Daily supplements of vitamin E may protect cells from the detrimental effects of oxidative stress in healthy middle-aged to elderly people, says a new study from China.
While the antioxidant power of vitamin E is well established, few human studies exist that support the effects of the vitamin E supplementation on the fluidity of the membrane of red blood cells (erythrocytes), said to be an indirect marker of oxidative stress.
New data published in Nutrition Research indicate that four weeks of supplementation with vitamin E were associated with significant improvements in erythrocyte membrane fluidity, as well as decreased red blood cell rupturing (erythrocyte hemolysis).
“The role of therapeutic doses of vitamin E in protection against certain diseases related to oxidative stress has been supported by epidemiological and experimental data, but vitamin E trials have yielded varied and contradictory outcomes,” wrote researchers from the Medical College of Qingdao University.
“The results of our study help to reduce this confusion.
“Overall, our findings support the hypothesis that dietary supplementation of vitamin E can effectively increase erythrocyte resistance to oxidative stress and improve membrane fluidity in healthy aging subjects.”
There are eight forms of vitamin E: four tocopherols (alpha, beta, gamma, delta) and four tocotrienols (alpha, beta, gamma, delta). Alpha-tocopherol is the main source found in supplements and in the European diet, while gamma-tocopherol is the most common form in the American diet.
The new study used supplements containing dl-α-tocopheryl acetate.
The Chinese researchers recruited 180 health people aged between 55 and 77 to participate in their four-month double-blind, randomized trial. Participants were divided into four groups and randomly assigned to receive vitamin E in doses of 0, 100, 200, or 300 mg of dl-α-tocopheryl acetate per day.
At the end of the study results showed that blood levels of alpha-tocopherol had increased by 71, 78, and 95, respectively.
In addition, levels of malondialdehyde (MDA - a reactive carbonyl compound and a well-established marker of oxidative stress) were significantly decreased in all three vitamin E groups, said the researchers.
Erythrocyte hemolysis was also reduced in the vitamin E groups, with decreases ranging from 20 to 38%. The higher dose vitamin E groups had “dramatic improvements in erythrocyte membrane fluidity”, added the researchers.
“Our results showed that vitamin E supplementation at all 3 dosage levels significantly decreased erythrocyte hemolysis. We also observed significantly improved EMF [erythrocyte membrane fluidity] after 4 months of vitamin E supplementation at the 200 and 300 mg/d dosages, presumably because vitamin E resides primarily in cell membranes where it protects polyunsaturated fatty acids from oxidative damage.”
Source: Nutrition Research
Published online ahead of print, doi: 10.1016/j.nutres.2012.03.012
“Vitamin E supplementation protects erythrocyte membranes from oxidative stress in healthy Chinese middle-aged and elderly people”
Authors: Y. Sun, A. Ma, Y. Li, X. Han, Q. Wang, H. Liang