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Diseases & Conditions

Sugar Causes Cancer


The “sugar causes cancer” myth is popular these days. Cancer is pretty scary to most people. Nobody really wants to get sick with cancer. And we want to have the security of knowing that we can protect ourselves from it.

Thus, the simple claim that sugar causes cancer appeals to us. Because we think, “Gee, I could give up sugar. It would be a noble sacrifice. And then I’d be safe.”

Unfortunately, as we’ll see, it’s simply not true.

Sugar is the current dietary evil. It is enemy no. l, regardless of which dietary camp one belongs to these days. So whenever something gets pinned on sugar, there aren’t many who investigate it further and refute the unfounded claims. Nonetheless, there is no evidence that sugar causes cancer.

It is true that cancer cells use glucose (a sugar) to fuel themselves. Unfortunately, that is hardly enough to indict sugar for causing cancer, because most cells in the body prefer to use glucose as a fuel source. So claiming that sugar causes cancer is either naive or disingenuous. It would be more honest to state that sugar fuels cells. Period.

How does the body obtain glucose? Ideally from food. The body breaks down any digestible carbohydrate and converts it to the usable form of sugar – glucose. So whether you eat a banana, a potato, a piece of sprouted whole wheat bread, a piece of Wonder bread, a Frito, pancakes slathered in maple syrup, Lucky Charms, or a bowl full of white sugar, the carbohydrates get converted to glucose in order to be useable in the body. (Incidentally, I am not suggesting that all of those “foods” have equal nutritional value. I am merely pointing out that in terms of sugar, each is eventually converted to glucose.)

Advocates of the “sugar causes cancer” myth recommend eliminating all sugar from the diet, in order to “starve” cancer. The problem with this is that in order to remove all sugar from the diet, one has to eliminate all digestible carbohydrates, including the much-beloved “healthy” carbohydrates such as carrots, beets, and beans. For low-carbohydrate or zero-carbohydrate advocates, this isn’t a problem. They would love for everyone to stop eating carbohydrates, whether they come from Frosted Flakes or apples. The problem is that eliminating carbohydrates or even drastically reducing them not only starves cancer cells, it starves all cells, including healthy cells.

Once again, low-carb advocates suggest that this is not a problem – that it is, in fact, desirable. But it is not. Despite what the low carb advocates want us to believe—our bodies need glucose. Our bodies will even synthesize glucose if insufficient dietary carbohydrates are eaten. In other words, you absolutely cannot starve cancer cells of glucose while you remain alive since healthy cells and cancer cells alike use glucose.

Also, keep in mind that there are plenty of examples of groups of people eating high carbohydrate diets among which cancer is virtually unheard of. One such striking example is the traditional Kitavan people who have extremely low rates of cancer and yet eat 69 percent of their calories from carbohydrates (Lindeberg, Eliasson, Lindahl, & Ahren, 1999). If eating carbohydrates (sugar) caused cancer, we would expect that groups of people who eat lots of carbohydrates would have higher rates of cancer. But they don’t.

Timothy Moynihan of the Mayo Clinic speculates that the “sugar causes cancer” myth may be due to a misunderstanding of a common medical imaging test for cancer (Moynihan, n.d.). He points out that medical imaging uses radioactive glucose to look for tumors – not because cancer uses glucose preferentially, but because cancer cells use energy faster than healthy cells and thus concentrate any energy source.

Still, many who have an agenda grasp at anything that might support the view that sugar causes cancer. Thus, some claim that “because ketogenic diets cure cancer” we have proof positive that sugar causes cancer.

In the event that you aren’t familiar with ketogenic diets, they are specially designed to deprive the body of carbohydrates and all but the minimum of protein so that the body is forced to use fat as the primary energy source. Some researchers are currently investigating whether ketogenic diets may be an adjunct to conventional cancer treatment (chemotherapy and radiation treatment) (Allen, et al., 2014).

That research suggests that depriving cancer cells of glucose creates additional oxidative stress in cancer cells because using ketones as energy is not as efficient as using sugar. Thus a ketogenic diet produces oxidative stress in all cells, but because cancer cells have faster metabolic rates it creates more oxidative stress more quickly in cancer cells.

There is nothing about that suggesting that sugar causes cancer. All it says is that sugar produces less oxidative stress than ketones, but because cancer cells have higher metabolic rates compared to healthy cells, using ketones in place of sugar is a “hack” that may increase the self-destruction rate of cancer cells faster than the self-destruction rate of healthy cells.

Furthermore, there is no evidence of which I am aware that demonstrates that ketogenic diets can cure cancer. I have seen at least one study that tested the impact of a ketogenic diet on advanced stage cancers (Schmidt, Pfetzer, Schwab, Strauss, & Kämmerer, 2011). Those who were able to successfully remain on the diet for the duration of the study showed mixed outcomes. Some minor positive outcomes were seen, but some problems were also encountered. Overall, the researchers concluded that ketogenic diets may be tolerable for some cancer patients, but nothing indicated that a ketogenic diet offers a miracle cure.

Also consider this: a Johns Hopkins study demonstrated that at least some cancer cells will adapt to use alternative fuel sources in the absence of glucose (Le, et al., 2013). Despite the apparent fact that cancer cells cannot use ketones as fuel, they are adapted to be able to use amino acids such as glutamine as an energy


source. The implication is that in order to successfully “starve” cancer cells, one would have to not only eliminate all dietary carbohydrates, but also all dietary protein. Of course, the body would then begin to catabolize muscle and eventually even organs in order to meet its protein needs, which would inevitably feed cancer cells as well as other cells in the body. So this strategy of “starving” cancer cells is more likely to starve the person before it starves the cancer.

In conclusion, the claim that sugar causes cancer is completely unfounded. Sugar and carbohydrates in general appear to be an essential part of the human diet in most cases, and restricting them to “starve” cancer is misguided and potentially harmful.