MAD DOGS!                                                    Richard J B Willis

'Mad dogs and Englishmen go out in the mid-day sun', as we are constantly reminded when summer comes!  We may not be quite as mad as the world labels us since a new piece of research says that we would benefit from getting regular doses of it.

An excess of sunlight can damage the DNA of the skin and can cause three types of skin cancer.  The message over nearly four decades has been a reminder to use the right factor sunscreen and to cover up against direct sunlight.  It has taken a while to drive that message home, and, just as it is being accepted, studies in the US are now highlighting the importance of making vitamin D and reducing cancer.

An analysis of data from the National Cancer Institute has shown that the incidence of colon, breast and prostate cancers in the US is lower where sun-generated vitamin D is at its highest.  A UK study of over 350 men regarding prostatic cancer seemed to confirm the US observations when it was noted that the quarter of these men who had had the lowest lifetime exposure to the sun were three times as likely to be in the cancer group.

The concept of a little is necessary and too much is positively harmful is called the hormetic effect (from a Greek word meaning to set in motion), and has been observed in some other important areas of health, such as radiation levels.  Nuclear scientists believe that human exposure to ionising radiation (be it x-ray or nuclear fall-out) has a threshold effect.  Below the threshold level impacts are not detrimental.

Evidence for the hormetic effect of radiation goes back to WW2 years when uranium dust thought to be fatal to animals in an experiment showed the opposite effect.  The animals and their offspring were healthier than non-contaminated animals.  In the aftermath of the atomic bombs dropped on Hiroshima and Nagasaki the expected long-term dramatic increase in the incidence of cancers was also lacking.  More recently, following the Chernobyl accident in 1986, Soviet scientists have also been surprised not to see an increase in cancer rates.

Many nuclear scientists are now concluding that having low levels of radiation helps to protect the body against other cancers.  The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), in conducting their own experiments into the effects of radiation, has found that the survival rates of mice and guinea pigs were enhanced when these animals were exposed to small gamma radiation doses and bursts of fast neutrons.

As might be imagined, the hormetic effect is hotly debated, and is undergoing rigorous study especially in cell cultures, bacteria, plants, and other animal studies.  Until the issue has been resolved it is safest to stick to the conventional wisdom – the sunscreen and covers – it's not such a mad idea!