Vitamin E bioavailability isn’t always the same

“Vitamin E” actually is not one single chemical, but instead refers to eight related fat-soluble compounds (shown in Figure 1). Although all eight vitamers are found naturally in foods and absorbed by the body, only α-tocopherol is believed to meet our body’s vitamin E requirements. For simplicity, vitamin E refers to α-tocopherol unless otherwise stated.

Figure 1: The various forms of vitamin E

Vitamin E primarily functions as an antioxidant. Specifically, vitamin E maintains membrane integrity of all cells in the body by preventing the oxidation of the unsaturated fatty acids within their cell membranes. Tissues with cell membranes that are especially susceptible to oxidative damage include the lungs, brain, and retina. Red blood cells and LDL particles are also prone to oxidation.

The recommended daily allowance (RDA) for vitamin E is 15 milligrams per day. Yet, more than 90%^[1] of adults consume less than 12 milligrams per day, with significantly lower intake among individuals who are obese compared to normal weight. Moreover, the RDAs are based on the requirements of healthy individuals, and more than one-third of the US adult population is obese and has metabolic syndrome. It is well established that both obesity^[2] and metabolic syndrome^[3] are linked to increased inflammation and oxidative stress that may increase vitamin E requirements.

The question remains, how does the chronic inflammation associated with metabolic syndrome influence vitamin E bioavailability? The current study evaluated whether co-ingestion of vitamin E with fat could increase its bioavailability for those who need it more, and also evaluated vitamin E pharmacokinetics in healthy participants and participants with metabolic syndrome.

Vitamin E is an essential antioxidant that functions primarily to protect cell membranes from oxidative damage. The study under review sought to evaluate how ingestion of fat could influence bioavailability for both healthy individuals and people with metabolic syndrome, a disease state associated with increased oxidative stress.