What Is the Main Idea?

Does drinking sugary drinks lead to cancer of the digestive system? Studies have been completed to find an answer to this question, but, so far, the results have not been clear. The authors of the research article “Consumption of Sugar-Sweetened Soft Drinks and Risk of Gastrointestinal Cancer: A Systematic Review and Meta-Analysis of Observational Studies”, published in the journal Oncology, aimed to gather together all of the information from previous studies, and see whether the combined information could give clearer answers.

What Else Can You Learn?

You can learn about different types of digestive system cancer and also about how drinking sugary drinks can affect the body.

What Is Gastrointestinal Cancer?

Gastrointestinal cancer, or GI cancer for short, refers to cancer in the eating and digestive organs of the body. This includes the esophagus (our gullet, or food tube from mouth to stomach), the stomach, the liver and pancreas (both organs which produce digestive “juice”), and the intestines (including our bowel).

How Common Is Gastrointestinal Cancer?

GI cancer happens often, and people can often die from it. The authors report that, in 2020, across the world, 1 in 4 people becoming ill with cancer had GI cancer, and 1 in 3 people who died from cancer had GI cancer. In different parts of the world, these number facts vary. For example, in Asia it is higher: 1 in 3 people becoming ill with cancer had GI cancer and 1 in 2 people who died from cancer had GI cancer. But in Northern America this is lower: 1 in 10 people becoming ill with cancer had GI cancer, and 1 in 4 people who died from cancer had GI cancer. Number facts for the regions of Latin America and the Caribbean, Africa, Oceania, and Europe fit between Asia and Northern America.

What Are Sugar-Sweetened Soft Drinks?

Sugar-sweetened soft drinks (referred to as SSSDs) are drinks that are sweetened with sugar. This sugar can be high-fructose corn sweetener (HFCS), honey, household sugar (sucrose), and others. HFCS is a manufactured sugar that has been used since the 1970s.

Why Are Sugar-Sweetened Soft Drinks a Health Problem?

The authors describe some research showing that regularly consuming HFCS resulted in problems with weight and other body processes. This connects with cancer, because unhealthy body processes such as inflammation and keeping a good balance of hormone production (such as insulin) can be the start of a cell-changing process (pathway) towards cancer.

Why Does Combining Information from Many Studies Give Better Answers?

The studies the authors found used simple research techniques and/or had few study subjects. By combining all the information from all the studies, the authors were able to look at the “big picture” and use complex and better research and statistical techniques to make a more confident conclusion.

Since studies on animals and on laboratory samples show it is likely that SSSDs can increase cancer risk, the authors predicted (hypothesized) that they would see a link after combining all the human studies together.

How Did the Authors Combine and Examine the Information from Previous Studies?

The authors carried out what is called a systematic review and meta-analysis. They searched research databases for all research on the use of SSSDs and risk of GI cancer. There are international guidelines for how to do this in the best way: such as using special databases, using particular search words, and following logical processes to carefully review and categorize what is found. Much of the article is devoted to explaining the processes and statistical calculations in detail. The authors ended up with information from 27 studies.

What Did the Authors Find out?

The authors had a main result and some sub-results. The main result was about the link between consumption of SSSDs and risk of GI cancer. The sub-results looked at information broken down into subsections such as region, gender, and type of study.

  • For the main result, the authors found that, yes, there is a definite link between drinking SSSDs and increased risk of developing GI cancer.
  • For the sub-results, this main result was clearest in studies with an approach of analyzing people who consumed SSSDs (cohort studies), rather than studies that analyzed people who already had GI cancer (case control studies).

The authors also found that the risk is particularly connected to developing colorectal cancer (cancer of the bowel). However, they didn’t find any connection between gender (male/female).

Another interesting statistical test that the authors did, was to consider SSSDs as a medicine, and see how the body reacts, called a dose–response analysis. Usually, this kind of statistical test is done to see if a medicine is effective and/or safe. In this situation, the authors were looking for safety issues for SSSDs. The test results also showed the authors that SSSDs do have a safety issue in terms of the risk of developing GI cancer.

How Can Sugar-Sweetened Soft Drinks Affect the Body?

The authors explained some possible reasons for why consuming SSSDs may increase the risk of GI cancer:

  1. High consumption of SSSDs can lead to becoming overweight, and being overweight is a well-known risk factor for developing GI cancer.
  2. Consumption of SSSDs can lead to an increase in fat around the body’s organs (which is different to fat that lies under the skin). Known as visceral adiposity, studies show that this can affect the way the body’s cells work and lead to the development of cancer.
  3. SSSDs have a high glycemic index. This means that, after consumption, the sugar levels in the blood rise and fall rapidly, which can trigger unhealthy changes in the body’s cell processes, leading to the development of cancer.
  4. SSSDs also contain chemicals for coloring and flavoring. Some of these chemicals have been classified by the International Agency for Research on Cancer as possibly cancer-causing

Take-Home Message

Consumption of sugar-sweetened soft drinks is connected to an increased risk of developing GI cancer. Although the authors used detailed statistical techniques to make this conclusion, they describe some weaknesses of their study and suggest that future research could look deeper into the sub-result themes and connections.

Although the authors do not specifically say how much sugar-sweetened soft drinks we can drink, it is common advice from nutritionists and dieticians that we should aim to avoid sugary and fatty diets. Each person should also speak with their health professional for individualized diet advice.

Note: This post is based on an article that is not open-access; i.e., only the abstract is freely available.

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