Americans are wallowing in obesity and chronic disease and they want a simple answer to pinpoint the problem.
“We've seen fats vilified before. Carbs have been vilified. These things come in cycles,” said Kris Sollid, a registered dietitian with the International Food Information Council in Washington, D.C. “Now that spotlight is on sugar.”
Sugar gets blamed for many health maladies. But that accusation needs to be put into context, according to researchers and dietitians who say it can be safely enjoyed in moderation, within the limits of a healthy diet.
Not so sweet on sugar
Sugar is a popular bad guy these days.
“If international bodies are truly concerned about public health, they must consider limiting fructose, and its main delivery vehicles, the added sugars (high fructose corn syrup) and sucrose, which pose dangers to individuals and to society as a whole,” wrote a trio of health and obesity researchers from the University of California, San Francisco, in an editorial in February in Nature, an international science journal. They said sugar consumption is linked to disease, is harmful to bodies in ways similar to the consumption of alcohol and should be reduced through taxes and sales limitations.
New York City policymakers followed this line of thinking when they voted recently to ban the sale of certain sweetened drinks in containers larger than 16 ounces.
For many years, studies have explored the connections between sugar and various health ailments. The problem is, studies often contradict each other.
“New studies get headlines, but it takes time for experts to examine them and consider, 'Does this change the way we think?'” said Sollid, who is also the manager of nutrients for the International Food Information Council.
To separate fact from fiction, the IFIC, a nonprofit public education foundation, produced a four-part series on “The Science of Sugars,” for publication in the journal Nutrition Today. The first of the series ran in the May/June issue and the final one is scheduled for the November/December issue. The articles analyze a decade of research to help consumers put new or sensational headlines into a broader context. Much of the report's conclusions contradict some common presumptions about the ills of sugar.
While acknowledging that sugar does contribute to dental cavities, the report basically releases the sweetener from blame when it comes to obesity, Type 2 diabetes and cardiovascular disease.
Evidence linking sugar consumption to obesity is inconsistent and controversial.
In fact, some studies showed that people who consumed more sucrose had lower body weight or fat mass.
Under laboratory conditions, one study found that sucrose consumption contributed to satisfaction and fullness, which reduced subsequent food intake. That study did not address high fructose corn syrup, which is a different form of sugar (See “Defining sugar”), but the study's authors said they believed the effects would be similar.
But other theories suggest that it's high fructose corn syrup in sugar-sweetened beverages that is linked to obesity. Studies haven't been able to prove a cause-and-effect relationship. The American Medical Association issued a policy statement that said high fructose corn syrup doesn't appear to contribute more to obesity than any other caloric sweeteners.
The problem with sugar-sweetened sodas — as well as foods laden with added sugars — is not just the sugar. It's the calories and the fact that Americans consume too much.
There's an assumption that Americans are eating more sugar than ever, but that's not the case, Sollid said. We're just eating more calories.
In 2009, Americans consumed about 440 calories per day from caloric sweeteners, including sucrose and high fructose corn syrup. That's not a big stretch from 1989, when the per capita consumption was 433 calories. However, during that 20-year period, the average daily calorie intake jumped from 2,388 to 2,594.
A 12-ounce soda has about 150 calories, for example. A piece of frosted chocolate cake has 537.
“Do you have room in your diet for those calories? A lot of the concern with sugars is not necessarily about the consumption, it's about over consumption,” Sollid said. If you're physically active and can balance calories burned with calories consumed, a soda on occasion is fine.
Studies clearly show that for each additional soft drink consumed, both body mass and weight increase. But even studies that associate soft drinks with obesity usually include a caveat that obesity is a multi-faceted problem. There could be other factors at play, such as television viewing and less participation in sports, which studies have associated with being overweight.
Diabetes has been on the rise. The Centers for Disease Control and Prevention reports that 11.3 percent of adults over age 20 have diabetes.
Contrary to popular belief, scientists generally agree that sugar is not to blame for Type 2 diabetes, according to the report. Obesity, genetics, ethnicity and inactivity are among risk factors for the disease.
“Eating sugar doesn't cause diabetes. But being obese can increase your risk for that disease. Many things, including sugar, contribute calories,” said Sollid.
Some studies have linked sugar-sweetened beverages with obesity and therefore indirectly with increased risk of diabetes. In the Nurses Health Study, which is among the largest and longest-running investigations on women's health issues, women who increased their consumption of such drinks gained more weight and had more incidence of diabetes than those who drank less soda. However, women who consumed the most sugar-sweetened beverages were generally less physically active, smoked more, had a higher daily caloric intake and lower daily protein intake, putting into question whether sugar is solely responsible for the disease.
Some studies that look for a link to diabetes examine total sugar intake while others differentiate types of or sources of sugar in the diet. Evidence has indicated that the fructose form of sugar reacts with protein molecules in our bodies in a way that may accelerate the aging process and contribute to Type 2 diabetes. Sugar alcohols such as sorbitol and xylitol, on the other hand, may be a better choice for diabetics because their chemical structures don't require insulin for absorption, and don't produce spikes in blood sugar.
The bottom line, according to the report: “The preponderance of evidence shows that total sugar intake is not related to diabetes risk.”
Eating carbohydrates, such as sugars, is not considered an independent risk factor for cardiovascular disease, according to the IFIC report.
However, replacing dietary fats with carbohydrates may increase triglycerides, a type of fat in the bloodstream that can lead to narrowing or hardening of the arteries. Some short-term studies show that high-carbohydrate diets, particularly those high in sugars, increase triglycerides and decrease HDL (good) cholesterol. But again, there are other factors to consider. Increased physical activity and weight reduction can minimize the tendency for high-carbohydrate diets to boost triglyceride levels, the report said.
There's still much uncertainty about how different types of sugar affect cardiovascular health, and more research is called for. Some research points specifically at the fructose form, noting that Americans are consuming proportionately more fructose than other forms of sugars than they used to, and fructose may adversely affect heart health. Fructose is metabolized in the liver, in a metabolic pathway that can lead to an increase in triglycerides, according to the report.
One study compared the effects of glucose and fructose sweetened beverages on 17 obese men and women, finding that triglyceride levels increased in all cases, but the fructose-sweetened beverages resulted in 200 percent higher levels of triglycerides than the glucose-sweetened ones.
The problem with various studies on fructose, Sollid said, is that they look at fructose in isolation, which doesn't accurately represent how people eat, Sollid said. Plus, most study fructose in exceptionally high amounts.
“Fructose doesn't appear in isolation in nature. When you have fructose, you're also finding glucose,” he said. (Both sucrose and high fructose corn syrup are about half glucose, half fructose.) “Fructose wouldn't be the only (sugar) in most products. Fructose can be added to some foods in isolation, like agave syrup, or agave nectar, which would have more fructose content.”
Sugars contribute to food preservation in products like jams and cured ham. They create volume in ice cream and baked goods. They enhance the texture of many foods.
Most notably, sugars can improve the flavor of innumerable food items.
Sugar itself is devoid of vitamins or minerals, but adding it to nutritious foods can make them more palatable, and therefore increase consumption of certain healthy foods.
“It's a lesser-talked-about benefit,” said Sollid. “While (added sugars are) not a source of nutrients or vitamins themselves, they can increase the enjoyment of consumption of good foods, like dairy products, oatmeal, yogurt, whole-grain cereals. These are significant sources of nutrients. Sugar enhances their consumption. When sugars are added, certain foods are more palatable.”
Many researchers have speculated whether adding sugar to products dilutes the nutritional value of the food.
One study found that people who consumed more than 18 percent of their total calories from added sugar didn't meet the recommended daily allowance for many nutrients. But another study found a different kind of finding: For children and adolescents, added sugars in a diet indicated lower consumption of dairy and fruits, but higher intake of grains, vitamin C and and iron. The consumption of sweetened dairy products, such as flavored milk, and sweetened cereals, increases the consumption of calcium, iron and folate.
How much is too much?
There's no true consensus on an upper limit for sugar intake.
Policymakers have considered the question based on the idea that sugars can contribute to excess calories and that they may dilute the nutritional density of a food. But the committee that regularly updates and revises the Dietary Guidelines for Americans has merely said that solid fats and added sugars combined should comprise no more than 5 to 15 percent of a person's daily calories. Solid fats and added sugars currently comprise about 35 percent of Americans' diets.
The World Health Organization says added sugars should not exceed 10 percent of one's total calories, although the organization acknowledges that the recommendation may not be based entirely on science.
The Institute of Medicine Dietary Reference Intakes offers no specific guidelines for added sugars, but recommends that Americans get 45 to 65 percent of their calories from carbohydrates. (People need a minimum of 130 grams of carbohydrates per day for proper brain function.) While sugar is a carbohydrate, Sollid said that's not a license to get half of one's calories from sugar. Most people don't get enough fiber and nutrients. Fruits and vegetables are nutrient-dense carbohydrates which also provide ample sugar for the body to function.
The Academy of Nutrition and Dietetics issued a position paper recently that said consumers can safely enjoy sugars so long as they're within national recommendations for nutrition needs and calories.
“A preference for sweet taste is innate and sweeteners can increase the pleasure of eating,” the paper said.
Sugars occur naturally in a wide variety of fruits, vegetables, milk and dairy products. They are also produced commercially and added to foods.
The term “sugar” most often refers to sucrose, but also includes other forms such as high-fructose corn syrup, fructose and glucose.
The term “added sugar” refers to sugars that are added to foods during processing or at the table.
“Naturally occurring” sugars are those found naturally in foods, such as fructose in fruit, or lactose in milk.
Different forms of sugar we find in our foods include:
Monosaccharides, or simple sugarsGlucose: Found naturally in corn. Glucose is the primary source of energy for the body and the only fuel used by brain cells. Digesting starches (cereals, grains, pastas) yields glucose.
Fructose: Found in fruits, honey and root vegetables. When it occurs naturally, it's found with other sugars such as glucose. Pure fructose is also a sweetener added to foods and beverages.
Galactose: Unique to milk and dairy. Bound to glucose, it forms lactose.
Sucrose: Known as table sugar, it's composed of one glucose unit and one fructose unit. It's found naturally in sugar beets and sugar cane.
Lactose: Found naturally in milk, and sometimes called milk sugar, it's composed of one galactose unit and one glucose unit.
Maltose: Two glucose units. Found in molasses and used in fermentation.
Polyols, or sugar alcohols
Include sorbitol, xylitol, mannitol, maltitol, lactitol, erythritol, isomalt, and others. They have a different chemical structure, are generally not as sweet as sucrose. Sugar alcohols are slowly and incompletely absorbed from the intestine into the bloodstream. They have little impact on blood sugar and can therefore be beneficial to diabetics.
They have fewer calories, and are found in sugar-free candies, chewing gum, baked goods, chocolates, and also oral health products such as cough syrups and mouthwash.
Sugar alcohols occur naturally in some fruits as well as mushrooms and fermentation-derived foods such as wine, soy sauce and cheese.
Corn syrup: Contains either glucose or combinations of glucose and fructose. It can refer to any of several corn-derived products. Corn syrup found in the baking section of the supermarket is most often 100 percent glucose.
High fructose corn syrup: A mixture of glucose and fructose derived from corn. The most common form is 55 percent fructose and 52 percent glucose, and it's most often used commercially.
Source: The International Food Information Council
Sugar and hyperactivity in children
Previous theories and plenty of parents have suggested that eating sugar creates hyperactivity in children.
But they're wrong, according to the last of a four-part series called “The Science of Sugars,” produced by the International Food Information Council and scheduled for publication this winter in the journal Nutrition Today.
Researchers who have analyzed more than a hundred studies on this subject concluded that sugar intake doesn't deteriorate the behavior or cognitive performance in children.
While parents may argue the contrary, it's well-proven that sugar consumption is not linked to hyperactivity in children, said Bend registered dietitian Lori Brizee. Many double-blind studies have tried to tie the two together and found no increased aggression in children's behavior.
But sure, she said, kids may behave unpleasantly under circumstances that may include, among other factors, sugary foods.
“Sometimes kids aren't going to feel good when they just eat a bunch of sugary stuff and are not getting what (healthy food) they need,” Brizee said. When a kid's blood sugar bounces up and down, they might feel tired and act crabby.
Or, take Halloween or a birthday party for example. Yes, kids are probably eating a lot of sugar. They're also wearing costumes, staying up late, feeling excited about a party atmosphere. “Kids are hyper,” under that entire set of circumstances, Brizee said.
But when researchers control for all the extra factors, feed kids sugar and observe their behavior, they don't find that hyperactive behavior results from just sugar consumption.