The body-mind connection is often seen as something of an ethereal, pseudo-scientific field. But, 'psychoneuroimmunology' is much more interesting than that.

If anyone was going to get chronic fatigue or ME (myalgic encephalomyelitis), it was going to be Beth. Not that the disease wasn't real – it was just that Beth's whole life seemed to be geared for vulnerability and dependence. Even in the good times, she seemed to have a river of sadness running below the surface, and was almost relieved every time her body succumbed to a bug.

So when chronic fatigue hit, it was as if her friends and family had all been expecting it – here, finally, was something they could define, something they could pin down, a label to allow Beth the time out from the real world she seemed always to crave.

Literature is full of consumptive creative people who lived so long, and so productively, they clearly weren't suffering from anything very debilitating. Healthy they were not; but a coherent explanation for sickliness wasn't forthcoming. Until recently.

What's changed? Well, the mind/mood/body connection has long been treated as so much "wishful-thinking fairy floss". In recent years, however, there's been some very real progress in the world of PNI, or psychoneuroimmunology, the study of how things like mood, stress, and depression impact on the physical body, and particularly, the immune system.

Instead of pseudo-scientific conjecture, the field of psychoneuroimmunology has taken its rightful place as being concerned with the bare glandular pulse of lymph nodes, killer cells and cytokines.

In broad terms, we are talking about a series of complex chain reactions in the body that can translate a stressful few weeks at work into a drop in immunity, possibly leaving you exposed to that cold that is doing the rounds.

So how does it work?

When faced with a stressful situation, your body excretes certain hormones to prime it for a fight or flight response – something which also primes the immune system – for example, by sending immune cells to areas near the skin where they may fight off infection in case of a wound.

Of course fighting or running away isn't a useful response to a stressor like, say, your boss shouting at you, or getting stuck in a traffic jam.

If this only happened occasionally, we wouldn't have had a problem. As it is though, many of us suffer from chronic stress, which results in the immune system getting fed up with constant high alerts. It is a bit like calling the police every day and telling them you're under attack – three months down the line they may still come, but they are hardly going to be at their best.

Similarly, when the immune system is really needed, say to fight off an infection, it may no longer be in peak condition.

In the case of severe stressors, like the death of a loved one, the link between stress and disease has been shown to be particularly strong. Recently bereaved people have been known, for instance, to develop autoimmune conditions, where the body attacks itself.

A positive attitude

Similar interactions between the nervous, endocrine and immune systems are now believed also to have an impact on immunity. Researchers have, for example, noticed that students with an optimistic outlook show healthier levels of immune markers during stressful exams.

Similarly, depression has been linked to a drop in immune function.

Our interconnected bodies

All these connections are highly complex, and still barely understood. Researchers are hard at work teasing out the relationships, and mapping out the fascinating substructure that underlies the relationship between our minds and bodies. What we do now know, however, is that there is a lot of back-and-forth communication between the nervous, endocrine and immune systems.

Research has discovered, for example, that there are cortisol (a stress hormone) receptors on certain immune cells, and large amounts of the neurotransmitter serotonin circulating in areas outside the brain. Both suggest that the lines between the various physiological systems involved are not as separate as once thought.

So what can you do?

As it happens, you can work the system:

    • Stay fit. Exercise boosts the immune system. Thirty minutes of brisk walking, four or five days a week, should do the trick.

    • Antioxidants directly boost the performance of the immune system. Increase your intake of vitamins A, C and E, beta and mixed carotenes, and selenium; and eat lots of fresh fruit and vegetables.

    • Control your stress with daily relaxation techniques.

    • Drink tea. Researchers in Boston found people who drank five to six cups of black tea each day seemed to get a boost in that part of the immune system that acts as a first line of defence against infection.

    • Eat cereal. French and Spanish researchers found that cereal rich with polyphenols such as wheat germ and buckwheat could restore the immune system and extend your lifespan.

    • Pre- and probiotics. Pre- and probiotics are powerful immunity boosters. Prebiotics are food components that improve the food supply of the bacteria in the gastrointestinal tract, so that the beneficial bacteria can grow and flourish – the oligosaccharides (which are fermented and not digested) in soya are a good example. Probiotics are cultures of the beneficial bacteria that occur in the intestinal tract of healthy human beings – they increase the uptake of important minerals from the GI tract thus preventing deficiencies, which lower immunity. Certain yoghurts will give these to you: check the packaging.

    • Essential nutrients. Micronutrients such as vitamin A, iron and zinc, improve immunity in both old and young. Vitamin A reduces the risk of infection. Iron boosts immunity via a number of important enzymes and immunity factors.

    • Cut down on calories. Limiting intake seems to boost key infection-fighting cells, researchers say. In a study done with rhesus monkeys it was found that calorie restriction improved the maintenance and production of T-cells.

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