 18 years old, adults above 51 years old, and those who are clinically diagnosed as obese (Vitamins and Minerals, 2007). However, most people do not visibly display specific physical signs of vitamin E deficiency and may seem healthy otherwise.
Although severe vitamin E deficiency is rare, research has found that many americans suffer from marginal vitamin E deficiency. According to the US National Health and Nutrition Examination Survey III (NHANES III), approximately 90% of American adults do not meet the daily requirement of vitamin E. This marginal deficiency could be due to several factors. One of these factors is smoking. Research has shown that cigarrette smoke causes oxidative stress due to the free radicals in the smoke.(Bruno and Traber, 2005) As the body attempts to battle these free radicals vitamin E storages are depleted as the vitamin functions as an antioxidant.
There are also some health conditions and illnesses that can contribute to deficiency of Vitamin E. For example, some infants that are born prematurely and are underweight are vitamin E deficient. One must be cautious of treating this deficency in enfants with vitamin E supplementation because it can increase the risk of infection. Vitamin E is a fat soluble vitamin, meaning that fat is required to absorb it. This is why people with fat-malabsorption disorders are more susceptible to deficiency. In a rare inherited disorder known as abetalipoproteinemia, people are unable to absorb dietary fat efficiently, which also leads to deficiency. People suffering from this disorder need large amounts of supplemental vitamin E. Another inherited disorder is Ataxia and vitamin E defiency, otherwise known as AVED. In individuals with AVED, the liver's vitamin E transfer protein is either defective or not present. Their deficiency is so extreme that without large quantities of supplementation, they can develop nerve damage and ultimately become unable to walk. Aside from nerve damage, severe deficiency in vitamin E can yield other neurological symptoms. These include impaired balance, myopathy or muscle weakness, and retinopathy or damage to the retina.
Deficiency Treatment for Neurological and Absorption Disorders
Research has concluded that correcting vitamin E deficiency can result in the reversal of some neurological symptoms as well as balance vitamin E levels in people with absorption disorders (Sokol, 1988). Within a 5 to 15 year span, retinal degeneration in people with abetalipoproteinemia can be stabilized by large oral doses of a vitamin E supplement. For this symptom, it is recommended to take 2 to 3 doses totaling 100 to 200 mg per day. In addition to this, 15,000 to 20,000 IU/day of vitamin A can help reverse retinal degeneration. In patients with cystic fibrosis, 5 to 10 IU/kg/day is sufficient for balancing vitamin E levels. People with absorption disorders tend to show improvement in vitamin E levels after following a daily regimen of 200 to 3600 mg. Vitamin E deficiency is rare, and symptoms do not appear if a person is getting a little amount of vitamin E. However, in special cases deficiency is an issue. For example, low birth weight infant < 1500 grams have vitamin E deficiency (Vitamin E, National institute). Since vitamin E is fat soluble people with fat-malabsorption like abetalipoproteinemia are vulnerable for Vitamin E deficiency. They would need to consume a lot of Vitamin E than normal to meet the requirement, around 100 mg/kg (Vitamin E, National institute). Deficiency symptoms are peripheral neuropathy, Atherosclerosis, and impairment of the immune response (Vitamin E, National institute). Atherosclerosis forms because of the inability to protect LDL from free radicals. Other symptoms are Muscle weakness, and damage to the retina (Vitamin E, National institute). References: 1. Oregon State University, Linus Pauling Institute, Micronutrient Information Center http://lpi.oregonstate.edu/mic/vitamins/vitamin-E Retrieved November 30, 2015
2. National Institutes of Health, Health Information, vitamin E https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/ Retrieved November 30, 2015
3. Bruno and Traber, Cigarette Smoke Alters HUman Vitamin E Requirements. The Journal of Nutrition. April 1, 2005 vol. 135 no. 4 671-674 http://jn.nutrition.org/content/135/4/671.full Retrieved November 30, 2015 4. Sokol, R. J. (1988). Vitamin E deficiency and neurologic disease. Annual Review of Nutrition, 8, 351-373. doi:10.1146/annurev.nu.08.070188.002031 [doi] Retrieved November 30, 2015 http://www.annualreviews.org/doi/pdf/10.1146/annurev.nu.08.070188.002031
7.3.5 Toxicity[edit | edit source]
Vitamin E toxicity is very uncommon, and is not usually achieved from intake from foods. However, Vitamin E toxicity can occur from excessive supplements. Excessive amounts of Vitamin E can mess up Vitamin K’s clotting ability and cause blood to thin, increasing the possibility of hemorrhage. (Kaahe, 2013) While vitamin E is relatively harmless if consumed in excess through the diet (although unlikely), those who take vitamin E supplements should be aware of its interactions with certain medications. For example, people on anticoagulant or antiplatelet medication, such as warfarin, also known as Coumadin, should consult their doctors for possible heightened risk of bleeding due to its interactions with vitamin K’s coagulation function. Also, supplemental vitamin E taken along with other antioxidant vitamins can reverse the benefits of taking statin and niacin drugs together to prevent heart complications. Lastly, vitamin E supplements can have an impact on chemotherapy or radiation therapy treatment for cancer, which could have serious effects (NIH, 2011). These examples of possible negative outcomes of excess vitamin E support the fact that supplemental vitamin E is not currently recommended as a necessary addition to the diet if a person is consuming enough vitamin E through their regular diet.
However, those who are already taking vitamin E supplements or those considering taking supplements may decide to take a one-a-day multivitamin-mineral supplement as opposed to a vitamin E-only supplement. Whereas the multivitamin-mineral supplements contain an average of 30 IU (international units) per pill, vitamin E-only supplements can contain anywhere from 100 to 1,000 IU of vitamin E per pill. While both amounts are above the daily recommended amount of 22.4 IU (15 mg), the extremely high amount of vitamin E in vitamin E-only supplements that can go as high as 1,000 IU (which is well over the recommended daily upper limit of 1000 mg) is unnecessary, and there is little to no evidence for vitamin E supplements’ impact on overall health or on lowering the possibility of contracting diseases related to vitamin E deficiency (NIH, 2011).
Tangney, C. (1996). Vitamin E and Cardiovascular Disease. Nutrition Today, 13-22. Retrieved August 4, 2015, from http://www.researchgate.net/publication/232156492_Vitamin_E_and_Cardiovascular_Disease
Vitamin E - Vitamin E Toxicity - Health Encyclopedia. (2013). Retrieved August 4, 2015, from https://www.kaahe.org/health/en/915-vitamin-e/915-6-vitamin-e-vitamin-e-toxicity.html
Vitamin E. (2013, June 5). Retrieved August 4, 2015, from https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/
Vitamin E. (2011, October 11). Retrieved November 29, 2015, from https://ods.od.nih.gov/factsheets/VitaminE-Consumer/
Vitamin E. (2013, November 1). Retrieved November 29, 2015, from http://www.mayoclinic.org/drugs-supplements/vitamin-e/background/hrb-20060476
Vitamins and Minerals: How to Get What You Need. (2007, October 1). Retrieved November 29, 2015, from http://familydoctor.org/familydoctor/en/prevention- wellness/food-nutrition/nutrients/vitamins-and-minerals-how-to-get-what-you-need.html
Whitney, E., & Rolfes, S. (2002). Understanding nutrition (9th ed.). Belmont, CA: Wadsworth.