• Sugar is the main source of energy in every cell
  • Cancer cells demand more energy than normal cells
  • The amount of sugar intake is indirectly linked to cancer risk

All cells in our body, normal or cancerous, need sugar to sustain growth, metabolism, and replication (1). In order to manage these wide range of functions, cells rely on energy stored within the chemical bonds that hold complex organic food molecules (such as sugar molecules) together (1). Cells make energy-rich molecules like  Adenosine triphosphate (ATP) and Nicotinamide adenine dinucleotide (NADH) via energy pathways that occur in mitochondria,  “the powerhouse of the cell”. Any excess energy is stored in larger, energy-rich molecules such as starch, glycogen and lipids (1).

Cancer cells grow much more rapidly than normal cells, hence, taking up more glucose compared with normal surrounding tissue. Energy pathways found in cancer cells lead to creation of potent activator molecules (e.g. RAS protein) that help to regulate cell growth and differentiation, known as The Warburg effect (2).

Does sugar “feed” cancer?

So far, studies show no evidence of a correlation between the level of sugar intake and cancer cancerous’ cell survival (3). Moreover, misconceptions about cancer causes, and the inevitable anxiety of trying to completely avoid “all sugar”, can lead to unnecessary worry and stress (4). This increases the level of hormones that can raise blood sugar levels and suppress our immune system that fights diseases (5). Also, because some treatments can result in weight loss in cancer patients, poor nutrition from restrictive diets by eliminating foods that are good sources of fiber and vitamins, could be life-threatening to them (4).

Fig.1. Choose your food wisely. Image adapted from (6).

However, there is an indirect link between sugar and cancer…

Studies have shown that any excess energy from glucose breakdown is stored as fat in our body. According to Clare McKindley, a clinical dietitian in MD Anderson’s Cancer Center, too much daily sugar can cause weight gain (7).  This, together with lack of exercise can increase cancer risk (7). Being overweight or obese increases the risk of 13 different types of cancer, making it the second most common preventable cause of cancer (after smoking) (8). Overweight is considered a BMI (the weight in kilograms divided by the square of the height in meters) of 25.0 to 29.9 and obesity a BMI of 30 or more, in adults (9). According to a research published in The New England Journal of Medicine, in 2016, more people are overweight or obese than are underweight (9). Furthermore, 640 million adults in 2014 and 110 million children and adolescents in 2013 were obese(9).  In 2013, an estimated 4.5 million deaths worldwide were caused by overweight and obesity(9).  9% of cancer burden among women in North America, Europe, and the Middle East are obesity-related (10).

Fig.2. Definitions of Classes of Overweight and Obesity. Image adapted from (9)

Fig.3. Strength of the Evidence for a Cancer-Preventive Effect of the Absence of Excess Body Fatness, According to Cancer Site or Type. Image adapted from (9)

How much sugar should we eat?

According to the American Heart Association, for women the optimal amount is no more than six teaspoons of sugar per day (25 grams), and for men no more than nine teaspoons of sugar per day (36 grams) (11). This equals to about 100 calories for women and 150 for men(11).  Most Americans eat more than about 22 teaspoons per day (12). That’s nearly four times more calories than recommended with absolutely no nutritional or cancer-fighting benefit (13).


The sugar that is found in fruits together with the numerous vitamins, minerals, antioxidants, phytochemicals, and fiber they contain must be part of our diet for a healthy and cancer-free life. By any means, eating healthy is not about excluding food rather than choosing it wisely.

COPYRIGHT: This article is the property of We Speak Science, a non-profit institution co-founded by Dr. Detina Zalli and Dr. Argita Zalli. The article is written by Rina Mehmeti and Driton Bajrami, University of Prishtina, Kosovo.


1. https://www.nature.com/scitable/topicpage/cell-energy-and-cell-functions-14024533

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783224/

3. https://www.rogelcancercenter.org/living-with-cancer/mind-body-side-effects/nutrition/sugar-and-cancer-does-sugar-increase-cancer-risk

4. https://scienceblog.cancerresearchuk.org/2017/05/15/sugar-and-cancer-what-you-need-to-know/

5. https://www.mayoclinic.org/diseases-conditions/cancer/in-depth/cancer-causes/art-20044714

6. https://www.aicr.org/reduce-your-cancer-risk/diet/sugar-and-cancer-risk.html

7. https://www.mdanderson.org/publications/focused-on-health/FOH-cancer-love-sugar.h14-1589835.html

8. https://scienceblog.cancerresearchuk.org/2016/10/11/the-second-biggest-preventable-cause-of-cancer-being-overweight/

9. https://www.nejm.org/doi/full/10.1056/NEJMsr1606602


11. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/sugar/added-sugars

12. https://www.hopkinsmedicine.org/health/wellness-and-prevention/finding-the-hidden-sugar-in-the-foods-you-eat

13. https://medicalxpress.com/news/2019-03-evidence-strong-sugar-cancer.html