Vitamin E is an essential nutrient for good health, and its major claim to fame is as an antioxidant. It’s one of the first lines of defense when it comes to preventing oxidative damage, and is especially important for protecting cell membranes due to its lipid solubility.
Vitamin E is an abundant vitamin in many vegetable oils and derivative foods including shortening and margarine, and it’s also found in nuts, leafy green vegetables and some fruits. Many people also take a Vitamin E supplement, since it can be difficult to receive the recommended daily intake of the vitamin just from diet alone.
That said, it’s important to understand how the body processes and stores Vitamin E. Too much of the compound can be as harmful (if not worse) as too little. Here’s what you need to know about the pharmacokinetics of Vitamin E.
What are pharmacokinetics?
In simple terms, pharmacokinetics is the study of how the human body reacts to certain compounds, including supplements like vitamins. There are four steps in pharmacokinetics, including absorption, distribution, metabolism and excretion. Understanding the behavior of compounds at each phase of their interaction with the body tells us more about how to use them safely.
How does Vitamin E behave inside the body?
The pharmacokinetics of Vitamin E reveal that it generally has high bioavailability, and depends heavily on the presence of fat. Here’s how it generally behaves once it’s in the body.
- Absorption. Absorption measures how the drug moves from the site of administration to the site of action. Vitamin E is hydrophobic, absorbed like other dietary lipids. It’s solubilized by bile acids and is eventually transported into blood through lymphatics. Absorption is highly dependent on dietary fat in the body, as well as the presence of bile salts and pancreatic enzymes.
- Distribution. Vitamin E follows a long and complex journey through the blood stream where it reaches various tissues throughout the body. Vitamin E is distributed throughout the body by the plasma lipoproteins and erythrocytes. It’s primarily stored in adipose, or fat, tissue and various organs. As Vitamin E enters the body, it’s first sent to the liver where it’s packaged into lipoproteins, which then recirculate throughout the body. Blood transports Vitamin E, which is then taken up by the tissues.
- Metabolism. This measurement describes the process of how the body breaks down the drug. The metabolism of Vitamin E is complex. The liver is the central organ in lipoprotein metabolism, and it’s essential for uptake, distribution and metabolism of Vitamin E.
- Excretion. Excretion refers to the removal of a drug or vitamin from the body. Vitamin E is excreted through two primary routes. The major route of excretion is through bile which is then excreted through feces. After Vitamin E is chain-shortened to make it more water soluble, it’s also passed through urine. Urine is not the primary mode of excretion, though, which makes Vitamin E unique from most water-soluble vitamins.
- Deficiency. Vitamin E deficiency is a very rare occurrence, usually only affecting people with diseases like Crohn’s disease and cystic fibrosis or malnourished individuals. While most American’s do not meet their recommended daily value of Vitamin E from diet alone, it’s generally not a serious health concern for most people.
- Conversion. When you pick up a product like a Vitamin E supplement, you’ll notice measurements expressed both in international units (IU) and alpha-tocopherol equivalent (ATE). There’s a big difference in these measurements, with the IU value only providing surface-level information on the true Vitamin E value of a product. Since other tocopherols and tocotrienols are not included in the IU value, you need to search for more information on the contents of these other forms of Vitamin E.
- Measurement. Alpha-tocopherol is currently the only form of Vitamin E with a standard conversion formula from milligrams (mg) to international units (IU). Other forms of vitamin E, including tocotrienols, are only expressed as milligrams and will appear as such on any product labels.
Vitamin E behaves different depending on the person
Every body is different, and the way Vitamin E, as well as other vitamins and supplements, interacts with one person may be quite different from how they behave in another. While most people fail to get the recommended daily value of Vitamin E from diet alone, it generally doesn’t cause harmful effects. When taken by mouth as a supplement, Vitamin E is likely safe for most people in amounts lower than 1000 mg daily.
If you feel like you could benefit from increasing your daily Vitamin E intake, talk to your doctor to discover if supplementation is an option. In any case, understanding the pharmacokinetics of Vitamin E is an important step in understand how this compound interacts with the body.