Diabetes and cancer are two common diseases with a strong impact on health across the globe. Epidemiologic evidence suggests that diabetics are at higher risk for certain forms of cancer. Especially Type 2 Diabetes and Cancer share many risk factors. Dr Vedavati Purandare explores the links between the two ailments.
When you hear of a loved one being diagnosed with Cancer, your first thought might be that the person has perhaps not very long to live. You think of life long suffering and pain, or at best a pitiable existence. On the other hand, when you hear of someone suffering of Diabetes, the news may not evoke such strong emotions, even though both diseases – Diabetes and Cancer are potentially life-threatening.
Both diseases have one thing in common – like many medical conditions, early diagnosis gives you a better shot at survival and a long, healthy life. Also, a positive attitude and rigorously controlled lifestyle become part of every prescription – whether it is to keep your Diabetes under control, or to starve the Cancer cells to stunt growth and prevent the tumour from progressing quickly. What you may not have known is that there are a lot more factors that connect these two seemingly different diseases.
Lack of awareness
A major concern in the Indian scenario is the lack of awareness and knowledge on Diabetes. Just like cancer, Diabetes cannot be seen and in many cases have been developing and growing in your body for years without detection. Most people treat Diabetes as a mild illness and fail to take care of it until it’s too late. Thus often the two diseases are called ‘Silent killers’.
The two diseases also share certain risk factors, of which we cannot control certain factors such as age, family history and ethnicity. However, some risk factors like obesity, sedentary lifestyle, unhealthy diet and smoking also make you more vulnerable to diseases, and these can be controlled through well-timed intervention.
Cancer on the body
In cancer’s grip, the whole body is at war. Cancer cells really do act like armed bandits, roving outside the law. They are unhindered by any of the restraints a healthy body respects. With their abnormal genes, they escape; they lose the obligation to die after a certain number of divisions. They become immortal. They ignore signals from surrounding tissues – alarmed by the overcrowding – that tell them to stop multiplying. Still worse, they poison these tissues with the particular substance they secrete. These poisons create a local inflammation that stimulates the cancerous expansion even more, at the expense of neighbouring territories.
No living cell can survive if it isn’t in contact with tiny blood vessels, filaments as fine as a human hair, called capillaries bring the oxygen and nutrients needed by cells and carry away waste from the cellular metabolism. Cancer cells must also have nourishment imported and waste exported. To survive, tumours thus need to be deeply infiltrated with capillaries. But since tumours grow at high speed, new blood vessels must be made to sprout quickly. This phenomenon has been named as ‘angiogenesis’ from the Greek ‘angio’ for vessel and ‘genesis’ for birth.
There are certain circumstances under which these savage bands are disrupted and lose their virulence:
- when the immune system mobilises against them
- when the body refuses to create the inflammation without which they can neither grow, nor invade new territories
- when blood vessels refuse to reproduce and provide the supplies they need to grow.
These are the mechanisms that can be reinforced to prevent the disease from taking hold. Once a tumour is installed, none of these natural defences can replace chemotherapy or radiotherapy. But they can be exploited, alongside conventional treatments, to fully mobilise the body’s resistance to cancer.
So what‘s the link ?
An association between Diabetes and Cancer has been talked about for several years, but it is only in the recent past (about 10 years) that significant evidence has established the link between the two and has proved that insulin plays a crucial role here.
56% of our calories come from three sources that were non-existent when our genes were developing:
- Refined sugars (cane and beet sugar, corn, syrup, fructose, etc)
- Bleached flour (white bread, white pasts, white rice, etc)
- Vegetable oils (soybean, sunflower, corn, trans fats)
It so happens that these three sources contain none of the proteins, vitamins, or omega-3 fatty acids needed to keep our bodies functioning. On the other hand they directly fuel the growth of cancer. When we eat sugar or white flour – foods with a high glycemic index – blood levels of glucose rise rapidly. The body immediately releases a dose of insulin to enable the glucose to enter cells. The secretion of insulin is accompanied by the release of another molecule called IGF (insulin-like growth factor) whose role is to stimulate cell growth. In short, sugar nourishes tissues and makes them grow faster. Furthermore, insulin and IGF have another effect in common: they promote the factors of inflammation which also stimulates cell growth and acts in turn as fertiliser for tumours.
There is good reason to believe the sugar boom contributes to the cancer epidemic, as it is linked to an explosion off insulin and IGF in our bodies.
Type 2 Diabetes and risk of Cancer
The body of Type 2 Diabetics cannot make efficient use of the insulin – a condition known as insulin resistance. To compensate, the pancreas speeds up the production of insulin in your body. Consequently, insulin begins to build up in your blood stream, which causes cells to divide, grow and spread – this may include cancerous cells, leading to growth of the tumour. Those with Type 1 Diabetes have no insulin production at all, and depend on artificially injected insulin, which can be more precisely controlled.
Studies suggest that people with Diabetes (primarily Type 2) are associated with an increased risk of some cancers such as liver, pancreas, colon/rectum, breast, and bladder cancers. Therefore, it is very important that you monitor and keep your blood sugar levels regulated. On the other hand, Diabetes is also associated with a reduced risk for prostate cancer.
Some recent studies have also shown certain treatment methods for Diabetes to be associated with Cancer. There is evidence to suggest that Metformin, a popular drug for blood glucose control, is associated with a lower risk of cancer against external insulin which is thought to increase the risk of cancer (but whether insulin glargine or other types of insulin are a cause for concern, remains unclear).
This may put in perspective the need to religiously monitor and control your blood glucose levels. On one hand you are containing at least one of the factors that may feed the dangerous cancer cells. At the same time, in case of Type 2 Diabetes, rigorous control helps avoid or delay the need for external insulin, which in turn is another risk factor for cancerous growth. Hence the golden standard – eat healthy, exercise regularly, always take your medication on time, monitor your blood glucose levels and go for the recommended health screening – could yield unseen benefits for your health in warding off even bigger demons. Screening early is very important, as early detection means early intervention, which drastically improves your chances of survival. Patients with diabetes should be strongly encouraged by their health care professionals to undergo appropriate cancer screenings as recommended for all people in their age and sex.