There are 2 types of diabetes mellitus – Type I and Type II. Type I diabetes occurs when the pancreatic islets, which produce insulin, are destroyed by an auto-immune process. It affects young children and they are dependent on insulin injections for life. Type II diabetes occurs when the body tissue becomes less sensitive to the action of insulin, thus, more insulin has to be produced by the body in order to keep the glucose level normal. Type II diabetes usually affects adults who are overweight / obese and older. As one gets fatter, one develops insulin resistance and this leads to an impaired glucose level. Eventually a proportion of overweight / obese people develop persistently elevated glucose levels and the condition is termed Type II diabetes.

Researcher in Umea University, Sweden, studied the association between blood glucose and cancer risk in 274,126 men and 275,818 women from Norway, Austria and Sweden (PLoS Med 2009; 6(12): e1000201). The study found that impaired glucose level was associated with increased incident and fatal cancer risk. In men, the risk per 1 mmol/L glucose increment for incident cancer and fatal cancer was increased by 5% and 15%, respectively. Significant increase in the risk of incident and fatal site-specific cancer was observed for cancer of the liver, gallbladder and the respiratory tract. Incident risk of cancer of the thyroid and multiple myeloma were increased. Men with the highest impaired glucose level also had significant increased risk of fatal colon cancer. In women, the risk for incident cancer and fatal cancer was increased by 11% and 21% respectively. Significant increase in the risk of incident and fatal site-specific cancer was observed for cancer of the pancreas and stomach. Incident risk of urinary bladder cancer was increased. Women with the most amount of impaired glucose level also had significant increased risk of incident endometrial cancer.

The result from this European study corroborates the findings of a Korean study published in 2005. Impaired glucose levels are associated with increased risk of cancer. For those who are overweight, this bit of information is another reason for you to lose weight. Achieving it depends on what you eat, how much exercise you do and how determined you are.

Not infrequently, I have had patients who asked “Can I have this operation later?” after being told that they have a tumour in their liver or colon. My usual first response is “Sooner rather than later. A delay of a few weeks may be alright but not a few months.” As any operation has its attendant mortality risk, it is reasonable for a patient to want some time in order to think things over or to sort out a few things at work and / or at home before undergoing the procedure. So how much delay is acceptable? Is there a critical cut off time for treating cancer?

Researchers from the Aarhus University Hospital in Denmark studied 740 patients diagnosed with colorectal cancer (Br J Surg 2009; 96: 1183 – 1189). There were 458 patients with colonic cancer and 282 rectal cancer patients. The researchers were examining the association between therapeutic delay and survival. Three types of delay were studied: total therapeutic delay – the interval from symptom onset to treatment initiation; provider delay – the interval from first physician contact until treatment initiation and hospital delay – the interval from referral to a hospital until treatment initiation. In colonic cancer patients, the median total therapeutic delay (116 days), provider delay (52 days) and hospital delay (28 days) had no impact on survival in the 458 patients. However, in the rectal cancer group, the study found that a total therapeutic delay of 60 days or more was associated with a 69% increased risk of mortality. In this group, the median total therapeutic delay was 134 days, 49 days for provider delay and the hospital delay was 28 days. The study also found that provider and hospital delay had no impact on the survival of rectal cancer patients. The study showed that early diagnosis of rectal cancer has a significant impact on survival. The longest delay was patient delay – due to non-recognition of symptoms and presenting to the general practitioner late.

The above study highlights the importance of receiving prompt treatment after the onset of symptoms in order to reduce the risk of dying. One cannot find a “Time-table of acceptable delays in initiating treatment” for the different type of cancers. I believe most doctors will adhere to the principle of “Sooner rather than later” when it comes to treating an illness. I strongly urge all patients to subscribe to the same principle too.

Recently the wife of a patient of mine asked “Can he eat beef?”  It transpires that the daughter and son-in-law have told the patient that he is not allowed to eat beef as it will make his cancer worst and beef causes cancer. I have been asked the same question by quite a number of patients. Is cancer caused by eating beef?

A recent study from the National Cancer Institute examined the associations between meat consumption (type of meat, cooking methods and related mutagens), heme iron, nitrite / nitrate and prostate cancer in 175,343 US men aged between 50 and 71 years of age (Am J Epidemiol 2009; 170: 1165 – 1177). These men were followed up for 9 years. The study showed that men who ate the most versus those who ate the least amount of red meat had a 12% higher risk of developing prostate cancer. For processed meat, the risk was 7%. The study also found that heme iron, barbequed/ grilled meat and benzo[a]pyrene were all associated with increased risk of prostate cancer. Nitrite and nitrate intakes were associated with increased risk of advanced prostate cancer.

In certain parts of China, the incidence of cancers of the oesophagus and stomach are much higher than the national average. Detailed studies finally showed that this was related to the pickled vegetables in their diet. The pickled vegetables contained significant amounts of nitrite and nitrate which are known to be carcinogenic. Recent studies have also shown that individuals who drink very hot tea have a higher incidence of cancer of the oesophagus. The likely mechanism here is related to the heat rather than the tea itself.

Cooking certain meats at high temperatures creates chemicals that are not present in uncooked meats. Heterocyclic amines (HCAs) are a group of chemical compounds formed from the cooking of muscle meats such as beef, pork, fowl and fish. HCAs form when amino acids (the building blocks of proteins) and creatine (a chemical in muscles) react at high temperatures during cooking. HCAs are potent compounds that can cause cells to mutate and in experimental animal models HCAs have been shown to induce tumours. Temperature is the most important factor in the formation of HCAs. Frying, barbecuing and broiling involve cooking at very high temperatures and thus produce the largest amounts of HCAs. Baking and oven roasting lead to lower levels of HCAs as the cooking temperature is lower. Poaching, stewing and boiling produce negligible amounts of HCAs. When meat is microwaved for 2 minutes before cooking, the HCA content is reduced by 90%.

From the examples given above, would it be correct to stop drinking tea because drinking hot tea has been shown to be associated with an increased risk of developing oesophageal cancer? Similarly, should one stop eating vegetables because pickled vegetables have been associated with increased risk of developing oesophageal and stomach cancers?

Association is not causation. Furthermore, the reasons behind an association may be due to factors other than the starting ingredient, such as beef. The reason for the association may be because of what you have done to the ingredient.