And, tell you what, it took a couple of coffee-guzzlers at the Bhabha Atomic Research Centre's radiation biology department to establish that fact in a species not particularly known for its love for coffee: mice.

K C George, senior scientist, and his assistant P C Kesavan under the direction of N C Verma, the department head, recently established ``unequivocally'' that mice, when injected with small doses of the much-maligned caffeine, developed resistance to whole-body radiation.

These findings, if successfully extrapolated to human beings, offer a vital key to the prevention of the harmful effects of radiation. They could impact the treatment of cancerous tumours requiring radiation therapy, since coffee is not a regulated substance under any drugs act torequire special dispensation in clinical trials on humans.

They injected 80 mg to 100 mg of caffeine per kg of the bodyweight of the mice (roughly one-third of the lethal dose of 300 mg per kg bodyweight for standard Swiss mouse). The mice were subjected to 7.5 gray of Cobalt 60 gamma rays that ensures 100 per cent fatality in mice within 25 days. The scientists found that at the end of 25 days, 70 per cent of the mice survived and there were no additional deaths till 90 days when the experiment was terminated. In contrast, all the mice not administered caffeine but exposed to the same radiation, died.

Also, a set of mice given only 50 mg of caffeine per kg bodyweight did not survive, indicating an optimal level of caffeine needed to neutralise the effects of radiation. This optimum level, the scientists determined, is about 80 mg per kg bodyweight administered 60 minutes prior to whole body exposure to 7.5 gray of radiation, for mice.

There is also a time-frame involved. For example, a set of miceadministered the same dosage of caffeine just 30 minutes before being irradiated had a survival rate of only 50 per cent as against 70 per cent when the caffeine dosage was administered 60 minutes prior to exposure. There was no radioprotection for mice administered caffeine after being exposed to irradiation they all died within 25 days. The findings are more or less in tune with recent studies tending to liberate caffeine from the negative aspects associated with its ingestion through coffee.

Caffeine, chemically known as 1,3,7-trimethylxanthine, is widely consumed in the form of coffee. An estimated 1,700 million cups containing an average 15,640 million mg of caffeine is guzzled everyday the world over. But about 150 to 200 mg of caffeine per kg of bodyweight is required for coffee to be lethal for humans. Thus, a man weighing 60 kg must consume between 9,000 and 12,000 mg of caffeine everyday for it to be lethal; or between 97 and 130 cups of coffee assuming a cup to contains 92 mg of caffeine on anaverage.

So, what is the optimal level of caffeine presence needed for humans to survive high doses of radiation? Both Verma and George repeatedly warn that the experiments were restricted to mice. When pointed out that the findings might help workers employed in radioactive environments, George said, ``Nothing can be said unless clinical trials are performed on human beings,'' but confirmed that such trials were to be conducted soon.

George, at the moment, is stressing on the medical implications of the findings. He points out that the success rate of radiation therapy on cancerous tumors is minimal, largely because radiation affects the normal tissues surrounding the tumor. To avoid damaging the surrounding areas of a cancer tumor, doctors expose the tumor to a reduced level of radiation than actually needed. Even this does not leave the healthy areas immune.

It is here that caffeine can come in handy, says George. He says caffeine has not only made the cancerous tumour more responsive to lower levelsof radiation, but even offers radio protection to the healthy areas surrounding the tumour. He cautions, however, that a lot more needs to be done before categorical assertions could be made in this regard.

How it works

When a cell is exposed to radiation, its water contents get ionised and damage the DNA and other biological molecules ultimately killing the cell. This route to damage of cells when exposed to radiation is known as the oxic pathway of radiation damage and is used to target and kill cancerous cells. However, even healthy cells around the area exposed to radiation suffer. But if caffeine is present in the system it competes with oxygen for electrons and prevents oxidation and protects the healthy cells.