Well, I am about half-way through my certificate programme in Plant-Based Nutrition with eCornell. It has been a fascinating journey so far. I thought I would write lots of blog posts as I worked through the material, but I’m afraid it has been as much as I can manage just to keep up with it all. I will write about it all later of course, don’t worry.
Today we have been asked, as an exercise, to write a letter to a friend with a family history of cancer who is concerned about their own risk of developing the disease. Also today I notice that many of my Facebook friends are busy posting photographs of themselves without make-up all over the internet in an effort to promote cancer awareness…
So today I am posting a copy of my letter here, as my contribution to the effort to promote cancer awareness. Please read it – it’s really important stuff…
A little bird told me that you are worried about your risk of developing cancer. As you know I am studying plant-based nutrition with eCornell, and I am learning some interesting things about cancer and it’s relationship with the food we eat. I hope you won’t mind if I share some of them with you.
I would like to begin with some basic biology. Cancer develops in three stages: initiation is the process in which DNA is damaged by some external agent (a carcinogen) such as a chemical, a virus or radiation. Most of this damage is repaired by the body, but occasionally it isn’t. If the damage to the DNA sequence is passed on to the following generations of cells then an irreversible mutation is said to have occurred. Sometimes mutations are inherited and these cases give rise to a “genetic predisposition to cancer”. However not all mutations go on to result in cancer, because two more stages need to occur in order for manifest disease to develop. Promotion is the process by which these damaged daughter cells proliferate to produce small clusters known as foci. Progression is the process by which foci grow and metastasise around the body, producing tumours – or cancer as we know it.
In the 1960’s and 70’s a story began to emerge around the potential role of dietary protein in cancer promotion in particular. It was observed that children in the Philippines, who ate higher amounts of protein, generally those living in more affluent areas, had higher rates of liver cancer. At about the same time scientists in India published the results of an experiment in which rats that had been exposed to the potent carcinogen aflatoxin were fed diets containing either 5% or 20% casein (the main protein found in cow’s milk). All the animals fed the 20% casein diet went on to develop tumours, while none of those fed the 5% casein diet did. This marked effect has been confirmed in repeated studies in different laboratories around the world. It was later shown that switching rats from high to low casein diets could switch off tumour development, and vice versa. In another study animals fed the two diets were followed for the duration of their natural lifespan. At 100 weeks of age all the rats consuming the low protein diet were alive, while all those consuming the high protein diet were dead. A similar effect has also been shown in transgenic mice transfected with the hepatitis B virus, and in promoting mammary (breast) cancer in rats exposed to two other experimental carcinogens.
The percentage of dietary casein required to stimulate the growth of tumour cell clusters was found to be about 10%. Interestingly the recommended daily amount of dietary protein for human beings works out as between 8 and 10% of total calories. This is not an arbitrary figure but is derived from nitrogen balance studies carried out to determine exactly how much protein our bodies need. However most people consuming a standard western diet consume between 11% and 22% of their total calories from protein. Most of this protein is derived from animal sources, as we have been led to believe for many years in the West that meat and dairy products are necessary sources of complete protein for human beings. However it is interesting to observe that wheat and soy proteins did not produce the same cancer promoting effect in laboratory animals. Wheat and soy proteins are incomplete proteins, which means they do not by themselves contain all the essential amino acids required for human tissue growth and repair. However when the missing amino acids were artificially added to the animals’ feeds to make them complete, wheat and soy proteins acted in the same way as casein. This suggests that complete proteins, far from being the healthy proteins our bodies need, are actually harmful and cause cancer to develop where it might otherwise not have done, even in the presence of an underlying mutation.
Meanwhile it is easily possible to obtain 8-10% of our total calories from the proteins found in whole plant foods. All plant foods contain protein: 20% of the calories in broccoli are derived from protein, 31% in spinach, 18% in chickpeas, 23% in peas, 15% in wild rice. You get the idea. Most fruits come in at less than 10%, so if you eat a varied whole-food, plant-based diet you will naturally take in protein in the optimal range and what is more, it will be healthy, non-tumour promoting protein.
Well, you might ask how we can be so sure that studies carried out in rats and mice apply to humans. This would be a reasonable question. How can we find out if this situation also occurs in human beings? We could conduct rigorous dietary intervention studies with cancer patients, randomizing them to either their normal diet or a low (<5% of total calories) protein diet and see how they get on. So far, nearly fifty years on from the original finding, to my knowledge and despite the millions of pounds spent annually on cancer research, this relatively simple experiment has not been done.
While we can debate the reasons for this and await further research, there are some other clues to help us in the mean time. Rates of cancer in populations traditionally consuming whole-food plant-based diets, such as breast cancer in traditional rural Chinese women for example, are much lower than they are in the West, while those migrating from these areas to more affluent cities or countries where meat and dairy consumption are prevalent see their risk of cancer rise significantly within two generations. This suggests a primarily environmental cause for most of the cancers prevalent in the West today. There are also many, many anecdotal stories of individuals improving their cancer outcomes by changing their diet in the direction of more whole plant foods and less animal-based foods and refined and processed products. Plant foods of course contain thousands of phytonutrients, antioxidants, vitamins and minerals that all act together in symphony to bring about health and combat disease. We do not at the present time know what these all are, but few experts debate the importance of a diet high in fruits and vegetables to reduce cancer risk. My contention is that a diet consisting entirely of fruits, vegetables and other whole plant foods such as nuts, seeds, grains and legumes, without any harmful animal-based foods at all, offers human beings the best hope for good health and a long life free of cancer and other chronic diseases that are causing so much suffering in our society today. We can take control of our own destiny in this way.
[N.B. For more information, or the original references, please see The China Study by T. Colin Campbell and Thomas M. Campbell (BenBella Books 2006)]