Vitamins and minerals are essential for maintaining normal body system function and for providing protection from oxidative damage. Vitamin E acts as a strong antioxidant, regulates gene expression, and supports immune function. Vitamin E can be consumed in the diet or in supplemental form.
Vitamin E Form and Function
Vitamin E is an essential fat-soluble vitamin that can be categorized into two different isoforms, tocotrienols and tocopherols. Isoforms are proteins that share similar functions but are encoded by different genes and thus have small sequence difference. There are eight different isoforms between these two categories of vitamin E, but the human body may preferentially utilizes α-tocopherol; this is the form that can reverse vitamin E deficiency. The small intestine absorbs all of the various forms of vitamin E, but α-tocopherol is the form predominately re-secreted by the liver for use in the body.1 Additionally, synthetic forms of vitamin E may be found in fortified foods and supplements.
Free radicals are damaging to cells and can contribute to cardiovascular disease and cancer.1 Vitamin E neutralizes free radicals and is then oxidized, becoming inactive. However, other antioxidants, such as vitamin C, can regenerate vitamin E. The antioxidant activity of vitamin E is specific to the prevention of reactive oxygen species (ROS) during fat oxidation. Since fats are an integral component of cell membranes, vitamin E is a powerful force for preventing damage throughout the body. Currently researchers are investigating the potential use of vitamin E to prevent or delay chronic disease associated with free radicals.1
In addition to its antioxidant activity, vitamin E helps regulate gene expression and is an integral part of immune system function. The expression of two enzymes responsible for suppressing arachidonic acid are also increased by vitamin E, which ultimately results in blood vessel dilation and the inhibition of platelet aggregation.2 Recent research in mice suggests that antioxidant effects of vitamin E may be protective against bisphenol A (BPA) toxicity. These preliminary results warrant further investigation in human trials.4
Intake of Vitamin E
The NIH Office of Dietary Supplements currently recommends a daily intake of 15mg of vitamin E for all people 14 years and older. 90 percent of Americans are estimated to fall below this daily intake level.3 Consuming adequate vitamin E from the diet alone can be challenging for individuals. While intake levels are under the recommended dietary allowance (RDA) for most adults, deficiency symptoms are relatively uncommon and are most often caused by an underlying fat malabsorption.2 Vitamin E intake levels have largely been set to prevent deficiency symptoms, and there is growing evidence that higher intakes of vitamin E may reduce the risk of certain chronic conditions like cardiovascular disease, although certain groups should exercise caution and consult with a physician prior to increasing intake above RDA.2
Food Sources of Vitamin E
Vitamin E is found in nuts, seeds, and vegetable oils such as wheat germ, sunflower, safflower, and soybean. Greens such as collards, spinach, and beet contain decent amounts of vitamin E. Some vegetables and fruits like avocado, pumpkin, and mango are also sources of vitamin E.1
Vitamin E and Health
Vitamin E is well known as an antioxidant and for its promotion in many anti-inflammatory processes. In addition, vitamin E can play a role in inhibiting platelet aggregation and strengthen immune functions. Because of these roles, vitamin E has shown to be beneficial in decreasing risk for many diseases and conditions.
Because conditions like age-related macular degeneration (AMD) and cataracts are often related to oxidative stress, vitamin E has shown to help lower the risk of these conditions in certain patients. Studies show that there is a link between high dietary intake of vitamin E and decreased risk of AMD.5,6 Approximately 11 million Americans have AMD to some degree, a number that is only expected to double over the next 30 years.7
The antioxidant properties of vitamin E help reduce oxidative stress in the body. This antioxidant activity supports vitamin E as a potential candidate to improve cognitive health in individuals either at an increased risk for Alzheimer’s disease or those already diagnosed. Because oxidative stress can contribute to the progression of Alzheimer’s disease, many studies have been performed to assess the effects of vitamin E supplementation on improving cognitive decline associated with Alzheimer’s disease. While some studies have shown to be inconclusive, some findings show vitamin E supplementation linked to reduced functional decline in cases of Alzheimer’s disease compared to placebo.8,9
Unresolved inflammation is linked in many inflammatory disease states. Certain forms of vitamin E are known to suppress proinflammatory signaling. These forms include γ-tocopherol (γT) and tocotrienols, which have been shown to reduce inflammation and therefore potentially reducing the risk of inflammatory conditions.10
Reducing Cancer Risk
Certain forms of vitamin E may be inhibitory to certain cancer-promoting pathways and inhibit the growth of cancer cells. The forms most useful in cancer prevention are γT, γ-tocotrienol (γTE), and δ-tocotrienol (δTE); they work to inhibit cancer-promoting pathways, transcription factors, signal transducers, and activation of transcription factor 3. In addition, these forms of vitamin E can promote antiproliferation and cell death in cancer cells through signaling pathways.11,12
Vitamin E supplementation has shown to support immune system function, mainly through reducing the risk of infection especially in older people. Vitamin E supports the immune system by regulating cell division functions and T cell function through its membrane integrity. In addition, vitamin E deficiency is associated with suboptimal immune function.13