The recent decision of the American National Cancer Institute to stop a trial which was testing beta carotene as a cure for smoking induced lung cancer has been pilloried for being "politically motivated".

Nutritionists fear the latest trial has all the hallmarks of a Finnish study which came to similar conclusions, only to be discredited later.

They are concerned that the cancer lobby has turned its guns onto the supplement because its beneficial effects have been outlined in more than 200 scientific papers.

The National Nutritional Foods Association, the American trade association for the dietary supplement industry, believes the supposition of the trial was wrong. "No one has ever suggested that beta carotene cures lung cancer," commented the association's executive director Michael Q Ford. "A ridiculous supposition that beta carotene can reverse the ravages of cigarette smoking, and especially among smokers breathing in asbestos could have been reached for far less taxpayer money than the millions that funded this research. The money could have been better spent on smoking prevention and programmes to remove asbestos from the workplace."

The NIC study was abandoned because researchers were concerned that participants in the group receiving supplementation were actually recording more cases of cancer than those given a placebo. They were studying two groups of people 14,000 heavy smokers and 4000 asbestos workers given either placebo or daily doses of 30 mg beta carotene and 25,000 IU of vitamin A (Townsend Letter for Doctors, April 1996).

Better news about beta carotene comes from a new study, which endorses the findings of so many others before it that a diet rich in vitamin C and beta carotene can increase your lifespan.

People who eat two oranges and two carrots a day reduce the risk of death in middle age by over 30 per cent, the researchers found.

They tracked the eating habits of 1,556 men employed by an American telephone manufacturing company for 24 years. Those who were eating appreciably more vitamin A and beta carotene were in particular reducing their risk of developing cancer or heart disease (Am J Epidemiol, 1995; 142: 1269-78).

These findings were at variance with two other studies which found that beta carotene had no especially beneficial effects in reducing the risks of heart disease and angina.

Researchers from the Dartmouth Medical School in New Hampshire could find no strong connection between beta carotene and lower risk of heart problems after studying the reports of 1,188 men and 532 with an average age of 63 (JAMA, March 6, 1996).

Similarly, the National Public Health Institute in Helsinki could find no correlation between vitamin E and beta carotene and reduced risk of angina.

!AJAMA, March 6, 1996.