Smoking cigarettes cuts an average of 10 years off a person’s life, a landmark study suggests. But it also shows that quitting at any age reduces the risks of dying from smoking-related diseases. The findings, published in the British Medical Journal, are the culmination of a 50-year study involving 34,439 men. The study, which began in 1951, was the first to confirm the link between smoking and lung cancer exactly 50 years ago. All of those involved in the study were born between 1900 and 1930 and all worked as doctors.

They were each asked about their smoking habits at the start of the study in 1951. Researchers contacted them periodically over the next 50 years to see if those habits had changed. Since the study began in 1951, tobacco has killed around 100 million people Professor Alex Markham, Cancer Research UK They also gathered information on those who died during the period. They have now analysed that data. They found that men who have never smoked lived on average 10 years longer than those who smoked for most of their lives. Men who smoked were at least twice as likely to die before the age of 70 as non-smokers. They were up to three times more likely to die before they were 90 compared to those who never took up the habit. The average age of these men when they started smoking was 18. On average, they said they smoked around 18 cigarettes a day.

It was already known that about half of all persistent cigarette smokers are killed by their habit, a quarter while still in middle age (35-69 years). The biggest killers are cancer, heart disease and stroke. But the study also revealed that giving up cigarettes at any age has major health benefits. It found that men who had stopped smoking by the time they were 30 lived as long as those who never smoked. Those who quit at 40, lived just one year less than those who had never smoked. Those who stopped smoking at 50 added six years onto their lives, while those who kicked the habit at 60 added an extra three years to their life.

Arylamines are known bladder carcinogens and are an important constituent of tobacco smoke. The handling of arylamines in the body is complex and includes metabolism by NAT1 and NAT2, enzymes that play a role in both activation and detoxification of arylamines and their congeners. Both NAT1 and NAT2 are polymorphic, with alleles that have been shown to correlate with higher or lower enzyme activity. To explore the combined role of these genes and exposure on bladder cancer risk, we examined the NAT1 and NAT2 genotype in a case-control study of bladder cancer in which detailed exposure histories were available on all 230 cases and 203 frequency-matched controls. Using PCR-RFLP genotyping, we determined NAT2 genotype for the five most common alleles, NAT2*4, NAT2*5, NAT2*6, NAT2*7, NAT2*14 (frequently referred to as WT, M1, M2, M3, and M4, respectively).

Similarly, the NAT1 genotype was determined for the four most common alleles NAT1*3, NAT1*4, and NAT1*11, and the putative high-activity allele, NAT1*10. No association between NAT2 genotype and bladder cancer risk was found whether genotype was considered alone or in combination with smoking, in either stratified or logistic regression analysis that adjusted for age, sex, and race. Stratified and logistic regression analysis both demonstrated an increased risk for individuals carrying the NAT1*10 allele among smokers. There was evidence of a gene-dosage effect, such that those who were homozygous for the NAT1*10 allele had the highest risks.

There was also evidence of a statistically significant gene-environment interaction, such that bladder cancer risk depends on both NAT1 genotype and smoking exposure. Interestingly, although NAT2 genotype did not influence risk either alone or in combination with smoking exposure, there was evidence of a statistically significant gene-gene-environment three-way interaction. Bladder cancer risk from smoking exposure is particularly high in those who inherit NAT2 slow alleles in combination with one or two copies of the NAT1*10 allele. A biological mechanism for this finding is suggested.

Consuming large amounts of milk may increase the risk of developing ovarian cancer, research suggests. A study of more than 60,000 women found drinking more than two glasses of milk a day significantly upped the risk of the most serious form of the disease. Dairy products have previously been linked to cancers, including those of the breast and prostate. The research, by Sweden’s Karolinska Institute, is published in the American Journal of Clinical Nutrition. The researchers followed 61,084 women aged 38 to 76 for around 13 years. During this time a total of 266 women were diagnosed with ovarian cancer, of whom 125 had serious ovarian cancer.

The researchers found women who consumed more than four servings of dairy products a day had twice the risk of serious ovarian cancer than women who had fewer than two. They found that milk had the strongest link with ovarian cancer – those women who drank two or more glasses a day were at double the risk of those who did not consume it at all, or only in small amounts. The reason why milk may increase the risk of ovarian cancer is unclear, but one theory is that lactose, a type of sugar found in milk, may overstimulate production of hormones which encourage tumour growth. Dr Kate Law, of Cancer Research UK, said it was not yet clear how nutrients, or the amount and distribution of body fat affected the risk of developing cancer. She said: “Previous research has also suggested that a diet rich in whole milk, yogurt and cheese may put women at higher risk of ovarian cancer.

“But the picture is far from clear, as other evidence suggests that women who drink skimmed or low-fat milk might have a lower risk of ovarian cancer.” Dr Law a major study, involving 500,000 people, was currently underway to try to assess the impact on diet on cancer. “Until more is known about the specific components of diet that influence cancer risk, the best advice is to emphasize a balanced diet which includes plenty of fresh fruit and vegetables.” Around 6,700 women in the UK are diagnosed with ovarian cancer each year.

Researchers at the London Health Sciences Centre and London Regional Cancer Centre are looking for more than 3,000 men to test whether dietary supplements help prevent the disease. “Even (if the supplements have) a small effect (it) will translate into big results because this is such a common problem,” says Dr. John Radwan, a radiation oncologist at London Health Sciences Centre. London is one of eight Canadian cities participating in the 400-city study, the largest of its kind, with 32,000 participants drawn from Canada, the United States and Puerto Rico. Spearheaded by the National Cancer Institute and the Southwest Oncology Group, the study shows a new attitude toward alternative medicine, says Nancy Pus, research co-ordinator for the department of urology at London Health Sciences Centre. “The medical community is looking more at alternative therapies and the role of vitamins and nutrients in preventing diseases,” she says. Eighty per cent of Radwan’s patients are victims of prostate cancer. Prostate cancer is the second most deadly form of the disease next to lung cancer. One in every eight Canadian men will develop the disease. Dubbed SELECT, (Selenium and Vitamin E Cancer Prevention Trial) the study tests the effects of selenium and vitamin E. Both elements are found naturally in food. Researchers aren’t sure the supplements will work, but men should still get them, says John Blanchard, president of the Prostate Cancer Research Foundation of Canada. “Men ought to take some action, rather than saying the jury’s out. Within reason, (these supplements) can’t hurt you . . . we’re not talking about some dangerous medication here,” he says.

Vitamin E and selenium are both known antioxidants. Some doctors say they neutralize cancer-causing toxins that damage the genetic material of cells. Radwan says they definitely can’t hurt. “It seems to be a win-win situation, with antioxidants. They can only make things better,” he says. He advises individuals with high blood pressure to stay away from vitamin E, because it can thin the blood. Others excluded from the study are those who had cancer in the last five years, excluding non-melanoma skin cancer. Participants must be over age 55, if white, and 50 or older, if black. Radwan explained blacks are more susceptible to the disease, although it’s not yet known why. Study participants will take two capsules per day — a combination of either small doses of the supplements or placebos.

Participants will be tracked for seven years each — meaning the study could take up to 12 years to complete if recruitment takes an estimated five years. Radwan urges men at high risk — those with a family history of the disease — to seriously consider getting involved. The push for the study evolved from testing the supplements to see if they prevented other forms of cancer. In the case of a 1998 trial of vitamin E on 29,000 Finnish men, the supplement failed to prevent heavy smokers from developing lung cancer. Nonetheless, the clinical trial was successful in reducing the risk of prostate cancer among the heavy-smoking population by 32 per cent, Radwan said.