Dana at Hold the Toast has several articles on the problems with fructose, including the hidden fructose in Agave Nectar. Her latest post repeats the wide-spread media analysis of a recent study where fructose shows itself to be a superior fuel for pancreatic cancer cells. Unlike most of the media accounts, Dana focuses on the important part of the story:
It was the first sentence in the abstract that really caught my eye: Carbohydrate metabolism via glycolysis and the tricarboxylic acid cycle is pivotal for cancer growth, and increased refined carbohydrate consumption adversely affects cancer survival. Got that? Carbohydrates are pivotal for cancer growth. Eating carbs means you’re less likely to survive cancer. Remember that next time someone tells you you’re courting cancer by eating meat and eggs instead of grains and fruit.
Unlike some reports in the press and blogosphere elsewhere, the study doesn’t show that fructose causes pancreatic cancer or feeds cancer cells in the body. The researchers used pancreatic cancer cells for the test, isolated in petri dishes, and then added more glucose or fructose to the solutions. They were then able to measure the rate at which the cells divided and grew, and found that:
In comparison with glucose, fructose induces thiamine-dependent transketolase flux and is preferentially metabolized via the nonoxidative pentose phosphate pathway to synthesize nucleic acids and increase uric acid production.
Ah. I always suspected fructose was preferentially metabolized via the nonoxidative pentose phosphate pathway. I’ll have to have biologist or doctor sort out that sentence for me.
My understanding of the way fructose is metabolized by the liver leads me to believe a cancer cell in your pancreas would never see fructose. It would see glucose in the blood stream, which it uses to divide and grow just fine. Dr. Briffa explains:
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.
Those wanting to read more about fructose can follow this MegaSearch Link for all the articles by our Low Carb Daily index of websites. We select only low carb / paleo / primal sites for this search, targeting the results to the interests of our readers.
I am as eager as the next low carber to pounce on a media story that equates fructose with cancer, but let’s be honest: this study doesn’t say that. We have a duty to try and report things accurately, although for us laypeople, it can be difficult. Remember, we are critical of the old idea that eating cholesterol added cholesterol to the bloodstream. It makes sense on one level, and that would be great, except it simply isn’t true. We know that now. Why are we so quick to say eating sugar feeds cancer? We need our theory validated with research.
On the other side, the Corn Refiner’s Association (CRA) has already weighed in with a critique of the study, so the battle is engaged. And you know what? Some of their criticisms are valid.
Dietary science is the bastard son of real science, yet the mass media treats every new study like it’s E=MC2.
As Dana pointed out, the real problem is that cancer cells use glucose, and a high blood glucose level may assist in their growth. And carbs lead to high blood glucose levels. It sounds reasonable that a low carb diet would help slow cancer growth, but are there any studies showing that effect?
Well, the University of Würzburg Hospital has recommended a low carb, ketogenic diet for cancer patients since 2007. And they link a few studies on their site.
At least one other study shows that starving cancer with a very low calorie, ketogenic diet may work. This isn’t the type of diet we are on: calories were limited to 600 per day, and the ratio of fat to carbs and protein was 4:1. Italian and American researchers used this extreme, ketogenic diet and traditional treatments (radiation and chemotherapy) and mapped the progress of a particularly bad cancer: glioblastoma multiforme (brain cancer):
After two months treatment, the patient’s body weight was reduced by about 20% and no discernable brain tumor tissue was detected using either FDG-PET or MRI imaging. Biomarker changes showed reduced levels of blood glucose and elevated levels of urinary ketones. MRI evidence of tumor recurrence was found 10 weeks after suspension of strict diet therapy.
This is one study, on one patient, with a very strict dietary regime that showed promise. It doesn’t mean that staying in ketosis prevents cancer, or that a different type of cancer would be slowed by the same ketogenic diet. It does point out the need for further research.
Needless to say, someone with cancer would want to discuss this approach with their doctor as an adjunct to standard treatment, and not risk “going it alone” based on this one study.