Not surprisingly, the conflicting results from these studies have set off a heated debate among scientists over the safety of fructose-containing sweeteners. Some researchers believe that the difference in the way the body handles glucose and fructose is responsible for many of the negative effects associated with fructose. As noted earlier, fructose is not absorbed into fat, muscle, and other body cells from the bloodstream but instead goes to the liver, where it forms triglycerides and LDL cholesterol. These lipids then enter the bloodstream, where they may trigger complex processes that make the body less sensitive to insulin and set the stage for the development of diabetes and other disorders.
Other scientists are skeptical of findings that suggest negative effects from fructose on blood pressure, weight control, and blood lipid levels. They note that most of the data supporting these findings are from studies with a short duration and a very small sample size. Some suggest that errors in measurement of triglycerides and body fat could have led to misleading or inaccurate results. Skeptical researchers also doubt that the unique properties of fructose can explain the tremendous rise in obesity and related health conditions in the United States in recent years.
Questions raised
Needless to say, the contradictory and sometimes confusing data presented by these studies raise a number of questions. One pattern seen across these studies is that while obese people tended to experience negative effects from fructose on blood pressure, blood lipid levels, and appetite, lean and healthy people often did not. It might therefore be useful to further explore the role that genes and family history play in shaping reactions to fructose-containing sweeteners.
Another important point about these studies is that they looked at many different forms of fructose. Although many examined high-fructose corn syrup in beverages, others used prepared solutions containing varying percentages of fructose. As a result, these studies put very different questions to the test, such as: Is HFCS worse for the body than table sugar? Is fructose worse than glucose? What happens when extra fructose is simply added to the diet?
To understand the possible role that fructose and HFCS play in the development of obesity and related diseases, it will be important for future studies to ask a clear question and then choose their participants and methods accordingly.
Limiting all sugars
In light of the studies conducted to date, most scientists agree that there is currently no convincing evidence of a direct link between HFCS and obesity or other health problems. The consensus, instead, is that the real culprit appears to be consumption of too many calories from all food sources. Americans’ high intake of all types of sugar and other refined carbohydrates, in particular, may be the main driver of obesity and other chronic health problems.
Recognition of the role of sugar in the development of obesity has prompted the US Department of Agriculture (USDA) to make recommendations about sugar consumption. As part of its Dietary Guidelines for Americans, 2010, the agency’s Center for Nutrition Policy and Promotion urges everyone to choose foods and beverages with few added sugars. Because added sugars are not listed separately from total sugars on product labels, the guidelines also encourage consumers to check the ingredients list on labels for sources of added sugar.
The American Heart Association goes even further in its recommendations for added sugar intake: It advises men to limit their consumption to 150 calories a day (about 9 teaspoons of sugar), and women to limit theirs to 100 calories a day (about 6 teaspoons of sugar).
Americans currently ingest an astonishing 130 pounds of sugar a year, or an average of 38 teaspoons each day, so meeting these recommendations on a nationwide level will be difficult. On an individual level, dietary changes are best accomplished gradually over time — and cutting back on added sugars is no exception. Here are some tips to get you started:
