A study based on around 40,000 middle-aged Japanese examined dietary, drinking and smoking habits over an 11 year period.
The study shows that the risk of stomach cancer for Japanese men with the lowest salt intake was one in 1000 per year. This doubled to one in 500 among those with the highest salt intake.
For women with a low salt intake the risk was one in 2000 which rose to one in 1300 for those whose diet was high in salt.
Gastric or stomach cancer is the second most frequent cause of cancer deaths world wide with an estimated 776,000 deaths in 1996. It is the fourth most common cancer in the world; in the UK stomach cancer is the sixth most common cancer with 10,000 new cases each year.
Scientists from the National Cancer Centre Research Institute in Kashiwa, near Tokyo, studied questionnaires detailing the diets of men and women in four districts of Japan (Iwate, Akita, Nagano and Okinawa).
Out of 18,684 men studied a total of 358 cases of stomach cancer were reported while 128 cases of the cancer were found in 20,381 women.
Dr Shoichiro Tsugane, who led the study, says: “Although there is a steady decline in its incidence, gastric cancer is still the most common form of cancer in Japan. In addition to salt intake our study also shows that smoking and low consumption of fruit and vegetables increases the risk of stomach cancer particularly in men.”
Scientists know that high salt intake can induce atrophic gastritis which is a precursor to stomach cancer. Salting, pickling and smoking are traditionally popular ways of preparing food in Japan. Pickled vegetable and noodles are rich in sodium and low in vitamin C.
As the Japanese diet has become increasingly westernised there has been a noticeable drop in the rates of stomach cancer but an increase in the rates of brewast and bowel cancers, emphasising the role of diet in the disease.
Dr Tim Key, an epidemiologist for Cancer Research UK which owns the British Journal of Cancer, says: “This study shows strong associations of stomach cancer with the intake of highly salted Japanese foods including salted fish and pickled vegetables. What we don’t know is whether it is specifically the salt in these foods that can cause cancer or a combination of salt and other chemicals.
“In Britain, stomach cancer rates are much lower than in Japan and these types of highly salted foods are not widely consumed. But limiting salt intake is also important for reducing the risk for high blood pressure and cardiovascular disease.”
“The study underlines the importance of limiting salt intake in our daily diet not only to reduce the risk of stomach cancer but also to protect against heart disease.”
- British Journal of Cancer90 (1)
Stomach cancer occurs mostly in older people in the UK with fewer than 10 per cent of cases diagnosed before age 55. Twice as many men suffer from the disease than women. Diet and smoking are both known risk factors.
There has been a dramatic decline in the incidence and mortality of the disease compared to 50 years ago when it was the leading cause of cancer death in Britain. This is due to improved food hygiene and a more balanced diet throughout the year.
Five year survival rates have doubled over the last 25 years in Britain but are still only 11-12 per cent and therefore prevention is important.