kebaldwin
Mon, Aug-27-07, 12:33
Vitamin E doses used in clinical trials may be too low
A report published online on July 4, 2007 in the journal Free Radical Biology and Medicine concluded that insufficient doses of vitamin E could be the reason for disappointing results obtained in some clinical trials which sought to confirm the protective effect of the vitamin against heart attack suggested by epidemiologic and animal studies.
Using an assay they developed to measure F2-isoprostanes formed by oxidative stress, researchers at Vanderbilt University Medical Center determined that it took 16 weeks for a 3200 international unit (IU) daily dose of vitamin E to suppress oxidative stress in participants at risk of cardiovascular disease. This amount of vitamin E is approximately four times as much as doses used in the majority of clinical trials. In another group of subjects, at least 1600 IU was needed to result in a significant reduction in F2-isoprostanes.
The findings identify the flaw in earlier trials that failed to use doses of vitamin E that provided an antioxidant effect sufficient to protect against cardiovascular disease. In decades of vitamin E research, the study is the first to conclusively determine the dose at which the vitamin can be considered an antioxidant drug.
“All of these studies were designed in a way that they never assessed the ability of the dose of vitamin E tested to effectively reduce oxidant stress,” remarked study coauthor Jason Morrow, MD , who is Vanderbilt's chief of the Division of Clinical Pharmacology. “It was clear that large doses – and doses in excess of what all clinical studies had used – were necessary.”
"In the design of clinical trials, one needs to have good surrogate biochemical markers,” he noted. He suggests that F2-isoprostane measurement “really ought to be incorporated into studies assessing disease prevention by antioxidants in general.”
—D Dye
http://www.lef.org/whatshot/index.html#vedu
A report published online on July 4, 2007 in the journal Free Radical Biology and Medicine concluded that insufficient doses of vitamin E could be the reason for disappointing results obtained in some clinical trials which sought to confirm the protective effect of the vitamin against heart attack suggested by epidemiologic and animal studies.
Using an assay they developed to measure F2-isoprostanes formed by oxidative stress, researchers at Vanderbilt University Medical Center determined that it took 16 weeks for a 3200 international unit (IU) daily dose of vitamin E to suppress oxidative stress in participants at risk of cardiovascular disease. This amount of vitamin E is approximately four times as much as doses used in the majority of clinical trials. In another group of subjects, at least 1600 IU was needed to result in a significant reduction in F2-isoprostanes.
The findings identify the flaw in earlier trials that failed to use doses of vitamin E that provided an antioxidant effect sufficient to protect against cardiovascular disease. In decades of vitamin E research, the study is the first to conclusively determine the dose at which the vitamin can be considered an antioxidant drug.
“All of these studies were designed in a way that they never assessed the ability of the dose of vitamin E tested to effectively reduce oxidant stress,” remarked study coauthor Jason Morrow, MD , who is Vanderbilt's chief of the Division of Clinical Pharmacology. “It was clear that large doses – and doses in excess of what all clinical studies had used – were necessary.”
"In the design of clinical trials, one needs to have good surrogate biochemical markers,” he noted. He suggests that F2-isoprostane measurement “really ought to be incorporated into studies assessing disease prevention by antioxidants in general.”
—D Dye
http://www.lef.org/whatshot/index.html#vedu