Food For Thought

Vitamin E

In his Complete Chinese Cookbook, Kenneth Lo, physicist, writer and renowned Chinese gourmet, records a favourite dish of the people of Beijing and Northern China: yellow flowing eggs. Made basically of eggs, egg yolks, vegetable oils and lard, it makes a shiny, smooth and slippery mixture. And it's packed with vitamin E.

Ginseng, also from the Orient, is brimming with the same. Nobody has yet reported that dementia is less prevalent among Chinese food lovers or fans of Eastern herbal remedies, but recent research into vitamin E might make one wonder. A great deal of evidence suggests that this potent antioxidant (neutraliser of free radicals) could have an important role to play in the treatment of Alzheimer's disease.

Free Radicals: Cellular Vandals

Free radicals are dangerous compounds that can rapidly oxidise proteins, nucleic acids and polyunsaturated fatty acids (PUFAs). There are many different types of free radical, but all owe their reactivity to an unpaired electron in either an atomic or molecular orbital. They form naturally as by-products of cell biochemistry and could cause damage very quickly were it not for a battery of protective enzyme systems. Unfortunately, our cells do not win every battle. Damage accumulates over the years, and this is thought to play a major role in ageing and the pathology of Alzheimer's disease.

Free Radicals and Alzheimer's Disease

PUFAs are important structural units of cell membranes. Brain cells are very rich in lipids and have a particularly high PUFA content. Since PUFAs are attacked by free radicals, these cells are at increased risk of oxidative damage. For some time it has been known that sufferers of Alzheimer's disease show increased peroxidation of lipids in the cells of the inferior temporal cortex. Such peroxidation may even cause the formation of other radicals leading to damage of other cell macromolecules.

Beta-amyloid: A Free Radical Factory

Currently, much attention is focused on the oxidative stress originated by a classic pathological element of Alzheimer's disease - beta-amyloid protein (A beta). A major constituent of the senile plaques that build up in the brains of Alzheimer sufferers, A beta appears to exert a neurotoxic effect through the generation of free radicals.

The first direct evidence that A beta caused nerve cell damage in this way came in 1995. Researchers M. Harris and K. Hensley et al., who had previously shown that A beta in solution generated free radicals, found a strong correlation between radical production and neurotoxicity in cultured hippocampal neurons.

Since then, other authors have confirmed that the full peptide, and even certain fragments of it, are associated with free radical production. As expected, these cause the peroxidation of nerve cell proteins, nucleic acids and membrane lipids. Damage to the latter eventually leads to cell lysis and death.

Natural Protection May Come Too Late

Cells produce enzymes such as superoxide dismutase and catalase to help fight against free radicals. In Alzheimer sufferers, increased levels of these and other protective enzymes have been found. But they only seem to come about as a response to damage already done. In the light of such findings, it is speculated that increased levels of antioxidants might afford protection by neutralising free radicals as they are produced.

Vitamin E - Antioxidant

Vitamin E is very good scavenger of free radicals. It is of special interest as a neuroprotectant since it is lipid soluble - just the kind of thing required to defend fat-rich nerve cells. The evidence that it might do so is reasonable. Old rats given vitamin E seem to remember things for longer. Low serum levels of vitamin E (per unit of cholesterol) have been associated with poor memory in elderly Americans. Similar associations have been seen between low vitamin E levels and Alzheimer and other dementias. And there is also an encouraging report that vitamin E might slow functional decline in people with moderate Alzheimer's disease - though the results are difficult to interpret.

Early studies reported vitamin E to protect against A beta-induced neurotoxicity. It's now thought to reduce A beta-induced free radical damage in embryonic rat hippocampal neurons, to diminish the inhibition of creatine kinase (an oxidation-sensitive enzyme) and prevent the oxidation of proteins. Further, vitamin E-treated apolipoproteinE-deficient mice have been found to perform better in memory tests, a phenomenon attributed to the preservation of nerve dendrites.

Vitamin E - Vascular Protectant

But vitamin E's antioxidant role might also provide benefits via vascular protection. The oxidation of low density lipoproteins (LDLs) is thought to be fundamental in atherogenesis - and vitamin E might slow this down. Many papers report this vitamin to reduce the incidence of cardiovascular disease, and, through diverse non-antioxidant mechanisms, to improve vascular function. If cerebral blood flow is encouraged, the appearance of Alzheimer's disease might be hindered.

Vitamin E: How it Works

eMH asked Dr. Javier de Lucio, lecturer and free radical researcher at the University of Alcalá de Henares, Spain, how vitamin E mops up free radicals.

"Vitamin E, or alpha-tocopherol, protects cell lipids from free radical oxidation. It protects other molecules too by preventing chain reactions that occur when lipids are attacked in this way. Basically, vitamin E has a greater affinity for free radicals, so it's preferentially oxidised by them. It's a kind of sacrificial molecule. In fact, when it's oxidised, it forms another free radical, but one that's far less dangerous. Vitamin C can turn this back into vitamin E, so the molecule is re-usable."

Filling up on Vitamin E

So should we top up with vitamin E? Prof. Rosa Ortega, professor of nutrition at Madrid's Complutense University, gave eMH her advice.

eMH: What are the best sources of vitamin E?

The best sources are eggs, vegetables and vegetable oils, fruits and nuts. Avocado pears contain about 3 mg/100 g, spinach about 2 mg/100 g and eggs about 1.6 mg/ 100g. But almonds and hazelnuts come in with a massive 20 mg/100 g. Boiling doesn't affect the vitamin much, but deep frying can destroy up to 75 % of it.

eMH: How much can or should we take?

Many people don't get what they should. Daily recommended intake is 12 mg for people over 16 years of age - but that's some 600 g of spinach or nearly 2.5 kilos of lettuce! However, one egg should give you about 13% of what you need per day. Some studies suggest that 70 - 300 mg/day should be taken in order to avoid problems like cardiovascular disease, cancer and cognitive impairment. You'd need supplements for that kind of intake.

eMH: Is it safe enough to take without medical supervision?

Vitamin E is one of the least toxic of vitamins, and any excess comes out in the faeces. 'No adverse effect levels' have been fixed at 800 mg/day. But it would be wrong to take it indiscriminately. Anyone wanting to take more should first seek medical advice. Some adverse reactions have been seen in people with low vitamin K levels.

eMH: What kind of health benefits might we expect from an increased vitamin E intake?

Preventing LDL oxidation with vitamin E helps fight cardiovascular disease. If Vitamin E protects against vascular disease it could slow cognitive decline in Alzheimer's disease. Some authors suggest that large doses could help retard functional deterioration in people with moderate forms of the illness.

eMH: So is it a good idea for us to begin taking a little extra before we show any signs of dementia?

High-intake studies have been performed over two year periods, so no-one really knows its effects when taken for any longer. But given its low toxicity, the use of supplements to bring us up to recommended levels - or perhaps somewhat higher - would seem appropriate.

Vivacious Vitamin E

There may be another reason for increasing our vitamin E intake. Enthusiasts have long spoken of its ability to increase our sexual performance! If you don't have the recipe for yellow flowing eggs you might try some homemade mayonnaise - just eggs and olive oil. Not only might you be protecting yourself from mental illness, you may never need to reach for the Viagra® again.