There’s a national campaign to reduce sugar consumption. No wonder! Sugar contains calories but is completely devoid of nutrients. Although sugar supplies energy, it doesn’t help our body meet its requirements for vitamins and minerals. Plus, foods that are high in sugar cause a rapid spike in blood glucose and a surge in insulin release that contributes to insulin resistance and obesity.
By contributing to weight gain, a high-sugar diet is also linked with obesity. Yet eating a diet high in sugar has other downsides. Some studies link refined carbohydrates and sugar with a greater risk of heart disease, another common health problem. But there’s another common health condition that strikes fear in the hearts of many – cancer. Does eating a diet high in sugar also increase the risk of cancer?
Are High-Sugar Diets Linked with Cancer?
A recent review published in the Annual Review of Nutrition explored the issue of diets high in sugar and cancer risk by reviewing 37 prospective cohort studies. Prospective cohort studies are where researchers follow individuals that have similar traits and habits but differ in a particular variable of interest. In this case, the variable is sugar intake. By following people who are similar in most characteristics but differ in the amount of sugar they eat, you can see whether there is a risk of a particular health outcome, in this case, cancer is higher. However, a correlation doesn’t necessarily show that sugar CAUSES cancer. There could be some other factor that sugar eaters have in common that the study couldn’t control for. These studies do provide valuable information though.
Based on analysis of these studies, 4 out of 15 showed a link between higher total intake of sugar and a greater risk of cancer. Remember, sugar comes in a variety of forms. There’s added sugar, like that in packaged foods and sugar you add to foods from the sugar bowl. There’s also natural sugar that you get when you bite into a piece of fruit. The sugar in a piece of fruit comes in a total package that also includes fiber and phytochemicals. These components slow the rise in blood sugar you get when you eat sugar via a less healthy vehicle, like a cookie or brownie.
When the researchers looked at added sugar, 2 out of 5 studies showed a higher risk of cancer with higher intakes of sugar. But the strongest association was with sugary beverages, like soft drinks and other sugar-sweetened beverages. Eight of the 15 studies found a significantly higher risk (23-200% increased risk) in those who consumed the most sugary beverages. What can we conclude? Consuming sugary beverages and foods with added sugar is more strongly linked with cancer risk than getting sugar naturally through whole foods, such as a piece of fruit.
How Might Cancer and Foods High in Sugar Be Linked?
Although there may be a link, how might sugar increase the risk of cancer? For one, eating a diet high in sugar is linked with obesity. That’s important since research correlates obesity with a greater risk of at least 13 forms of cancer. Obesity is also a pro-inflammatory state. Fat cells produce inflammatory chemicals called cytokines that fuel low-grade inflammation.
Studies show that inflammation stimulates a variety of pathways linked with the initiation and survival of cancer. Plus, chronic inflammation can lead to mutations in a DNA, a cell’s genetic material. If a mutation alters genes that suppress tumor formation, that increases the risk of a cancer forming and surviving. In addition, some research suggests that sugar increases oxidative stress. When free radicals form from oxidative stress, they damage a cell’s DNA and other important structures that keep the cell from going “rogue” and replicating out of control as cancer does.
Finally, sugar may encourage the growth of tumor cells by its impact on insulin. When you eat a sugary food, it causes a rapid, more sustained rise in insulin. Insulin is a growth-promoting hormone that increases the rate at which cells divide, including cancer cells. Most of us form cancerous cells all the time but most don’t survive long enough to cause problems. But, when you supply the right environment and give tumors the right growth factors, like insulin, to promote growth they have a better chance of flourishing and gaining a foothold in your body. Higher insulin levels and type 2 diabetes itself is linked with a greater risk of some types of cancer, including breast, prostate, colon, uterine, and pancreatic cancer.
Not Just Sugar, Avoid Highly Processed Foods Too
Highly processed foods typically contain added sugar and refined carbohydrates. Plus, ultra-processed foods have a number of potential components that may be associated with cancer risk. For one, manufacturers use cheap oils to manufacture them, many of which are high in pro-inflammatory omega-6 oils. They also have a low fiber content. Fiber is important for preventing a rapid rise in blood sugar. The way foods are processed is problematic too. Some ultra-processed foods are heated to high temperatures. Exposure to high heat causes some foods to form carcinogenic chemicals such as acrylamides and heterocyclic amines. Even the packaging is problematic. Studies show that food packaging may contain endocrine disruptors, chemicals that disrupt hormones. Processed meat is also preserved with nitrates that are likely carcinogens.
In fact, a study published in the British Medical Journal showed a link between ultra-processed foods and cancer. It found that as little as a 10% dietary increase in highly processed foods was associated with a more than 10% increase the risk of cancer. These foods are also low in micronutrients and a micronutrient-rich diet is important for cancer prevention and for overall health. Stick to whole foods!
The Bottom Line
Some studies show a correlation between sugar consumption and a higher risk of cancer and there are mechanistic reasons why sugar may increase the risk. At the very least, sugar offers no nutrition, only empty calories. So, toss the sugary foods and ultra-processed junk. It’s a smart move for your health and, possibly, your risk of developing cancer.
Annual Review of Nutrition. Vol. 38:17-39 (Volume publication date August 2018)
Scientific Reports. Volume 8, Article number: 10805 (2018)
Journal of Nutrition and Metabolism. Volume 2012, Article ID 238056.
Am J Clin Nutr. 2012;96(2):345-55.
Life Extension Magazine. June 2016. “The Insulin/Cancer Connection”