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Have you recently quit smoking, but you're still tormented by sporadic cravings to light up? Try a five-minute walk the next time you get the urge.

Canadian and British researchers recently completed a study that suggests relatively brief bursts of exercise can aid smokers in kicking the habit.

Previous research had already indicated that exercise might have a role to play in controlling these temptations.

So, the research team examined the results from 12 earlier laboratory trials in which scientists carefully measured the effects of physical activity on the urge to smoke.

The overall findings revealed that short bouts of physical activity -- lasting as little as five minutes -- can reduce the cravings and alleviate the withdrawal symptoms associated with giving up smoking, according to the new study published in the journal Addiction.

"Not everyone can jump on an exercise bike for 40 minutes. But you might be able to go for a brisk five-minute walk if you get a craving for a cigarette," one of the researchers, Guy Faulkner of the University of Toronto, said in an interview.

The study leader, Adrian Taylor of the University of Exeter in Britain, said, "If a drug revealed the same effects, it would immediately be marketed as a valuable aid to help people quit or cut down."

The researchers are not sure why small amounts of exercise seem to have such a big effect.

"The common-sense explanation is that it is a distraction," Dr. Faulkner said. In other words, a brief walk might simply take your mind off the nagging desire to smoke.

The researchers are also pursing a theory that exercise could alter brain chemistry.

"Exercise may result in an increase in dopamine, which affects the appetite . . . for a cigarette," Dr. Taylor said in an e-mail.

But regardless of how it works, it seems to do the trick.

And, Dr. Taylor noted, exercise is certainly a healthier thing to do than eating more food -- a common way of coping with tobacco withdrawal symptoms.

Food gone bad

U.S. scientists are developing a "dipstick" testing kit that will determine whether food is safe to eat.

"The idea is to have a device that you can carry with you so that you can check the quality of foods while away from home, such as in a restaurant," said John Lavigne, who is leading the project at the University of South Carolina.

During the past week, the researchers presented their latest scientific results at a meeting of the American Chemical Society in Chicago.

The new test relies on the detection of a class of chemicals called non-volatile biogenic amines, which are produced when bacteria break down proteins in foods. It is essentially an indirect measure of food spoilage.

The disposable dipstick changes colour within five minutes if it touches food that has gone bad.

"This test can be used on any food [either cooked or raw] containing proteins and this covers many foods -- fish, meats, dairy products, beer, wine, vegetables, fruits, nuts and even chocolate," Dr. Lavigne said in an e-mail.

The researchers hope to have their testing kit on the market in two or three years.

It is bound to attract a lot of attention because food poisoning is extremely common.

In Canada alone, public-health experts estimate there are between 11 million and 13 million cases of food-borne illness every year.

Sunshine and asthma

Pregnant women who get ample amounts of vitamin D may be protecting their unborn children from developing asthma later in life, a U.S. study suggests.

Researchers at Massachusetts General Hospital in Boston used questionnaires to assess vitamin D levels of women when they were pregnant.

They then matched this data with the children who were showing early signs of asthma -- recurrent wheeze -- by the age of 3.

"The higher the maternal level of vitamin D, the lower the child's risk [of asthma]," said Carlos Camargo, lead researcher of the study published in the American Journal of Clinical Nutrition.

Vitamin D is obtained from some foods, including oily fish such as salmon. It is also produced in the skin as a result of exposure to sunlight.

But, during winter months, the sun's rays just aren't strong enough to trigger vitamin D production.

"I think adults in northern latitudes should take vitamin D supplements," Dr. Camargo said in an e-mail.

"The optimal dose is not yet clear, but a recommendation of 800 to 1,000 International Units a day is safe and is known to increase blood levels of vitamin D during these winter months."

Brain cancer therapy

A drug currently used to treat advanced colorectal cancer also seems to slow the growth of deadly brain tumours, a preliminary study suggests.

Avastin is a relatively new type of cancer drug that works by cutting off a tumour's blood supply.

The researchers at Duke University in Durham, N.C., used Avastin, in combination with standard chemotherapy, to treat a small group of patients with brain tumours called gliomas.

The combined treatment halted tumour growth for up to twice as long as the usual therapy, according to the results published in the journal Clinical Cancer Research.

"Though gliomas remain incurable in nearly all cases, the combined drug therapy may buy precious time and preserve physical and mental function longer for patients facing this grim diagnosis," the researchers said in a statement released with the study.

The drug, however, is not cheap. As a result, Avastin has become the centre of a funding controversy in Canada. Only some provinces have agreed to pay for it. In others, patients have been reaching into their pockets to cover the cost. In Saskatchewan, for example, colorectal patients pay about $36,000 for a course of treatment.