The amount of the excitotoxin monosodium glutamate (MSG) added to our foods - and, indeed, now to almost all processed foods - has doubled every decade since 1948. The use of another well-known excitotoxin, the artificial sweetener aspartame (also called Nutrasweet or food additive E951), has also soared. It is now estimated that aspartame is in over 9,000 products, many of which (e.g. flavoured crisps, fizzy drinks, jellies) are intended for children.

Excitotoxins (chemicals, usually acidic amino acids,which react with specialised brain receptors) are present in nearly all processed foods, but they are often disguised as "natural flavourings", "spices", "yeast extract", "textured protein", "soy protein extract", etc. Liquid excitotoxins - found in soups, gravies and diet soft drinks - are more dangerous than their dry counterparts because they are absorbed more readily by the body and reach higher levels in the blood and thus in the brain.

In most cases, excitotoxins do not kill people, but they are suspected of worsening the effects of other toxins and thus being the 'final straw' which tips a person from, for instance, a mild, almost harmless form of Parkinson's disease into full-blown Parkinson's. The same goes for many other neurological disorders: migraine, seizures, infections, learning disorders, AIDS, dementia, Alzheimer's, Huntingdon's, episodic violence, etc.

The brains of people with brain disorders like Parkinson's and Alzheimers' disease produce higher levels of glutame (in MSG) and aspartate (in aspartame) naturally, but levels with which the brain can cope in most cases. Introducing more through MSG and aspartame in food may make all the difference and should therefore be minimised by such people.

Many studies have also shown that excessive levels of excitotoxins increased the levels of cancer-causing free radicals, which themselves damage DNA and cell protein. Free radicals have also been shown to prevent astrocytes (star shaped cells) from absorbing excess glutamate in the brain, thus creating a vicious circle leading to spiralling damage.