We often hear that cancer feeds on sugar, yet some doctors and oncologists brush this idea aside as irrelevant. So, what is the truth and why does it matter?
On the relevance of the question, the answer is quite simple. You cannot treat a disease properly if you don’t understand the cause, because otherwise you are just addressing the symptoms. Like weeds, you have to go after the root to prevent recurrences.
Current Status Quo.
For the last several decades, we have targeted most of our cancer treatments under the assumption that cancer is primarily a genetic disease. The theory goes that when the cell DNA gets damaged by environmental or lifestyle factors, the cell may respond by triggering oncogenes and proliferating without any control.
I have always had my doubt about this theory. Essentially, the main question that is left unanswered is: how come that random mutations in random locations give rise to the same set of cell behaviour everywhere. This set of behaviours are typical hallmark of cancer: uncontrolled and unlimited cell multiplication, avoidance of programmed cell death, creation of blood vessels (angiogenesis) and tissue invasion.
Emergence of a new concept.
Back in 1924, Nobel laureate Otto Warburg formulated the hypothesis that all cancer cells genesis and growth have to rely a lot more than usual on anaerobic glycolysis and lactate fermentation (original paper). In this context, carcinogenesis stems from the lowering of mitochondrial respiration. Warburg regarded the fundamental difference between normal and cancerous cells to be the ratio of glycolysis to respiration; this observation is also known as the Warburg effect.
In layman terms, this means that cancer cells have to rely heavily on splitting glucose (a form of sugar) in the absence of oxygen in order to produce energy. This is hypothesised to be due to a breakdown of the cell’s power plant, known as mitochondria. At this point in time, it is still controversial whether damaged mitochondrial function is a cause or a consequence of cancer, however the fact that the Warburg effect is present in most cancer cells is not contested, and provide both an elegant and simple theory to cancer genesis, which is so far unrivalled by more mainstream theories.
The prime cause of cancer is the replacement of the respiration of oxygen in normal body cells by a fermentation of sugar – Otto Warburg
The case for the theory that damaged mitochondria drive cancer is further strengthened by the fact that, in healthy cells, mitochondria normally drive apoptosis (programmed cell death), which is absent in cancer cells (study). Experiments have also shown that inserting healthy mitochondria into human cancerous cells inhibits cancer cell proliferation and increases the sensitivity to some treatments (study). Electron microscopy imaging of mitochondria from cancer cells have pointed to severe structural changes in the inner membrane of those organelles (study), and other studies have pointed to dysregulation in the lipid metabolism of those membranes (study).
In the last couple of decades, the theory has seen a resurgence in popularity, and gave rise to novel therapeutics intervention (Study).
So, does that mean eating sugar causes cancer?
The “cancer feeds on sugar”, while itself an over-simplification, has led some to believe that eating too much sugar will cause cancer. While there is some truth in this, it is a a bit of an over-statement, and is probably misleading. So, let’s set a few scores:
- An excess of sugar and carbohydrates (grains, pasta, breads, rice, potatoes, fruits, etc) will promote blood sugar dysregulation and hyperinsulinemia, which will increase the risk of cancer (study, study) and other degenerative diseases such as diabetes.
- Even if you eat no sugar and no carbohydrates, your body will make some glucose (a sugar) to sustain itself (a process called gluconeogenesis).
- If you are healthy, fit and insulin sensitive, and eat the occasional sweet, your body is perfectly equipped to handle it.
Now that we have said this, reducing the amount of carbohydrate from something like a “standard diet” to something more reasonable is a great cancer prevention strategy. In fact, many studies have been done and more are on the way to establish the role of carbohydrate restriction and / or the ketogenic diet as an adjuvant strategy in cancer treatment, and they mostly point to improved outcomes and better prognosis (see my previous post on this subject).
While there is little research being made purely on the mechanisms of action of a low-carbohydrate or ketogenic diet on cancer, it stands to reason to believe that a restriction of dietary carbohydrates will mean increased competition for glucose between the cancer and other cells that rely heavily on this for their energy (red blood cells and neurons mainly). It is also unlikely to be the only mechanism of actions here, as such dietary intervention also reduces inflammation, oxidative stress, and stimulates the creation of new mitochondria (source).
How about meat and cancer?
We have all heard the headlines “red meat cause cancer”. If the above is true, how can red meat be a cancer cause?
First, I’d like to say the link between red meat and cancer is a lot weaker than the medias and the world health organisation would have us believe. I would refer you here to this excellent article by Chris Kresser, and this other equally excellent from Dr Jocker but here are the arguments in a nutshell:
- The correlation between red meat and cancer is weak (if at all statistically significant) compared to other known risks such as smoking, asbestos, etc.
- Most of the studies showing a link between meat and cancer suffer from the “healthy user bias”: people who avoid red meat are otherwise more health-conscious than those who don’t.
- You can’t lump in the same category a high-welfare organic grass-fed slice of liver together with a highly-processed, antibiotic-packed, additive-doused hot dog. Yes, they both qualify as red meat, yet one is healthy, the other isn’t. Unfortunately none of those studies control for those parameters.
- Most of the studies making big headlines are done using food recall questionnaire asking people what they ate over the last several years. In other words, the quality of the data is sketchy at best.
- Sensational media headlines purposely confuse relative and absolute risk, as illustrated in the picture below, in order to act as click-bait.
Those considerations aside, there is a good reason to somewhat limit the amount of protein, and muscle meat in particular, if you have or are at risk of cancer: besides glucose, another fuel can be used by cancer cells to fuel their growth. And that is the amino-acid known as glutamine (source). This is a building block for proteins, one of the most common in the body, and of highest concentration in muscle meat.
Addressing the glutamine issue isn’t easy as it is a very important amino acid for the body. Dr Thomas Seyfried is pioneering press-pulse therapies (study) but more research is definitely needed. And don’t forget, proteins in general are critically required by the immune and healing systems, and for muscle mass. Restricting proteins too much can put you at risk of life-threatening cachexia.
Let’s talk about fat.
Over the years, we have seen headlines that cancer may be promoted by a high-fat diet (example). Generally, this type of study has all the flows mentioned above, plus some more. A couple of additional drawbacks are that:
- those studies aren’t controlled for vegetable intake
- the actual composition and rancidity of the fat is often not studied – it would be a totally different story if one would differentiate between “seed oils” extracted at high temperature and cold-pressed vegetable oils with a low content of polyunsaturated oils (see this article for a great explanation, also this one).
In fact, a study has demonstrated that a diet rich in omega-6 can induce mitochondrial damage (study) and lead to cancer (study). Those are typically present in high concentration in oils extracted from seeds such as rapeseed, sunflower oil, cotton seed oil, soybean oil, corn oil and canola oil. I would strongly suggest to avoid any of those as they will increase cancer risk. On the opposite, an increase in omega 3 oil has been found to be protective against cancer (study). Those can be found in wild fish oils and animal fat from grass-fed animals.
Another point to consider is that some pollutants tend to accumulate in fats, and in animal fats in particular. Those pollutants have been shown to induce metabolic syndrome and insulin resistance which are associated with higher cancer risk (great explanation here). Some of them are also known carcinogens. So, the least you can do if you are going to get animal food, is to choose organically-raised animals living in as close to their natural habitat as possible (free to roam on grassland or woodlands, etc). Unfortunately, today “organic” has been already industrialised, so the best thing to do is to form relationships with your local farmers and find those who truly use organic principles in their work.