A study highlighting the ability of vitamin E to postpone the onset of Parkinson's Disease was published in Neurology this month. Yet other studies, such as the Vitamin E Atherosclerosis Prevention Study reported in Circulation, have failed to confirm the ability of the vitamin to fight disease. A group of European scientists meeting to review and discuss current knowledge on vitamin E and promising lines of future research, have however concluded that the vitamin has been underestimated in the past.
They urged further research to determine exactly how it works and what makes it essential for the human body.
Their conclusions are published in the October issue of the American Journal of Clinical Nutrition, in an article, 'The European perspective on vitamin E: current knowledge and future research.'
The group of scientists, from institutions such as the German Institute of Human Nutrition in Potsdam-Rehbrucke, the School of Health & Life Sciences at King's College London, the Research Institute of Public Health, University of Kuopio, Finland and the Faculty of Health Sciences, University Hospital, Linkoping, Sweden, noted that vitamin E was discovered 80 years ago as a factor essential for reproduction in female rats. Today, the vitamin is established as the most important antioxidant in cell membranes and other lipophilic compartments such as LDL.
As a result, it has been suggested that vitamin E has an important role in the prevention of diseases related to oxidative stress. But, although vitamin E is one of the best researched vitamins, there remain gaps and inconsistencies in existing knowledge.
The scientists discussed basic topics such as vitamin E deficiency, as well as absorption and metabolism of the vitamin. They also covered areas of interest only recently recognised as central to our understanding of the vitamin's actions on the human body. These include tocopherol-binding proteins, which may direct the fat-soluble vitamin to its sites of action within cells, as well as new and specific mechanisms of action beyond its antioxidant properties.
The scientists also discussed the role of vitamin E in conditions and diseases such as cardiovascular diseases, cancer, cystic fibrosis and pre-eclampsia. For example, they evaluated the recent intervention trials on vitamin E and heart disease (HOPE, GISSI, CHAOS, SPACE, ATBC, und ASAP) and highlighted factors which may have influenced the results.
As suggested in the initial hypothesis, vitamin E acts in the early phases of atherosclerosis development, but not in later stages of the disease, noted the group. Participants in these studies, however, largely comprised patients with established atherosclerosis or heart disease.
Also, the trials differed in terms of design, study participants, type and dose of vitamin E given, and substances given together with or in addition to vitamin E. Factors such as vitamin E-status at study entry, bio-availability and compliance were not always considered.
And as men and women differ in their susceptibility to heart disease, effects of vitamin E may differ, so that analysing study results separately for men and women might have been helpful. All these factors should be considered when interpreting the results of these intervention trials, said the experts.
Noting that vitamin E has only just been established as more than 'just' an antioxidant, the scientists said it is 'high time' to determine exactly how it works.
"Future research on this essential vitamin should focus on what makes it essential for humans, why the body apparently utilises alpha-tocopherol preferentially, and what functions other forms of vitamin E have," they concluded.