Sugar is sweet, but has a deadly history as a driver of the slave trade and diabetes.
Americans averaged only two pounds annually in 1820. That average rose to 123 pounds by 1970, and now stands at about 152 pounds annually.
About 57 of those staggering 152 annual pounds are as added sugars — see "How much added sugar do we eat, and how much should we?", near the end of this article.
Fruits, sweet potatoes, and other whole foods naturally high in sugars are not tied to health problems, although diabetics may need to limit their intake.
Copious consumption of added sugars — mostly from processed foods, desserts, and drinks (soda and fruit juice) — fuels the global rise in obesity, diabetes, and heart disease.
Growing evidence also suggests that sugary diets raise cancer risks, but research into this possible sugar-cancer link has been rather limited.
Clinical trials would need to be long, large, and expensive — and they'd be unethical, given the adverse effects of consuming lots of sugar.
So, research will likely be limited to epidemiological (population) studies that look for links between participants’ self-reported consumption of sugary drinks and new cancer diagnoses.
As it happens, the results of two large epidemiological studies — among the first to examine this question — were just published, and both suggest that sugary drinks raise cancer risks.
Before we get to the details of their authors' findings, let’s take a quick look at the history of research into sugar and cancer.
Prior indications that added sugars can promote cancer
Our coverage of this topic began in 2006, when evidence linked sugar to a deadly cancer: see Sugary Diets Raise Risk of Pancreatic Cancer Sharply.
It continued in 2012, with two reports: One summarized an evidence review suggesting that foods and drinks with added fructose raise cancer risks — see Does Fructose Fuel Cancer? — and another, titled Sugar Lack Kills Cancer: New Study Shows How, concerned the potential for dietary sugar to promote cancer growth.
A Swedish epidemiological (population) study published three years ago linked higher consumption of sugary drinks to higher risks for biliary tract and gallbladder cancer (Larsson SC et al. 2016).
And the results of a 2016 University of Texas rodent study suggest that, as our headline said, Sugar Fuels Breast Cancer — at least in mice.
Now, the evidence obtained from two recently published epidemiological studies seems likely to fuel fears about the consequences of downing lots of fruit juice and/or sugary sodas.
Epidemiological studies cannot prove a cause-effect relationship between diet or lifestyle and risk for developing cancer. However, both involved large numbers of participants, and their results were adjusted to account for the known effects of major cancer risk factors.
Study #1: French research links sugary drinks to greater cancer risk
A team of researchers based in France set out to look for any links between the risk for cancer and consumption of sugary drinks (fruit juice and/or sugary soda) or artificially sweetened “diet” beverages.
They looked for links between sweet drinks and the overall risk of cancer, as well as the risk of breast, prostate, and colorectal cancers (Chazelas E et al. 2019).
The French team analyzed data provided by participants in the NutriNet-Santé study, which involved 101,257 healthy French adults (21% men; 79% women) whose average age at its outset in 2009 was 42 years.
Each participant answered at least two 24-hour online diet surveys designed to measure their usual intake of 3,300 different foods and beverages, and their health outcomes were followed for up to nine years (2009-2018).
The diet surveys asked about the participants' usual consumption of sugar-sweetened beverages, fruit juices, artificially sweetened drinks — and any cancer diagnoses reported by participants were verified by checking their medical records and as well as health insurance databases.
The French researchers calculated statistical links between consumption of sweet drinks and cancer risk and adjusted the results to account for the effects of key cancer risk factors, including age, sex, educational level, family history of cancer, smoking status, and physical activity levels.
Alarmingly, the team’s analysis linked a 100 mL [3.5-ounce] per day rise in consumption of sugary drinks to an 18% higher overall cancer risk and a 22% risse in the risk of breast cancer.
And the analysis linked fruit juices and sugar-added sodas alike to comparably higher cancer risk, probably because they typically contain similar amounts of sugar.
The French team found no significant links between sugary drinks and the risk for prostate and colorectal cancers, but the number of prostate cancers in the reviewed studies was small, making it more difficult to detect meaningful associations.
Artificially sweetened (diet) beverages were not linked to higher risks for cancer, but the authors noted that consumption levels among the participants were relatively low, making it more difficult to detect meaningful associations.
The study's authors proposed several possible explanations for their results: the effects of sugar on visceral fat around vital organs, higher blood sugar levels, and higher levels of inflammation, all of which can raise cancer risk.
They also suggested the possibility that synthetic additives in some sodas might also play a role, although no prior studies have found such associations.
The French team’s conclusions included some astute advice: “These data support the relevance of existing nutritional recommendations to limit sugary drink consumption, including 100% fruit juice, as well as policy actions, such as taxation and marketing restrictions targeting sugary drinks, which might potentially contribute to the reduction of cancer incidence.”
Interestingly, men in the study reported a higher average daily consumption of sugary drinks (90.3 mL / 3 ounces) than the women (74.6 mL / 2.5 ounces).
Study #2: International investigation links sugary drinks to risk for early death
Earlier this year, scientists from Harvard University, China, and Canada published their analysis of data from two very large epidemiological studies: The Nurses’ Health Study (80,647 women) and the Health Professionals Follow-up Study (37,716 men).
Every two years, the participants in these famous studies — which lasted 34 and 28 years, respectively — answered surveys about their lifestyles, diets, and health status.
The international team concluded that drinking more sugar-sweetened drinks (e.g., soda or juice) raised the risk of early death from any cause — a finding they adjusted to account for the likely impacts of lifestyle factors known to affect cancer and cardiovascular risks.
Importantly, the reliability of the team’s conclusion was bolstered by their finding that the risk for early death rose in in a “dose-dependent” fashion, along with rising consumption of sugary drinks.
Compared with drinking sugary drinks less than once per month, the risk of early death rose with drinking more sugary beverages (soda or fruit juice):
And the team’s analysis found a higher risk of early death among women, compared with men who drank equal amounts of sugary beverages.
The link between sugary drinks and higher risk of early death was particularly strong for deaths from cardiovascular (heart-artery) disease.
Compared with people who drank sugary beverages infrequently, those who drank two or more daily were 31% more likely to suffer early death from CVD — with each additional daily sugary drink raising the risk of heart-related death linked by 10%.
The analysis also detected a more modest link between sugary drinks and the risk of early death from cancer, which was about equal for men and women.
A comment by study lead author Vasanti Malik echoed the French team’s advice: “Our results provide further support to limit intake of SSBs [sugar-sweetened beverages] and to replace them with other beverages, preferably water, to improve overall health and longevity.”
How much added sugar do we eat, and what's the limit?
The average American consumes about 57 pounds of added sugars annually.
That's two to three times the maximum annual intake — depending on gender — advised by the American Heart Association (AHA) and the World Health Organization (WHO).
The AHA and the WHO agree that adults shouldn’t consume more than 5% of daily calories from added sugars or natural sugars in honey or fruit juice.
That translates into a maximum of six teaspoons (25 grams or just under 1 ounce) of added sugar per day for women and nine teaspoons (38 grams or about 1½ ounces) for men.