The curiosity of scientists from Oregon State University (OSU), USA, on how best to conclude on dietary guidelines for vitamin E has shown a surprising new findings that though vitamin E is fat soluble, one does not have to consume fat along with it for the body to absorb it.
Vitamin E in human diets is most often provided by oils, such as olive oil. Many of the highest levels are in foods not routinely considered dietary staples, such as almonds, sunflower seeds and avocados.
The study corresponding author, Traber Maret, a leading authority on vitamin E who’s been researching the micronutrient for three decades explained that before now she and team think they can eat fat and Vitamin E at the same time but now their study have shown that one can wait 12 hours without eating anything, then eat a fat-containing meal.
According to the study published in The American Journal of Clinical Nutrition, vitamin E, known scientifically as alpha-tocopherol, has many biologic roles, one of which is to serve as an antioxidant, said Traber, a professor in the OSU College of Public Health and Human Sciences, and Ava Helen Pauling Professor at Oregon State’s Linus Pauling Institute.
According to the new research, federal dietary guidelines call for 15 milligrams of vitamin E daily (by comparison, 65-90 milligrams of vitamin C are recommended).
“There’s increasingly clear evidence that vitamin E is associated with brain protection, and now we’re starting to better understand some of the underlying mechanisms,” Traber said.
In this latest study, Traber and collaborators used a novel technique involving deuterium-labeled vitamin E, administered both orally and intravenously, to study fractional vitamin E absorption in a group of non-obese, non-diabetic women ages 18-40 with normal blood pressure.
Fractional absorption means just what you would think the fraction of the dose absorbed by the body rather than metabolized and excreted. Fractional absorption dictates how much of something, in this case vitamin E, a person needs to take to maintain the correct level in his or her body.
Deuterium, the vitamin E marker in this study, is an isotope of hydrogen with double the atomic mass of the regular version; deuterium has both a proton and a neutron, compared to just a proton for normal hydrogen, and is a common tracer in investigations of biochemical reactions.
Study subjects at the National Institutes of Health Clinical Center were given both oral and IV vitamin E and drank a liquid meal containing either 40 percent fat or no fat. Researchers then used a combination of tightly controlled dietary intakes to determine the roles fat and fasting played in vitamin E absorption.
“What this study says is, vitamin E gets taken up into the intestinal cell and sits there and waits for the next meal to come along. It’s in a fat droplet, sitting there, waiting to be picked up, like a cargo container, and loaded onto a chylomicron truck”, she noted.
Chylomicrons are lipoprotein particles that transport dietary lipids—fats—around the body through the blood plasma.
The IV portion of the study, used in conjunction with the oral dosing to calculate fractional absorption, also yielded remarkable findings, Traber said.
She continued: “We injected the vitamin E in a lipid emulsion and expected it would take some time to disappear from the plasma and them come slowly back into circulation, but it was gone within 10 minutes.High-density lipoproteins quickly acquired the vitamin E, and the chylomicrons quickly disappeared from circulation into the liver.
“The IV vitamin E we put into the body over three days, almost none of it came out again, like 2% of the dose,” she added. “No one had ever seen that before normally you absorb about half of what you consume. That vitamin E that’s staying in the body, we don’t know where it goes, and finding that out is important for studying how much vitamin E you need to eat every day”.