“Try thinking of pessimism as a sort of behaviour,” says Professor Martin Seligman of the University of Pennsylvania in Philadelphia, “rather than a way of thinking. She found that optimistic law students had higher levels of disease-fighting killer cells in their blood than did the pessimists “Optimism is an underrated resource,” she says. “It gives you much more than people imagine it does.”All this suggests not only that psychological tests may be able to predict your risk of disease, but that dealing with psychological issues may make you healthier. The Wisconsin researchers, for instance, have shown that regular meditation can increase the amount of activity in the positive left side of the brain.It is also possible to use psychological techniques in order to encourage optimistic thinking. A study of men with Aids discovered that those who held a realistic view of when they were likely to die in fact died an average of nine months earlier than those who were absurdly optimistic about their survival chances.”Optimism seems actually to change the nervous system and boost the immune response, just as being gloomy depresses it,” says Dr Shelley Taylor, a University of California psychologist. Brain-scan studies have already shown that people with a more positive outlook also have more activity on the left side of their brain in the prefrontal cortex (just behind the eye). The Wisconsin scientists ran brain scans on more than 50 people and found that same thing But then they gave all the subjects a flu vaccination.

Six months later, those with the most left-brain activity had the highest level of flu-fighting antibodies in their blood.One of the most intriguing discoveries about optimism is that it seems to be beneficial even when it is unfounded. A link between happiness and a boosted immune system was dramatically demonstrated last autumn by a team from the University of Wisconsin-Madison. The link with a more fearful outlook and Alzheimer’s, for instance, may come via the damage that stress can do to an area of the brain known as the hippocampus, which is involved with forming new memories.But emotions don’t just make you ill; they can also have a protective effect, and here the mechanism involved is different again. Angry men and women have higher levels of an amino acid called homocysteine in their blood.

High homocysteine is increasingly recognised as being directly linked with heart attacks.So the way the link between personality and health works is that negative states are more stressful, and long-term stress makes changes to the immune system, which in turn can have damaging effects on the body and the brain. “Those who eat a raw-food diet, which is high in green plant food, have very clear blood with a slightly alkaline pH and a low amount of fermentation,” says the nutritional microscopist Catherine Daly But not all raw fooders necessarily have healthy blood. Indeed, continues Daly, “those who eat a lot of fruit often have high levels of candida in the blood, while those who eat a lot of nuts often have high mould content. Certainly, some people on a raw-food diet can be considered to be unhealthy. It’s important to know what you’re doing.”"It’s not advisable for people to eat nothing but raw foods for long periods,” adds the author and raw-food revolutionary Leslie Kenton in her latest book, The Powerhouse Diet, “but an all-raw diet can be a wonderful tool for short periods, especially if you are healing something like cancer, Aids or depression.”It’s certainly true that raw foods are used in health institutes and clinics all over the world to aid healing, and when it comes to everyday life, there’s little doubt that incorporating at least some raw food into your diet is beneficial.