Rethinking “Sugar Feeds Cancer”

Have you heard the saying, “sugar feeds cancer?” It is based on research performed nearly 100 years ago by Dr. Otto Warburg, who won the Nobel Prize. Dr. Warburg found that cancer uses sugar as an energy source. (1) As you probably know, PET scans use radiolabeled glucose because we know that cancerous tumors readily take up this contrast agent, allowing for visualization of cancer in the body.

When most people think of sugar, they think of the white granular substance used to sweeten foods. We all know about the dangers of sugar consumption, so eliminating sugar in this form is a no-brainer. However, other people associate sugar with any carbohydrate. This not only includes white sugar, but also other processed foods such as chips and pasta, as well as many fruits and vegetables as well. In recent years, strictly limiting carbohydrates in an attempt to treat cancer has become popular. When carbohydrates are restricted, to the point that almost no carbohydrates are consumed, the body makes ketones to use as an alternative energy source. Thus, this dietary approach is known as the ketogenic diet. With this approach, all carbohydrates are assumed to be equally bad, regardless of whether they come from a piece of cake, a bowl of rice, or a banana.

However, there are a few problems with the ketogenic diet. The ketogenic diet assumes that cancer can only feed on sugar, and that by eliminating virtually all carbohydrates from the diet, we will “starve” cancer. Although it sounds like a nice idea, this is simply not true. In fact, cancer uses multiple substances for fuel.

Did you know that cancer also uses amino acids, the building blocks of protein, for energy? Amino acids glutamine (2) and methionine (3) have been shown to be significant fuel sources for cancer cells. In addition, excess protein consumption can be converted into sugar by the body, a process known as gluconeogenesis. High protein diets, which are easy to fall into as a result of reducing carbohydrates substantially on a ketogenic diet, should be avoided.

In addition, cancer cells can utilize fats for fuel. This is important to know, since the ketogenic diet is a very high fat diet – as high as 85-90% of total calories consumed. Research has shown that fatty acids, which are the components of lipids, can be used by cancer cells for fuel. (4)

When carbohydrates are limited in the diet, the body makes ketones to compensate for the lack of carbohydrates. Ketones can be used by the body’s cells for energy, and for a long time, it was assumed that ketones could not be used by cancer cells. However, recent research has uncovered just the opposite: cancer cells can use ketones for energy. (5) One hypothesis is that the higher risk of cancer in diabetics is not simply due to increased blood sugar, but also to the higher amount of ketones present in the blood.

In addition to carbohydrates, amino acids, fatty acids, and ketones, cancer can (and does) use naturally occurring substances in the body for fuel. These include:

  • Iron
  • Copper
  • Vitamin B12
  • Estrogen
  • Progesterone
  • Testosterone

As you can see, cancer does not simply rely on sugar for energy! When one energy source is removed, cancer will simply use more of the other available energy sources. Cancer is highly adaptable! We are likely to discover even more potential fuel sources for cancer cells in the future.

Given this information, what does a proper anti-cancer diet look like? After all, we can’t limit all potential fuel sources for cancer. However, we can approach nutrition in an intelligent, science-based fashion.

The key is to limit methionine, since healthy cells do not require methionine but cancer cells do. (6) Research suggests that a plant-based diet consisting largely of organic fruits, vegetables, and some legumes is best. Although these are not low carbohydrate foods, they contain a significant amount of fiber, and this renders the carbohydrates less usable by cancer cells. High fiber diets, with fiber coming from whole foods rather than a fiber supplement, has been shown to play a pivotal role in reducing risk of multiple types of cancer. (7)

A moderate amount of grains, such as buckwheat, quinoa, and sprouted grains, is permissible. Animal protein and dairy should be limited, but not completely excluded. Of course, eliminating processed foods, and their unfavorable constituents including sugar, high fructose corn syrup, artificial sweeteners, artificial colors, trans fats, and all other fake man-made ingredients, is essential.

In addition, I have found value in fasting, which involves the strategic and purposeful avoidance of food for specific periods of time. Fasting has been shown to reduce inflammation, support the immune system, improve cognitive function, and enhance longevity. (8) The longevity benefit from fasting is due to its ability to mimic caloric restriction, which is the only conclusive method of extending lifespan. Interestingly, methionine restriction also mimics caloric restriction in the body, so it can also be thought of as a life extension strategy. A powerful one-two punch for sure!

This dietary strategy provides wholesome food which can be used by the body for health and optimal functioning, while also targeting cancer’s Achilles heel. It also provides support for individuals undergoing cancer treatment, providing an environment for treatments to work better. Perhaps most importantly, it is a very doable diet which can be adhered to over the long term, which cannot be said for many fad anti-cancer diets. After all, what we ultimately want is a lifestyle.

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  1. Warburg, Otto H. “On The Origin of Cancer Cells.” Science3191 (1956): 309-14.
  2. Wise DR and Thompson CB. Glutamine addiction: a new therapeutic target in cancer. Trends Biochem Sci 2010; 35(8): 427-33.
  3. Cellarier E, Durando X, Vasson MP, et al. Methionine dependency and cancer treatment. Cancer Treat Rev 2003; 29(6): 489-99.
  4. Corbet C and Feron O. Emerging roles of lipid metabolism in cancer progression. Curr Opin Clin Nutr Metab Care 2017; 20(4): 254-60.
  5. Bonuccelli G, Tsirigos A, Whitaker-Menezes D, et al. Ketones and lactate “fuel” tumor growth and metastasis. Cell Cycle 2010; 9(17): 3506-14.
  6. Cavuoto P and Fenech MF. A review of methionine dependency and the role of methionine restriction in cancer growth control and life-span extension. Cancer Treat Rev. 2012; 38(6):726-36.
  7. Shankar S and Lanza E. Dietary fiber and cancer prevention. Hematol Oncol Clin North Am 1991; 5(1): 25-41.
  8. Brandhorst S, Choi IY, Wei M, et al. A periodic diet that mimics fasting promotes multi-system regeneration, enhanced cognitive performance, and healthspan. Cell Metab 2015; 22(1): 86-99.