Introduction
Many studies and clinical trials have been conducted on vitamin E due to its ability to reduce oxidative stress (Miller et al.). These studies have attempted to draw a beneficial connection between vitamin E’s antioxidant nature and conditions like cancer, diabetes, and cardiovascular disease. Unfortunately, many of these studies have had poor results with vitamin E showing little or no benefit in treating these serious diseases. Despite its lack of ability to combat these conditions, vitamin E has shown promise in cataract protection and atherosclerosis prevention. Vitamin E is also commonly used as a topical to help rejuvenate skin and hair. Even with all of these potential benefits, too much vitamin E may be dangerous to a person’s health. Recent studies have suggested that high doses of vitamin E may increase mortality rates (Miller et al.). This finding has caused worry in many professionals who previously believed that mega-doses of vitamin E would not harm patients with serious diseases, even though vitamin E may not have provided any real beneficial effect in combating their ailment.
Definition
Vitamin E is an antioxidant and a fat-soluble vitamin. Like other antioxidants, it protects against harmful free radicals. It is important for individuals to consume antioxidants in their diet to prevent harm to cells, tissues, and organs caused by free radicals (Mayo Clinic). Vitamin E is found in eight different forms in nature. These forms are alpha, beta, delta, and gamma-tocopherols, and alpha, beta, delta, and gamma-tocotrienols (Vukovic). Tocotrienols can neutralize free radicals with greater ease than tocopherols because they move more freely in cell membranes (Block).
Recommendations
Current research recommends that most of a person’s daily vitamin E intake comes from dietary sources as opposed to supplements. However, if an individual chooses to take vitamin E supplements then it suggests that they take no more than 400 IU on a daily basis. The negative effects of mega-doses of vitamin E will be explained further on in this paper. Food sources that provide a healthy form of vitamin E are sunflower seeds, corn oil, kidney beans, spinach, broccoli, kiwi, almonds, and tomato sauce (Mayo Clinic).
Perspective on the benefits of Vitamin E
For the last few decades doctors and consumers alike have praised vitamin E and its antioxidant capabilities. Vitamin E has been hailed as a miracle substance that can provide substantial health benefits such as cataract protection, the slowing of atherosclerosis development, and minimizing the aging process in cells; scientists have even predicted that vitamin E may play a role in stopping diabetes, cancer, and many other diseases that free radicals may cause or worsen.
Vitamin E and Cataract Protection
Cataracts are an optometric condition in which proteins in the lens of the eye become oxidized. Eventually these oxidized proteins form clumps in the lens that obstruct the passage of light. This clumping can be prevented by the antioxidants vitamin E and vitamin C. Approximately 20% of people living in the United States between the ages of 60 and 75 are affected by cataracts annually, which results in half a million surgeries each year. Cataracts are very serious because they can result in blindness (Wickelgren).
A study on adults over the age of 55 with and without cataracts was done in Ontario. The only noticeable difference found between both groups of people was the intake of vitamin E and vitamin C. During a five year period a group of cataract-free adults took at least 400 IU of vitamin E and/or at least 300 mg of vitamin C. Another cataract free group took no supplements and was set aside as a control group. A group’s chance of developing cataracts was 50% less than the control group when only vitamin E was taken. Vitamin C reduced the risk of developing cataracts by 70% (Wickelgren).
Vitamin E and Atherosclerosis
Block’s 2003 review article stated that taking alpha-tocopherol supplements could slow the development of atherosclerosis. Once oxidative stress is reduced there is a chain reaction causing lipid peroxidation and the reduction of LDL oxidative susceptibility. Oxidized LDL can trigger many negative effects. Cholesterol accumulates without regulation because it isn’t properly recognized by LDL receptors and instead attaches to scavenger receptors on macrophages. This can also result in cytotoxicity and immunogenic induction.
In persons with diabetes, oxidative stress increases as a response to decreased levels of antioxidant activity. Several studies found that a strong dose of RRR alpha-tocopherol, which contains 800-1600 IU/d, plays a big part in lowering LDL oxidation for type 2 diabetics. Smaller doses were also tested with less than 400 IU/d and showed no decrease in LDL oxidation. This led the researchers to believe that doses of alpha-tocopherol over 400 IU/d were necessary for maintaining the health of type 2 diabetics (Vega-Lopez).
Perspective on the risks of Vitamin E
High doses of vitamin E have been a topic of concern since the publication of Miller et al.’s meta-analysis on vitamin E supplementation and its negative effects at higher dosages. In this study, it was found that there is a relationship between vitamin E supplementation and all-cause mortality, especially at dosages greater than 150 IU/d (Miller et al.). The meta-analysis also cited several previous studies which indicated that long term, mega-doses of vitamin E could have adverse effects on patients (Miller et al., Dowd and Zheng).
Vitamin E’s interference with Vitamin K’s clotting mechanism
There are many theories as to why vitamin E causes an increased mortality risk. One belief is that vitamin E’s anticoagulant properties may interfere with vitamin K dependent clotting mechanisms (Miller et al.). This is of concern because vitamin E’s properties may cause bleeding that can lead to a hemorrhagic stroke (Corrigan and Ulfers). Alpha-tocopherol affects vitamin K’s clotting mechanism to a greater extent than vitamin E’s other oxidative states (Corrigan and Ulfers).
Vitamin K participates in blood clotting as a coenzyme for a vitamin K dependant carboxylase. The carboxylase activates the inactive clotting factors (II, VII, IX, X) so they can clot blood at the site of an injury. Vitamin E is thought to act as an inhibitor to the vitamin K dependent carboxylase, therefore preventing the clotting factors from becoming active (Dowd and Zheng)( Figure 1). In patients who are ill or who have a vitamin K deficiency, vitamin E’s inhibition of vitamin K’s clotting mechanism may induce clinical bleeding and can cause the patient to exhibit hemorrhagic disease (Corrigan and Ulfers). Giving high doses of alpha-tocopherol (400 IU or greater) to patients who are at risk for hemorrhagic stroke might cause an increase in all-cause mortality in these patients.
Figure 1: How Vitamin E inhibits the clotting mechanism of Vitamin K
Vitamin E as a Pro-OxidantAnother theory is that vitamin E may have a pro-oxidant effect in high dosages (Miller et al.). In the oxidation process of low density lipoprotein (LDL), alpha-tocopherol can act as a pro-oxidant if a co-antioxidant isn’t present (Bowry, Cleary, and Stocker). Free radicals, such as the alpha-tocopheroxyl radical (the product of this process) can cause serious damage to the body; free radicals are thought to play a factor in cardiovascular disease, cancer, Alzheimer’s disease, diabetes, and many other serious ailments. This process may be inhibited by the intake of a co-antioxidant like vitamin C (Miller et al., Bowry, Cleary, and Stocker) (Figure 2). However, several recent studies demonstrate that vitamin C’s (and other co-antioxidants’) ability to stop the pro-oxidant effect of alpha-tocopherol has been overstated. Some trials that combined high doses of vitamin E with other antioxidants showed an increase in mortality in those patients who were a part of the vitamin E groups (Miller et al., MRC/BHF). This finding suggests that high doses of vitamin E, even when taken with a co-antioxidant, may cause problems in the body.
Figure 2: LDL oxidation
Concluding remarks on risks of Vitamin E
While several studies conducted on vitamin E showed no positive effect, there is the possibility of a small benefit with low dosage vitamin E supplementation (Miller et al.). High dosages of vitamin E should not be recommended for public consumption, given the mortality risks associated with dosages of alpha-tocopherol greater than 400 IU/d. In addition to the potential risks of high doses of vitamin E, irregular use of high dosage vitamin E may cause withdrawal effects (Miller et al.). With these findings, high doses of vitamin E (and possibly other high dosage vitamin supplements) should be discouraged.
Interesting side notes about Vitamin E and its effects
Gamma-tocopherol
Recent studies have found that gamma-tocopherol and the tocotrienols may be the reasons for many of vitamin E’s positive effects. Most of the studies conducted in the past few years focused only on the ability of alpha-tocopherol to protect against disease; no other forms were researched nearly as much (Vukovic). Some studies indicate that taking alpha-tocopherol in the commercial form is like taking no antioxidant at all (Block). It is unable to protect against free radicals that lead to degenerative diseases.
Interestingly, Gamma-tocopherol has proven to be a strong antioxidant and anti-inflammatory compound in several studies. The anti-inflammatory nature of Gamma-tocopherol, along with other nutrients, is essential for treating people suffering from atherosclerosis. The properties of gamma-tocopherol reduce the inflammation that takes place in the artery walls. The risk for cardiovascular disease has been shown to be lower in people who have higher blood levels of gamma-tocopherol. Unfortunately, gamma-tocopherol levels are reduced if a person only consumes alpha-tocopherol without any other forms of vitamin E. The over abundance of alpha-tocopherol in the diet is the reason researchers believe that despite vitamin E’s many benefits there may also be some underlying health risks (Vukovic).
Multivitamins sold commercially only contain alpha-tocopherol. Health stores sell multivitamins with all other vitamin E oxidative states and these are strongly suggested by researchers (Block).
Treatment with combinations of vitamin E and other vitamins
Many of the trials listed in Miller et al.’s meta-analysis used vitamin E in addition to other vitamins or minerals as part of their study. Testing other vitamins and minerals in combination with vitamin E could potentially skew the study’s results, showing vitamin E to have more effect on mortality rates than it actually does. Beta-carotene in particular is also known to increase mortality rates at high dosages (Miller et al.).
Discussion
Society assumes that vitamin E and all other antioxidants are nothing but good for you. This may have been overly trusting of vitamin E’s beneficial effects. After reading many articles on the effects of vitamin E we have learned that there isn’t one clear answer on this subject and there is still a great deal of controversy over vitamin E in the research community.
It is really concerning to us that the public isn’t more aware of vitamin E’s potential harmful effects at higher dosages. Many Americans are taking antioxidants like Vitamin E to help reduce their risk of developing heart disease, cancer, and other diseases like Alzheimer’s; some of these individuals are taking mega doses of these antioxidants under the assumption that there are no risk factors. We believe it is important for us, as a society, to err on the side of caution. While antioxidants have shown a lot of promise, we must accept that there may be risks involved with any treatment regimen.
Closing
Vitamin E has been a highly discussed topic since researchers drew a connection between high doses of alpha-tocopherol and increased mortality rates. Until recently, it was believed that vitamin E lacked toxicity; current studies have proven this wrong. According to research, taking large doses of vitamin E does not prolong life and may even shorten it. However, vitamin E in small doses is still beneficial; studies have provided data on the benefits of vitamin E in regards to cataract prevention, slowing the development of atherosclerosis, and decreasing the aging process in cells. Despite the benefits, the potential dangers of vitamin E are a concern that warrants more public awareness.
Works Cited
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