Cancer, in essence, is a condition caused by cells dividing more rapidly than they should to form a clump of abnormal cells. Lots of things appear to have the capacity to trigger cancerous change in cells (some chemicals, free radical damage, radiation, for example), but once cancerous cells form, they still need feeding to survive. Cancerous tumour can develop their own blood supply, through which they can be fed vital nutrients to stay alive and proliferate.
It has been long recognised that cancerous cells tend to do well when fed glucose – a key fuel in the bloodstream. One might argue then that, as much as possible, it makes sense for those with cancer to avoid consuming foods that cause gluts of sugar in the blood stream such as sugary foods and starchy carbohydrates such as bread, potatoes, rice, pasta and many breakfast cereals.
I was interested this week to read about a study which assessed the effect of not glucose, but fructose, on cancer cell growth [1]. Fructose is found naturally in fruits and vegetables, and it also makes up half of sucrose (table sugar) – the other half being glucose. And last, but by no means least, fructose can be found in ‘high fructose corn syrup’ (HFCS), which over the last couple of decades has increasingly pervaded the Western diet.
Fructose has, until relatively recently, enjoyed a ‘healthy’ reputation on the basis that it does not lead to spikes in blood sugar. It’s been particularly recommended for diabetics for this reason. However, it turns out that fructose has the potential for quite toxic effects in the body. See here, here, here and here for some recent posts about this.
Back to cancer…
The study in question found, in summary, that feeding cancer cells fructose caused them to proliferate. Obviously, this is not a good state of affairs. The authors of the study suggest that reducing intake of refined fructose may disrupt cancer growth.
When fructose is consumed it travels to the liver. The vast majority, if not all, of it is metabolised in the liver, meaning that little or any reaches the general circulation. However, there is always the potential that uric acid might exert a considerable direct effect on the liver. We can perhaps see the potential for fructose to be directly toxic to the liver in some evidence linking its consumption with ‘fatty liver’ (a build-up of fat within the tissue of the liver).
But what about other tissues in the body?
One of the effects of fructose is to cause a ramping up of uric acid in the liver. Uric acid is, as its name suggests, acidic. And the relevance of this is that some cancer cells grow better in an acidic environment. Now, the body has processes by which it regulates the pH (acidity/alkalinity) of the bloodstream within quite a narrow range. However, there is the potential for the pH to drop (become more acidic) and this might perhaps encourage cancer growth.
I’m not aware of any evidence linking fructose consumption and cancer in the scientific literature. However, this recent study, I think, gives us another potential reason for giving fructose and high fructose corn syrup a miss.
References:
1. Liu H, et al. Fructose induces tranketolase flux to promote pancreatic cancer growth. Cancer Research 2010;70(15):6368-76
And to think how all those detox books and ‘how to recover from a hangover’ articles claim fruit to be detoxifying.
Bruce Forsyth, mind you, has made it to 82 (I think), and a recent documentary following around showed him eating porridge with soy milk for breakfast, with blueberries carefully placed on top and “fruit sugar” as he said, sprinkled on that. Clearly advised by someone like G. McKeith, wonder how long he’s been eating that way…
I think it is wrong to flatter fructose, HFCS and white sugar (and for that matter all refined and processed ‘foods’) with the name food – in reality the best that they can be described as (euphemistically)is food extracts. Foods are complex highly ordered, low entropy substances which are GROWN, by nature, and get their low entropy from sunlight (or more accurately the contrast between sunlight and the coldness of deep space) and this low entropy is transferred to animals, such as us, when we eat natural food so that our bodies are maintained in a highly ordered, low entropy, healthy state. In contrast substances such as fructose and HFCS are isolated chemicals extracted, usually from corn – it is completely pointless to eat them as they have no nutritional benefits, unlike the natural foods from which they are extracted. Note that though it is relatively easy to extract fructose from natural foods, it is completely impossible to reconstruct natural foods from fructose and other ‘components’. Natural foods including vegetables and fruits, from which fructose can be extracted, have sustained healthy human populations for millenia and are completely familiar to our DNA. In contrast the isolated extracts are unfamiliar to our DNA with risk of causing inflammation and disease. It is an absolute ‘no brainer’ that one should eat (all) natural foods but completely avoid fructose and HFCS – why on earth would anyone want to eat them ?
Another recent study looking at fructose and breast cancer:
Monzavi-Karbassi B et al. 2010. Fructose as a carbon source induces an aggressive phenotype in MDA-MB-468 breast tumor cells. Int J Oncol. 37(3):615-22.
Abstract:
Aberrant glycosylation is a universal feature of cancer cells, and certain glycan structures are well-known markers for tumor progression. Availability and composition of sugars in the microenvironment may affect cell glycosylation. Recent studies of human breast tumor cell lines indicate their ability to take up and utilize fructose. Here we tested the hypothesis that adding fructose to culture as a carbon source induces phenotypic changes in cultured human breast tumor cells that are associated with metastatic disease. MDA-MB-468 cells were adapted to culture media in which fructose was substituted for glucose. Changes in cell surface glycan structures, expression of genes related to glycan assembly, cytoskeleton F-actin, migration, adhesion and invasion were determined. Cells cultured in fructose expressed distinct cell-surface glycans. The addition of fructose affected sialylation and fucosylation patterns. Fructose feeding also increased binding of leukoagglutinating Phaseolus vulgaris isolectin, suggesting a possible rise in expression of branching beta-1, 6 GlcNAc structures. Rhodamine-phalloidin staining revealed an altered F-actin cytoskeletal system. Fructose accelerated cellular migration and increased invasion. These data suggest that changing the carbon source of the less aggressive MDA-MB-468 cell line induced characteristics associated with more aggressive phenotypes. These data could be of fundamental importance due to the markedly increased consumption of sweeteners containing free fructose in recent years, as they suggest that the presence of fructose in nutritional microenvironment of tumor cells may negatively affect the outcome for some breast cancer patients.
You write “The authors of the study suggest that reducing intake of refined fructose may disrupt cancer growth.” I assume that means fruit is fine?
Ed
Yes, I think so.
This video is well worth sitting through – really thought-provoking:
Robert H. Lustig, MD, UCSF Professor of Pediatrics, Division of Endocrinology explores the damage caused by sugary foods and explains why fructose is actually one of the worst culprits in obesity despite its ‘natural’ and ‘healthy’ reputation.
http://www.youtube.com/watch?v=dBnniua6-oM
Is there any truth to the claim that fructose does not raise or spike blood sugar?
I can’t imagine drinking orange juice would be any different than drinking a coke.
As I understand it fructose is metabolised in the liver – excess can cause fatty liver in the same wasy as alcohol does – so it doesn’t spike blood sugar in the same way as glucose does
tomorrow i’ll juice 2 fresh apples (fructose) first thing in the morning, and then measure my blood sugar to find the peak.
then i’ll repeat the next day, juicing 2 fresh beets (sucrose).
I’ll make sure the amount of juice is the same, but since sucrose = glucose + fructose, i can’t see how the body just wouldn’t break it down and treat all sugars the same!
btw, regarding the cancer connection:
http://www.boingboing.net/2010/08/08/nope-high-fructose-c.html
Isolated fructose does not contain any nutrients that the body needs to maintain its immunity to defend against cancer and other diseases. Isolated fructose probably does not directly cause cancer any more than any other empty calorie foods – but if one eats large amounts of empty calorie foods rather than nutritious foods (ie a wide range of unprocessed, natural , whole foods) one’s immunity will be compromised and cancer risk increased.
Are you saying we can’t eat much fruit?