In our quest to live healthy lives, our diet remains one of the most critical factors within our control. This may be why the sugar and cancer debate has garnered attention and intense discussions among health professionals and the public for decades. Sugar is not the first dietary component to be vilified. Initially, fat was labeled as the primary culprit behind the rising rates of heart disease and obesity, which led to the proliferation of low-fat foods and high-protein diets. Despite these dietary shifts, obesity rates continued to rise steadily, suggesting that simply cutting out fat was not the solution (1).
In recent years, the focus has shifted from fat to sugar, particularly concerning its potential link to cancer. Sugar, often referred to as glucose or carbohydrates (see inset text box on “Sugar Classification”), is an essential energy source for our bodies. The question of whether sugar causes cancer or fuels its growth does not have a simple yes or no answer. Instead, it involves understanding the complex interactions between sugar consumption, metabolic processes, and overall health.
Figure 1. Classification of sugars (carbohydrates) and some important mono- and disaccharides in human nutrition, available in nature.
Cancer Metabolism
The sugar vs. cancer debate was first sparked in the 1920s when a German physiologist named Dr. Otto Warburg observed that cancer cells consume glucose at a much higher rate than normal cells (2). Cancer cells use a type of metabolism called aerobic glycolysis that produces energy 10-100 times faster than the type of metabolism normal cells use (cellular respiration). However, aerobic glycolysis is far less efficient than cellular respiration. While normal cells get 36-38 molecules of ATP (energy) per molecule of glucose, cancer cells only get two molecules of ATP per molecule of glucose (3). To make up for this inefficiency, cancer cells have to consume significantly more glucose to get energy—about 200 times more than normal cells! (4)
In fact, this high glucose consumption is exactly the reason oncology utilizes PET scans. PET scans detect areas of high glucose uptake in the body by using a radioactive glucose analog. Since cancer cells consume more glucose than normal cells, they show up brightly on the scans, allowing doctors to locate tumors and assess their metabolic activity.
But if cancer cell metabolism is so much less efficient than normal cells, why do cancer cells get energy in this way? There are a few reasons why this inefficiency is advantageous:
- Faster Energy Production: Aerobic glycolysis produces energy at a much faster rate through a faster turnover of glucose, which supports the rapid growth and division of cancer cells (2).
- Zero Oxygen Requirement: Cancer cell metabolism doesn’t require oxygen, while normal cell metabolism does. Tumors often have regions with low oxygen levels (hypoxia), so this metabolic pathway allows cancer cells to survive even when there’s no oxygen (5).
- Byproducts Support Growth: Aerobic glycolysis creates byproducts such as lactate, pyruvate, and glutamate, which are useful for rapid growth. These byproducts also create an inflammatory and acidic tumor microenvironment (TME) that makes it easier for the tumor to avoid detection by the immune system (2).
Given this metabolic adaptability, one might wonder if reducing sugar intake could effectively starve cancer cells. Unfortunately, no—when sugar is scarce, both healthy cells and cancer cells can utilize other sources of energy, such as proteins and fats. This means that simply eliminating sugar from the diet is unlikely to starve cancer cells without also depriving normal cells of their necessary energy sources. Thus, targeting cancer metabolism requires a more nuanced approach than just cutting out sugar.
Does Sugar Cause Cancer?
We’ve established that cutting out sugar is not an effective way to “starve” cancer cells. However, a common question that follows is whether sugar causes cancer. The answer is not straightforward; while sugar itself doesn’t directly cause cancer, excessive consumption can lead to conditions that increase cancer risk.
Excessive sugar intake contributes to obesity, diabetes, and chronic inflammation, all of which are known to elevate the risk of developing cancer. The indirect but undeniable link between sugar and cancer stems from the fact that excess sugar consumption leads to an increase in calorie intake. This surplus in calories contributes to metabolic conditions such as obesity and insulin resistance, which can eventually develop into diabetes. These conditions create a cascade of harmful effects in the body that act as fuel to the fire of cancer development and progression.
In the context of pre-diabetes and diabetes, several factors can contribute to cancer growth. Firstly, increased insulin production can create an environment that supports cancer cell growth, multiplication, and survival (6). As the body’s cells progressively struggle to absorb sugar, more glucose remains in the bloodstream, providing an abundant energy source for cancer cells (4). Elevated levels of inflammatory hormones and growth hormones in individuals with pre-diabetes and diabetes can also contribute to the proliferation and spread of cancer cells (7). These combined factors create a favorable environment for cancer to thrive and progress.
Obesity is also a major contributor to cancer development and growth due to several interconnected physiological and metabolic disturbances. These include:
- Depressed Immune System: Excess body fat can impair the immune system’s ability to detect and fight off cancerous cells (8).
- Dysbiosis: An imbalance in gut microbiota can further weaken the immune system and contribute to systemic inflammation (9).
- Chronic Inflammation: Obesity leads to persistent, low-grade inflammation throughout the body, creating an environment conducive to cancer development (10).
- Pro-Inflammatory Hormones: Fat tissue, especially abdominal fat, releases a continuous stream of harmful, pro-inflammatory hormones that can promote cancer growth (10).
- NAFLD Contribution: Non-alcoholic fatty liver disease (NAFLD), commonly linked to obesity, increases the risk of liver cancer (11).
- Altered Hunger Hormones: Obesity disrupts hunger hormones, promoting overeating and further weight gain, which can drive cancer progression (12).
- Altered Sex Hormones: Obesity can alter sex hormone levels, contributing to the development and progression of cancers such as breast and endometrial cancer (13).
The intricate relationship between sugar and cancer highlights how excessive sugar intake indirectly contributes to cancer development and progression. While sugar itself does not directly cause cancer, it creates a fertile environment for cancer cells to thrive by fostering pro-cancer conditions.
Sugar Overload: How Overeating Sugar Affects Health
It is essential to recognize that sugar is not the sole cause of health issues. The overconsumption of anything, whether it’s sugar, alcohol, or even protein, can lead to health problems. Our bodies thrive on balance, and too much of any one thing can disrupt that balance and contribute to various diseases. This principle of balance is at the core of Hope4Cancer’s Garden Food Plan, which emphasizes a diet based on whole, natural foods reminiscent of those originally present in the Garden of Eden—a balanced array of fruits, vegetables, nuts, and seeds that provide optimal nutrition without excess (14).
However, the reality is that we are consuming far too much sugar. According to the American Heart Association (AHA), the average American consumes about 123 grams of sugar per day (15). This intake is almost five times the amount recommended for women, which is 25 grams, and more than three times the recommended amount for men, which is 36 grams (16).
Interestingly, this excessive sugar consumption is not primarily due to desserts and sweet treats. In fact, only about one-fifth of our sugar intake comes from desserts (16). The majority of the sugar we consume is hidden in ultra-processed foods such as soda, soups, bread, sauces, and yogurt. These sugars are often added during processing and can be easily overlooked because they come under various names—over 60 different names, to be precise.
There are two main types of sugars: intrinsic (naturally occurring) and extrinsic (non-naturally occurring) sugars. Intrinsic sugars are like those found in fruits and vegetables and are built into the food’s cellular structure. Extrinsic sugars, known by many other names, including free sugars, added sugars, and refined sugars, are added during processing, preparation, or consumption.
According to AHA guidelines, women should aim for less than 25 grams of free sugars per day, and men should aim for less than 36 grams. For our cancer patients, we recommend that they completely avoid free sugars. This does not include intrinsic sugars in fruits and vegetables, which are naturally present and contain essential vitamins, minerals, fiber, and antioxidants. These foods are more filling due to their fiber and water content, helping to control hunger and prevent overeating. It’s nearly impossible to overeat foods with intrinsic sugars; few of us would be able to eat six apples in one sitting, but all of us could easily consume a pack of cookies or a can of soda without thinking twice. Moreover, foods with intrinsic sugars have a more balanced metabolism due to the slower release of glucose into the bloodstream, which helps maintain stable energy levels (16).
From a naturopathic perspective, nutrients in plants (including intrinsic sugars) should not be viewed as separate entities but as part of the whole nutrient profile of the plant. Our good friend and famous naturopath, Dr. Robert Cass from Physica Energetics, calls this part of the “holographic energetic imprint” that carries the highest frequencies of the focal point of each entity that allows it to propagate life from seed to seed or graft to graft. That is also why, in our Garden Food Plan®, we talk about foods from the “Garden” that are safe to consume.
The Risks of Artificial Sugars and Sweeteners
Even though artificial sugars have zero calories, they can still pose significant health risks. These sweeteners, such as sucralose, aspartame, and erythritol, are chemical compounds concocted in a lab that lack the benefits of intrinsic sugars, making them an empty addition to your diet.
Even despite their zero-calorie claims, studies have shown that artificial sweeteners do not contribute to weight loss or help maintain a healthy weight. One extensive analysis, which examined over 400,000 people over the course of ten years, found that the routine consumption of non-nutritive sweeteners did not show clear benefits for weight management. These sweeteners have been associated with increased appetite and calorie consumption, counteracting their intended purpose! (17)
Artificial sweeteners have been linked to an increased risk of heart disease and strokes. Research has demonstrated that the consumption of sweeteners like sucralose, aspartame, erythritol, and, most recently, xylitol can elevate the risk of developing cardiovascular diseases through regular consumption (18). This makes them a poor substitute for intrinsic sugars, as their potential health risks outweigh the benefits of their zero-calorie content.
The only sweeteners that are considered acceptable are natural and plant-based alternatives such as allulose and monk fruit. These sweeteners offer a more health-conscious choice without the adverse effects associated with chemical-based artificial sugars. By opting for natural alternatives, you can enjoy sweetness without compromising your health. However, be vigilant when selecting these products, as some manufacturers blend natural sweeteners with sugar alcohols or other additives while marketing them solely under the name of the natural component. This practice is common because it can enhance taste and texture while keeping costs down, potentially misleading consumers about the true composition of the product. Also, be watchful of “diet” products that often contain these artificial sweeteners. We recommend you enjoy intrinsic sugars like honey and maple syrup (in moderation, of course!) rather than indulge that proverbial sweet tooth with lab-made artificial sweeteners!
Understanding the Bigger Picture
The sugar and cancer debate cannot be settled by a simple yes or no. While it is true that cancer cells consume glucose (the simplest form of sugar accessible to cells) faster than normal cells, eliminating sugar entirely from the diet is not a sufficient strategy to starve cancer cells. Both healthy cells and cancer cells can utilize proteins and fats for energy in the absence of sugar.
Nevertheless, excessive sugar intake is one of many factors contributing to chronic diseases such as obesity, diabetes, and inflammation. These conditions lead to immune and hormonal changes that have been directly linked to cancer. Therefore, it is crucial to pay attention to our sugar intake, especially given that we are consuming far too much as a society.
While general guidelines suggest limits of extrinsic sugar of 25 grams for women and 36 grams for men daily, the truth is that the lower its consumption, the better. For optimal health, especially for those dealing with cancer, the goal should be to minimize or completely eliminate extrinsic sugar intake. Pay close attention to processed foods and hidden sources of sugar on ingredient labels, and avoid artificial sweeteners due to their links with negative health effects. Ensure that your plate contains a balance of healthy nutrients: lean protein, grains with complex carbs, and plenty of fruits and vegetables with a variety of colors. By following these practical guidelines, you will be able to manage your sugar intake better and promote overall health, reducing the risk of chronic diseases and supporting cancer prevention and recovery efforts.
References
- Hall, K.D., Did the Food Environment Cause the Obesity Epidemic? Obesity (Silver Spring), 2018. 26(1): p. 11-13.
- Liberti, M.V. and J.W. Locasale, The Warburg Effect: How Does it Benefit Cancer Cells? Trends Biochem Sci, 2016. 41(3): p. 211-218.
- Vazquez, A., J. Liu, Y. Zhou, et al., Catabolic efficiency of aerobic glycolysis: the Warburg effect revisited. BMC Syst Biol, 2010. 4: p. 58.
- Chae, Y.C. and J.H. Kim, Cancer stem cell metabolism: target for cancer therapy. BMB Rep, 2018. 51(7): p. 319-326.
- Bartrons, R. and J. Caro, Hypoxia, glucose metabolism and the Warburg’s effect. J Bioenerg Biomembr, 2007. 39(3): p. 223-9.
- Zhang, A.M.Y., E.A. Wellberg, J.L. Kopp, et al., Hyperinsulinemia in Obesity, Inflammation, and Cancer. Diabetes Metab J, 2021. 45(4): p. 622.
- Oguntibeju, O.O., Type 2 diabetes mellitus, oxidative stress and inflammation: examining the links. Int J Physiol Pathophysiol Pharmacol, 2019. 11(3): p. 45-63.
- Bahr, I., J. Spielmann, D. Quandt, et al., Obesity-Associated Alterations of Natural Killer Cells and Immunosurveillance of Cancer. Front Immunol, 2020. 11: p. 245.
- Singh, S., P. Sharma, D.K. Sarma, et al., Implication of Obesity and Gut Microbiome Dysbiosis in the Etiology of Colorectal Cancer. Cancers (Basel), 2023. 15(6).
- Himbert, C., M. Delphan, D. Scherer, et al., Signals from the Adipose Microenvironment and the Obesity-Cancer Link-A Systematic Review. Cancer Prev Res (Phila), 2017. 10(9): p. 494-506.
- Global Burden of Disease Liver Cancer, C., T. Akinyemiju, S. Abera, et al., The Burden of Primary Liver Cancer and Underlying Etiologies From 1990 to 2015 at the Global, Regional, and National Level: Results From the Global Burden of Disease Study 2015. JAMA Oncol, 2017. 3(12): p. 1683-1691.
- Lin, T.C. and M. Hsiao, Leptin and Cancer: Updated Functional Roles in Carcinogenesis, Therapeutic Niches, and Developments. Int J Mol Sci, 2021. 22(6).
- Carlson, M.J., K.W. Thiel, S. Yang, et al., Catch it before it kills: progesterone, obesity, and the prevention of endometrial cancer. Discov Med, 2012. 14(76): p. 215-22.
- Jimenez, A., Hope For Cancer: 7 Principles to Remove Fear and Empower Your Healing Journey. 2019, Austin, TX: Envision Health Press.
- Zuker, C.S., Food for the brain. Cell, 2015. 161(1): p. 9-11.
- American Heart Association. How Much Sugar is Too Much? Website article, last reviewed May 23, 2024.
- Azad, M.B., A.M. Abou-Setta, B.F. Chauhan, et al., Nonnutritive sweeteners and cardiometabolic health: a systematic review and meta-analysis of randomized controlled trials and prospective cohort studies. CMAJ, 2017. 189(28): p. E929-E939.
- Debras, C., E. Chazelas, L. Sellem, et al., Artificial sweeteners and risk of cardiovascular diseases: results from the prospective NutriNet-Sante cohort. BMJ, 2022. 378: p. e071204.
