Fast Take: Does Eating Sugar Cause Cancer?

Identifying new mechanisms and pathways are key in science. They help answer long-term questions and also generate new scientific questions. And figuring out even one step of a pathway takes a significant amount of time. For example, I spent five years in graduate school teasing apart a very small pathway in human epithelial cells. Five years!

Findings from a recent study, published in Nature Communications, examined the glucose metabolism pathway in yeast and cancer cell lines, leading to some interesting new findings. And since the press release led with “scientists reveal the relationship between sugar and cancer”, it’s not surprising that this new study is receiving frenzied attention. Now before you swear off sugar for the rest of your life, let’s first pause and take a closer look at the study’s methods and findings. Then we’ll see how these results fit into what we know about sugar, diet and cancer connection.

Before we get to the paper, let’s first discuss what sugars are and what they do. Sugars are digestible carbohydrates made up of molecules called saccharides, which can be found naturally in some foods and beverages or added as ingredients in others. Monosaccharides are made up of a single sugar molecule, such as glucose or fructose. Monosaccharides can link together in pairs to form disaccharides like sucrose, commonly known as table sugar. Oligosaccharides are when a few saccharides link up and polysaccharides are chains of ten or more saccharides. Sugars serve as the body’s main source of energy, meaning that all cells (both cancerous cells and non-cancerous) use glucose for energy.

Why did the study examine the link between sugar and cancer?

It has long been known that cancerous cells use higher amounts of sugar compared to non-cancerous cells, which is known as the Warburg effect. However, it has been a lingering question in the field if this effect is merely a symptom of cancer or if it is what causes cells to become cancerous. In addition, it is not fully understood how sugar is broken down in cancerous cells. This study aimed to answer some of these questions.

What did the study examine?

The study examined how glucose is processed for energy in yeast and cancer cells, using model organisms and cell lines. Yeast was used as a model organism since yeast uses glucose similarly to cancerous cells. The study found that both yeast and cancer cells broke down glucose using the same pathway and led to the multiplication of both yeast and cancer cells. What was particularly groundbreaking is that they found this pathway was conserved in both yeast cells and human cancer cells.

Did the study find a link between sugar and cancer?

Hearing it straight from the horse's mouth is the best way to have a question answered. Co-author Johan Thevelein stressed how these findings need to be appropriately put into context saying, “Some people are interpreting that we have found a mechanism for how sugar causes cancer, but that is certainly not the case.”

In addition, while the press release led with an over-stated headline, later the document emphasized that the sugar-cancer link had not been established, stating, “The next step is to find out whether these results also apply to patients. To do this, clinical trials with oncologists have to be developed. Only after results from these kind of trials are known, statements can be made about possible consequences for cancer treatments and adjusted diets.”

These are important takeaways since the study was conducted in model organisms and cell lines. While these types of experimental designs are key to teasing apart mechanisms and pathways, these findings cannot be directly applied to how cancerous cells act in the human body. Dr. Juan Manuel Schvartzman, a medical oncology fellow at Memorial Sloan Kettering Cancer Center, emphasizes this point: “We now know that in vivo, cancer cells that make up a tumor are not all the same. Some may take up a lot of sugar and some may not and still grow."

Should this new research affect my diet?

There are many risk factors for developing cancer, including diet and obesity. While the amount of sugar you eat can play a role in your health, sugar by itself is not a risk factor for cancer. According to the National Cancer Institute, "no studies have shown that eating sugar will make your cancer worse or that, if you stop eating sugar, your cancer will shrink or disappear".

But that’s not to say that sugar shouldn’t be limited in the diet; it should be. The 2015-2020 Dietary Guidelines for Americans recommend limiting intake of added sugars to less than 10 percent of total calories per day. Limiting added sugars doesn’t mean eliminating all sugars from your diet. Sugars (natural and added) can be part of a healthy eating pattern. Sugars are added to many nutrient-dense foods. More importantly, they’re also found naturally in many of the healthiest foods like fruits, vegetables and dairy products. Avoiding these foods would mean missing out on a ton of nutrients like fiber, vitamins and minerals. If you’re looking to reduce the amount of added sugars in your diet, here are a few tips.

  • Primarily drink water, non- or low-fat milk, and 100% juice. Other options include unsweetened coffee or tea, nutrient-dense beverages and drinks sweetened with low- or no-calorie sweeteners.
  • Focus on whole fruits. Choose a wide variety of colors of fruits. When choosing canned, dried or frozen options, select those that are unsweetened or packed in their own juice or water.
  • Make half your grains whole grains. Look for whole grain information declared on the front of pack and in the ingredients list. Use the Nutrition Facts label to choose varieties that contain higher fiber or lower added sugars.

So don’t let scary headlines or social media posts scare you into avoiding sugar at all costs. Instead focus on a healthy eating pattern that works for your lifestyle, fits your taste preferences and hits your budget needs. 

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