Oregon: In the continuing debate over how much vitamin E is enough, a new
study has found that high levels of blood lipids such as cholesterol and
triglycerides can keep this essential micronutrient tied up in the
blood stream, and prevent vitamin E from reaching the tissues that need
it.
The research, just published in the American Journal of Clinical
Nutrition, also suggested that measuring only blood levels may offer a
distorted picture of whether or not a person has adequate amounts of
this vitamin, and that past methods of estimating tissue levels are
flawed.
The findings are significant, the scientists say, because more than
90 percent of the people in the United States who don’t take supplements
lack the recommended amount of vitamin E in their diet.
Vitamin E is especially important in some places such as artery
walls, the brain, liver, eyes and skin, but is essential in just about
every tissue in the body. A powerful, fat-soluble antioxidant, it plays
important roles in scavenging free radicals and neurologic function. In
the diet, it’s most commonly obtained from cooking oils and some
vegetables.
Some experts have suggested that recommended levels of vitamin E
should be lowered. But because of these absorption issues, the
recommended level of 15 milligrams per day is about right, said Maret
Traber, the lead author of this study. Inadequate vitamin E intake
remains a significant societal problem, she said.
“This research raises particular concern about people who are obese
or have metabolic syndrome,” said Traber, who is the Helen P. Rumbel
Professor for Micronutrient Research in the College of Public Health and
Human Sciences at Oregon State University, and a principal investigator
in OSU’s Linus Pauling Institute.
“People with elevated lipids in their blood plasma are facing
increased inflammation as a result,” Traber said. “Almost every tissue
in their body is under oxidative attack, and needs more vitamin E. But
the vitamin E needed to protect these tissues is stuck on the freeway,
in the circulatory system. It’s going round and round instead of getting
to the tissues where it’s needed.”
This research was done with 41 men and women, including both younger
and older adults, who obtained vitamin E by eating deuterium-labeled
collard greens, so the nutrient could be tracked as it moved through the
body. Of some interest, it did not find a significant difference in
absorption based solely on age or gender. But there was a marked
difference in how long vitamin E stayed in blood serum, based on higher
level of lipids in the blood – a more common problem as many people age
or gain weight.
The study also incorporated a different methodology, using a stable
isotope instead of radioactive tracers, than some previous research, to
arrive at the estimates of vitamin E that made it to body tissues. Using
the stable isotope methodology that these researchers believe is more
accurate, they concluded that only 24 percent of vitamin E is absorbed
into the body, instead of previous estimates of 81 percent measured by
the use of radioactive vitamin E.
“In simple terms, we believe that less than one third the amount of
vitamin E is actually making it to the tissues where it’s most needed,”
Traber said.
Vitamin E in the blood stream is not completely wasted, Traber noted.
There, it can help protect LDL and HDL cholesterol from oxidation,
which is good. But that doesn’t offset the concern that not enough of
this micronutrient may be reaching tissues, she said.
Collaborators on this study were from the USDA Human Nutrition Center
on Aging at Tufts University, and the Children’s Nutrition Research
Center at the Baylor College of Medicine. The work was supported by the
USDA Agricultural Research Service and the National Institutes of
Health.