When the life span of creatures can be increased by lowering their body temperatures, which reduces free radical activity, as well as by dietary (calorie) restriction, which also reduces free radical activity, and also by the addition of antioxidants such as vitamin E, which too reduces free radical activity, we should be able to assume some common thread. Experiments at Michigan State University have achieved amazing results with flies, through induced hypothermia (lowered body temperature). When flies are kept at 32.8°C (91°F) they live 10 days. However, this can progressively be lengthened to a phenomenal 70 days at an environmental temperature of 25°C (77°F).

One of the chief researchers at Michigan State, Dr Barnett Rosenberg, believes that human life extension to 200 years could be possible if similar techniques could be applied to humans. John Mann discusses the work in this area of Dr Walford, who we have met before working with Dr Weindruch. He tells us that Walford had noted specific variations in the way the immune system responds to hypothermia. For example, animals are found to have a far less efficient immune function when it comes to rejecting foreign tissue (such as a transplant) following hypothermia, whereas their resistance to tumors and infections is greatly increased.

Among Walford's other findings in the way animals respond to hypothermia were an increase in body size, probably a result of increased growth hormone production, and alterations for the better in the type and quantity of cross-linkage, indicating that free radical activity was much reduced as well. Walford has found that application of hypothermia to animals in the second half of their lives is the most effective method of achieving good results, and he is quoted by Mann as having said that if the normal human body temperature of 37°C (98.6°F) - which allows a life span of around 100 years - could be dropped to 35°C (95°F), human life span could be extended to 150 years, while a drop to 33°C (91.4°F) would allow us to live to 180 years (31°C/88°F = 270 years!)

Walford believes that the evolutionary advantages of a higher body temperature have faded since hunting and gathering of food has become less of a feature of life for most of us, and that lower core temperatures would be an advantage for modern humans.

How can we lower our core temperatures?
First we should realize that environmental factors are of secondary importance in altering our core temperature, although there is a clear advantage in them being undemanding. A cold environment calls for both greater metabolic activity and calorie intake with all the negative results that this produces. A pleasantly warm environment, however, reduces metabolic demands and food intake (at least this is true in terms of what is required for heat generation, and is supported by animal studies).

However, our core temperature is not determined by environmental factors directly, but depends rather on internal thermostatic controls which probably lie deep in the brain (in the region called the hypothalamus). Drugs might be used to 're-set' or influence this thermostat, but nothing concrete has been established by research in this direction, as yet, despite the knowledge of a variety of drugs which have the potential to influence core temperature. In any case, such an approach would be fraught with pitfalls and possible side-effects.

Packing the body in an ice bath has been a technique used in surgery as a means of lowering internal (core) temperature for a short time. The dangers inherent in this include the possibility that a reduction of circulation to the brain might affect its function (albeit temporarily). There seems little chance of such a method being practically applicable to life extension programmes, although some hydrotherapy methods might be useful.