The Chemical Family: Tocopherols and Tocotrienols
When asking, "what is vitamin E also known as?" the answer is not a single word but a group of chemically similar compounds called tocochromanols. This family is further divided into two subgroups based on their chemical structure: tocopherols and tocotrienols. Each subgroup contains four different forms, or isomers, designated by the Greek letters alpha (α), beta (β), gamma (γ), and delta (δ). This brings the total number of naturally occurring vitamin E compounds to eight.
The Tocopherol Subgroup
Tocopherols are the most recognized members of the vitamin E family, characterized by a saturated side chain. Of these, alpha-tocopherol is the most biologically active form in humans and is the only one used to meet human requirements, as determined by the Food and Nutrition Board. It is preferentially maintained in the human body due to a specific alpha-tocopherol transfer protein in the liver. However, the other tocopherol forms still offer significant health benefits, often working synergistically within the body. For example, gamma-tocopherol is the most common form of vitamin E in the American diet from sources like corn and soybean oils, and research suggests it is more effective at trapping reactive nitrogen species than alpha-tocopherol.
The Tocotrienol Subgroup
Less studied but gaining increased attention, tocotrienols are distinguished by their unsaturated side chain containing three double bonds. This structural difference gives them unique biological properties that are not redundant with the tocopherols. For instance, tocotrienols are often lauded for their superior antioxidant potential in certain cellular environments and have been studied for their ability to lower cholesterol and exhibit anti-cancer properties. They are primarily found in specific sources like palm oil and rice bran oil.
The Difference Between Natural and Synthetic Forms
When purchasing supplements, it is also important to consider the distinction between natural and synthetic forms. What is vitamin E also known as in the supplement aisle?
- Natural Vitamin E: This is typically labeled as "d-alpha-tocopherol" or "RRR-alpha-tocopherol". It exists in a single, biologically active form.
- Synthetic Vitamin E: This is commonly labeled as "dl-alpha-tocopherol". It is a mixture of eight stereoisomers, only one of which is identical to the natural form. The natural form is absorbed and utilized more effectively by the body than its synthetic counterpart.
Comparison: Tocopherols vs. Tocotrienols
This table highlights the key differences between the two primary vitamin E subgroups.
| Feature | Tocopherols | Tocotrienols |
|---|---|---|
| Side Chain | Saturated side chain | Unsaturated side chain with three double bonds |
| Biological Activity | Alpha-tocopherol is the most biologically active form in humans and is preferentially maintained by the liver. | Display different biological activities, sometimes more potent antioxidant effects, and unique health benefits. |
| Absorption/Retention | Preferentially retained in the body due to the alpha-tocopherol transfer protein. | Less efficiently retained and more rapidly metabolized than alpha-tocopherol. |
| Common Sources | Sunflower oil, almonds, seeds, wheat germ oil. | Palm oil, rice bran oil, barley. |
| Supplement Availability | Common in most vitamin E supplements, often as alpha-tocopherol. | Increasingly available in specialized supplements, often labeled as mixed tocotrienols. |
What is vitamin E's main role? An Antioxidant powerhouse
One of vitamin E's most crucial functions, regardless of its specific form, is its role as a powerful antioxidant. In the body, it protects cells from damage caused by free radicals, which are unstable molecules formed during normal metabolic processes or through environmental exposure like pollution. Free radicals can harm cells and tissues and are thought to contribute to various chronic conditions over time. By neutralizing these harmful molecules, vitamin E helps maintain cellular health and supports the immune system. Specifically, vitamin E is a fat-soluble antioxidant, meaning it is found primarily in cell membranes, where it protects the fatty acids from oxidative damage.
Key Functions of Vitamin E's Forms
While alpha-tocopherol is the recognized marker for vitamin E status, a holistic view of the vitamin's activity suggests other forms contribute in important ways. For instance, gamma-tocopherol is particularly effective at trapping specific types of reactive molecules, and tocotrienols have shown promise in research related to cholesterol and cancer. The synergistic effects of these compounds underscore the importance of a balanced intake from a variety of whole food sources rather than relying solely on high-dose supplements of a single form. It is why a diet rich in nuts, seeds, vegetable oils, and leafy green vegetables is a better approach for ensuring comprehensive vitamin E benefits.
Conclusion
So, what is vitamin E also known as? It is known by several names, but primarily as tocopherol, which refers to its most common and biologically active form, alpha-tocopherol. However, the broader answer includes the entire family of tocochromanols, encompassing four tocopherols and four tocotrienols. While alpha-tocopherol is the key compound for reversing deficiency, the other forms contribute unique and powerful antioxidant and anti-inflammatory properties to the body's overall health and cellular defense. For optimal benefits, focusing on obtaining a wide range of these naturally occurring compounds through a balanced diet is recommended.
