The higher the normal body temperature of any species the longer will the average life span of its members be, but the lower the average body temperature of an individual member of that species the greater will that individual’s life expectancy be. Body temperature reflects metabolic rate (the amount of food burned per day per unit of body weight). The lower the metabolic rate the greater the life span, and the higher the metabolic rate the shorter the life span.
In our quest for life extension, therefore, reduction of our personal metabolic activity rate and our core temperature would seem to be highly desirable objectives.
Dietary restriction offers one method of achieving all these objectives, but there may be other methods which can help. In a recent major review of life extension research, the international magazine Newsweek induded discussion of evidence relating to the use of meditation techniques:
A mellow state of mind acts on the body as well as the brain . . . a study reported last year  found that when 73 residents (average age 81) of old-age homes were randomly assigned to groups which either practiced transcendental meditation relaxation, or nothing, the meditation group showed the greatest improvement in blood pressure, memory and survival.
‘Search for the Fountain of Youth’ by Sharon Begley and Mary Hager (Newsweek, 5 March 1990, pages 34 8)
Why should meditation lengthen life? Perhaps because one of its influences involves a slowing down of biological activity. Remember the thousands of mice in Little Rock described in Chapter 5? They received 40 per cent fewer calories than normal laboratory mice and lived twice as long! Mice are known to achieve amazing degrees of life extension, although quite clearly without the benefits of meditation techniques. Part of the physiological change seen in mice on dietary restriction is a reduction of their metabolic rates. Their internal biological activities were slowed down with the very real benefit of reducing free radical activity.
Whether slower metabolic processes (which equals lower body temperature and therefore reduced free radical activity) is achieved by dietary restriction (calorie reduction) or by meditation does not seem to matter at all and, as will be made clear in the section on strategies, a combination of both would seem to be highly desirable. Dietary restriction, however, does not always produce a lower metabolic rate (and lower body temperature).
Weindruch and Walford look at body temperature
It is not surprising that these two key researchers into ageing have also applied their minds to an understanding of the implications of altered body temperatures. In 1979 they were the first to report a major decrease in internal body temperature in mice kept on a dietary (calorie) restriction programme which led to an increased life span. Those mice which were long-lived showed between 1.2 and 2.5°C lower core temperature than did the shorter-lived, fully fed mice. (AU mice had their temperatures taken, rectally, each morning. Weindruch and Walford comment on the displeasure and possible increase in body temperature this produced in them, and suggested that a surgical implant which allows temperature to be monitored without repeated handling of the mice to be a better method!)
They also report on a study conducted by others which confirms these findings. Here life extension was clearly demonstrated in mice receiving 75 per cent of their normal diet, while the core temperature recorded in these animals was 1.5°C lower than fully fed, control animals which did not achieve life extension. The drop in core body temperature is not only seen in ‘normal’ mice, but is observed to be more strongly evident in genetically overweight mice following a dietary restriction programme.
But not rats
Rats, however, do not seem to display the same degree of reduction in body temperature in response to dietary restriction, although there is evidence that some live longer when in a warm environment, a situation which puts a lesser demand on their need to generate heat. For example, Weindruch and Walford tell us of rats living their entire lives in a controlled environment where the temperature was 34°C (93.2°F). Some of these had body temperatures which were higher on average than others. Those with the lower body temperature, in this hot environment, lived an average of 100 days longer than those with high body temperatures, with no dietary modification being involved. The same phenomenon was not seen when the body temperature of rats who lived in a cooler environment (28°C/82.4°F) was measured and compared with their life spans. At this lower temperature the core temperature of animals did not seem to correlate with their length of life.
This points to a life extension advantage (for rats) in having a lower body temperature (slower metabolic rate, more thrifty energy production system), but only when local environmental temperatures are on the high side.
Weindruch and Walford point out that when mice are kept in an environmental temperature of 33°C (91.4°F) they automatically reduce food intake by about a third. Is this self-chosen dietary restriction the reason for their life extension, and not the temperature reduction? And if this effect is seen in mice but not
rats, what implications does it have for humans? In the book The Biology of external Starvation Volume 2(University of Minneapolis Press, 1950) Dr E. Keys describes the drop in human body temperature when enforced calorie restriction is experienced as in the Irish potato famine and (in some cases) during the Second World War. Obviously, in such circumstances undernutrition is accompanied by malnutrition, a quite different situation from that during controlled feeding of fewer calories as part of a nutritious diet. However, we do know that humans respond to calorie restriction and fasting by lowering their core temperatures.
What about external temperature influences?
John Mann (Secrets of Lik Extension. Harbor, San Francisco, 1980) discusses environmental influences on body temperature. He tells us that as far back as 1917 researchers at the Rockefeller Institute lengthened the lives of fruit flies by maintaining their environmental temperature at 6°C (42.8°F) below normal. This technique worked in fruit flies because they are cold-blooded and their environmental temperature could directly reduce their core temperatures. Many subsequent experiments involving coldblooded creatures have replicated these results.
Mammals, however, would react to a cold environment by increasing their core temperature rather than dropping it (and of course this would equal elevated metabolic rate which equals greater free radical activity – not what we are aiming for at all.)
Where cold-blooded organisms (such as tiny sea creatures called rotifers) were both calorie restricted as well as having their temperatures reduced, even greater life extension was achieved: from a normal 18 days to over 50 days. It is worth emphasizing that such a response is almost certainly linked to a reduction in free radical activity brought about by lowered metabolic activity. This is confirmed by evidence from a study performed in Canada at Concordia University, Montreal (Experimental Biology (1980) 15:335-8) which showed that when rotifers (Rotifer philodina) had vitamin E (a powerful antioxidant) added to their culture medium there was a significant increase in both their life span and their breeding potential.
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.
Calorie restriction is another possible way of lowering core temperature, and so anyone using this method in a life extension programme would automatically achieve benefits on the hypothermia front as well. There are, as indicated at the start of this chapter, still other ways of lowering our internal temperature, and these have been employed by Yogis for centuries.
Meditation and similar techniques
Here are some examples of how the mind can be used to control body temperature:
- Impressive demonstrations have been given by people using deep relaxation/meditation methods which produced drops of internal temperature of a degree or more.
- People wishing to learn to control aspects of body function have for many years used a ‘high-tech’ version of meditation, biofeedback, to produce effects such as lowered blood pressure, or increased or decreased temperature of body parts (hands made warmer at will where circulation to the limbs is poor, or the head made cooler in response to an impending migraine, are common examples).
- Techniques currently widely employed to help induce deep relaxation, and which have highly desirable effects on immune function, such as autogenic training, use visualization of alterations in temperature as part of their methodology, with measurable differences in temperature being evident after only a short time.
There is no reason why these and similar techniques could not be investigated more closely to see how they could be modified to produce general hypothermia, and some examples will be found in the section on strategies.
We have now come to the end of the section which looks at the evidence for life extension through different approaches. One theme runs through all approaches, and this is dietary restriction, which seems to influence metabolic rate, body temperature, immune function, growth hormone and free radical activity – all for the better.
In the section on strategies which follows, dietary (calorie) restriction will be the dominant approach outlined. Along with this will come methods suggested by the various chapters on other alternatives, including stimulation of growth hormone production, anti-free radical tactics and ways of influencing core body temperature downwards. None of these is a recommendation. Rather, they are provided for information only, and any decision to use them should be accompanied by suitable professional advice.