Sugar keeps making headlines because of accumulating research on its known and potential risks, as well as new calls from government agencies and health organizations for us to cut down on it. Is sugar even worse than saturated or trans fat or sodium, as some nutrition experts and news reports claim? That’s difficult to say, but sugar is definitely a major concern, primarily because we’re consuming so much more of it than we used to. In the past, worries were confined to its increasing the risk of diabetes and obesity and its causing cavities, but now research has also linked sugar to heart disease, hypertension, strokes, gout, periodontal disease, fatty liver disease, and a host of other health problems.
“We are in the midst of a paradigm shift in research on the health effects of sugar, one fueled by extremely high rates of added sugar overconsumption,” as Laura Schmidt, Ph.D., professor of Health Policy at UC San Francisco, put it in a commentary in JAMA Internal Medicine. “Too much sugar does not just make us fat; it can also make us sick.”
These concerns pertain to the huge amounts of added sugar we’re consuming, not the sugar naturally found in foods such as fruit and dairy products. That added sugar is overwhelmingly sucrose (white table sugar) or high-fructose corn syrup, which are liberally added to as much as three-quarters of all packaged foods and beverages in the U.S.— not only “sweets” like candies and cookies, but also staples like breakfast cereal, pasta sauce, ketchup, baked beans, sweetened yogurt, bread, and soups. Added sugars also include honey, molasses, coconut palm sugar, agave, evaporated cane juice, and fruit juice concentrate, which sound healthier but are basically just sugar.
It’s theorized that large intakes of added sugar have adverse effects in the body via multiple pathways —notably by increasing inflammation, oxidative stress, and triglycerides (fats in the blood), impairing insulin regulation, and raising blood pressure.
Risks of added sugar
Here's a sprinkling of recent research:
Cardiovascular disease. In an important study in JAMA Internal Medicine, researchers analyzed national data from the past 20 years and found that the 10 percent of people who consumed the most added sugar (25 percent or more of daily calories) were almost three times more likely to die from cardiovascular disease than those consuming the least (less than 10 percent of daily calories), while those with intermediate sugar consumption had a one-third higher risk, on average. Elevated risk was seen regardless of body weight, physical activity level, age, sex, race/ethnicity, overall diet quality, and many other factors.
Stroke. In a large Swedish study in the Journal of Nutrition, which followed 68,000 healthy people (ages 45 to 83) for a decade, those drinking at least two cups of sugary beverages a day were about 20 percent more likely to suffer a stroke than those who rarely drank them.
Hypertension. In an analysis of data from 12 clinical trials, published in the American Journal of Clinical Nutrition, New Zealand researchers found that relatively high sugar intakes increased blood pressure by 6 to 8 points, on average. In fact, added sugar probably contributes more to hypertension than sodium does, concluded a review paper in the journal Open Heart.
How Much Sugar Is Too Much?
The new proposed Dietary Guidelines for Americans recommend a limit on sugar for the first time: no more than 10 percent of a person’s daily calories should come from added sugar.
Blood cholesterol and triglycerides. In a clinical trial in the American Journal of Clinical Nutrition, researchers from UC Davis found that sugary beverages (containing high-fructose corn syrup) significantly raised LDL (“bad”) cholesterol, triglycerides, and related risk factors in the blood of young adults in just two weeks. The participants were divided into four groups so that the beverages supplied various proportions of their daily calories — low (10 percent), medium (17.5 percent), or high (25 percent), compared to a control group that drank artificially sweetened soft drinks. The more sugar they consumed from the beverages, the worse the effects on their risk factors. The high-sugar group had particularly dramatic increases—their LDL rose by 16 points and triglycerides by 37 points. The previously mentioned New Zealand analysis pooled data from 37 other trials and also concluded that high sugar intake raises LDL cholesterol and triglycerides, independent of its effect on body weight.
Diabetes. A review in Mayo Clinic Proceedings confirmed that added sugar, especially fructose, is a “principal driver” of the epidemic of type 2 diabetes, as a result of its contribution to metabolic problems and ultimately insulin resistance. Table sugar (sucrose) is half fructose (and half glucose), while high-fructose corn syrup is usually 55 to 65 percent fructose. The authors noted that whole foods containing fructose, such as fruits, pose no problem for health and are linked to reduced diabetes risk. In a large population study in the European journal Diabetologia in 2015, researchers estimated that for every serving of sugary beverages consumed daily, the risk of developing type 2 diabetes increases by 22 percent, after controlling for factors such as body weight and total calorie intake.
Obesity-related deaths. Sugary beverages are associated with more than 180,000 obesity-related deaths worldwide each year, according to a studyrecently in Circulation. About 25,000 of those deaths occur in the U.S. Three-quarters of them are caused by diabetes, the rest by cardiovascular disease and some cancers. The researchers used data from the 2010 Global Burden of Disease Study, which focused on the health and mortality rates of more than 100 countries, and adjusted them for other factors that affect weight.
Shortened telomeres. In a study in the American Journal of Public Health, researchers from UC Berkeley, UC San Francisco, and other institutions analyzed data from national surveys and found that sugary beverages were associated with shortened telomere length. Telomeres are caps on the ends of DNA strands (chromosomes) that help protect them from damage as cells repeatedly divide. Having a high percentage of short telomeres has been linked to cancer, cardiovascular disease, and certain other age-related disorders. For more on telomeres, see Aging: What Telomeres Can Tell.
Rheumatoid arthritis. In an analysis of data from the long-running Nurses Health Study (I and II) in the American Journal of Clinical Nutrition in 2014, researchers found that drinking at least one sugary soda a day was linked with to an increased risk of rheumatoid arthritis, independent of weight and other dietary and lifestyle factors. It’s theorized that added sugar may increase the risk by promoting insulin resistance and/or inflammatory processes.
Early menarche (first menses). In a study in Human Reproduction, Harvard researchers found that among girls ages 9 to 14, those who drank sugary soft drinks often (at least 18 ounces a day) had their first period nearly three months earlier than girls who rarely consumed the drinks. Fruit juice was not associated with early menarche. The Harvard researchers controlled for body weight, calorie intake, exercise level, and other factors that could play a role. Early menarche is a health concern in part because it is associated with an increased risk of breast and endometrial cancer later in life.
Avoiding Added Sugar
Excessive sugar intake is usually a marker for a diet heavy in processed foods and high in calories, saturated fat, and sodium. But research now indicates that it boosts risk independently of overall diet.