Marc Joseph Nutrition - Blog

New study (full text) out in the journal Archives of Internal Medicine that found that long-term supplementation of vitamin E in generally healthy older women did not significantly reduce the risk of cognitive decline.

But there may be more to the story.

Vitamin E is a powerful, fat-soluble antioxidant that helps to protect fatty substances in the body, such as cell membranes, nerve cells, lipoproteins, etc. Since oxidative stress is commonly observed in neurodegenerative diseases (e.g., Alzheimer’s) at even the earliest stages of the disease process, the thinking is that antioxidants such as vitamin E may help to reduce the onset and/or progression of the conditions.

There are actually eight forms of vitamin E: 4 tocopherols (alpha, beta, delta, gamma) and 4 tocotrienols (alpha, beta, delta, gamma). This study only used the alpha-tocopherol form of vitamin E. In earlier studies looking at vitamin E and cognitive decline, discussion regarding the type of vitamin E used has rarely been included. However, the authors of this study did raise this point (as did an editorial that accompanied the article):

It has been suggested that tocopherols such as {gamma}-tocopherol that is found in foods rather than in supplements* may be more important for delaying brain aging. Although {alpha}-tocopherol has stronger antioxidant properties, {gamma}-tocopherol has important additional anti-inflammatory effects that may enhance neuroprotection.

(* Broad-based vitamin E supplements containing gamma-tocopherol definitely are widely available. Well, at least the authors mentioned the issue.)

Also, recent research suggests that high amounts of alpha-tocopherol
may actually deplete gamma-tocopherol levels in the body. Given this potential, as well as gamma-tocopherol’s unique anti-inflammatory and antioxidant properties (e.g., its ability to inhibit cyclooxygenase and neutralize reactive nitrogen species — the latter especially relevant in protecting nervous system cells), it seems to make more sense to study the effects of a more balanced form of vitamin E on cognitive decline.

Other potential reasons why a beneficial result may have not been observed in this study:

• The dose given (600 IU, every other day) may have been too low.
• The supplements may not have been regularly taken with meals containing fat. Vitamin E is a fat-soluble vitamin and is not well absorbed unless taken with adequate amounts of fat.
• The timing of the initiation and length of the study may have been sub-optimal. Participants in this study were enrolled in their 60’s and given supplements for 10 years. Better results may have been observed if supplementation was started earlier in life and for a longer period.
• Approximately 1/4 of the study participants didn’t comply with the supplementation guidelines, and were thus excluded from the study results.

What would really be interesting to learn going forward is what neuroprotective effects may be offered by more balanced forms of vitamin E given to younger participants in moderate amounts and with meals containing fat. Such an interventional study would obviously take many years to perform in humans. Animal (e.g., mice) studies, although less conclusive, could be performed in the near-term.

Hopefully we’ll continue to see research done in this area, as early intervention is likely the best bet for heading off the progression of cognitive decline into more severe conditions such as Alzheimer’s disease.

This entry was posted on Tuesday, December 12th, 2006 at 8:51 pm and is filed under Alzheimer's, Cognitive Decline, Vitamins. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.