April 11, 2012
Kimber Stanhope, PhD, RD, a project scientist in the Department of Molecular Biosciences, discusses surprising research results on "60 Minutes."
Stanhope offers the following background information about her studies:
Previous study: We studied 32 men and women, all 40 years or older, all overweight. We divided them into 2 groups. For 10 weeks, one group consumed 25% of their calorie requirement as beverages sweetened with glucose. For the other group, the beverages contained fructose. We found, that at the end of the 10 weeks, the 2 groups had gained the same amount weight, about 3 pounds. However, the group that drank the fructose beverages exhibited many detrimental changes that are associated with increased risk for cardiovascular disease and diabetes. These include: 1. increased blood levels of unfavorable fats, 2. decreased insulin sensitivity, 3. increased amounts of the fat tissue that surrounds the internal organs, 4. activation of the pathway by which sugar is turned into fat. None of these changes were seen in the men and women who drank the glucose beverages. These results were published in the Journal of Clinical Investigation (Stanhope, 2009).
This paper was recently described by the JCI editor as being one the 3 most accessed clinical papers published by JCI in the last 5 years.
Why are these results important?
There are a number of research papers reporting that people who eat high sugar diets are more likely to develop cardiovascular disease and diabetes than people who eat less sugar. The sugars that we eat, sucrose and HFCS, are composed of 50% or more fructose. Our results showing that a high fructose diet increases risk factors for cardiovascular disease and diabetes suggest that fructose is the reason why we see a connection between high sugar diets and these diseases.
Our results also show that 2 diets that had identical effects on weight gain, had markedly different effects on risk factors for cardiovascular disease or diabetes. This suggests that it is not just excess calories and excess weight gain that promotes the development of cardiovascular disease and type 2 diabetes. The source of the excess calories is important too.
Current study: The results of previous study led to our current study in which we are investigating the effects of consuming fructose as it is most commonly consumed in the American diet--and this is, of course, high fructose corn syrup (HFCS) and granulated sugar which is sucrose. We are studying 200 men and women, age 18-40, both normal weight and overweight, who for 2 weeks consume sweetened beverages. Depending on the experimental group assignment the beverages may contain 25% of energy requirement as HFCS, sucrose, glucose or fructose. Or they may contain 0%, 10%, or 17.5% of energy requirement as HFCS. Prior to drinking their assigned sweetened beverages, each subject lives at our clinical research center for 3 ½ days while we conduct many experimental tests, including all day and night blood collections. During this time they consume standardized low sugar diets that are high in complex carbohydrate, mainly bread and pasta. They then live at home and consume their usual diet along with one of their assigned beverages at each of their 3 meals. 13 days later they return the clinical research center for another 3 ½ day stay. All the same experimental tests are performed while the subjects consume standardized diets in which the calories from the bread and pasta are replaced with the calories in their assigned sweetened beverage.
Early results from this study were recently published in the Journal of Clinical Endocrinology and Metabolism (Stanhope, 2012). They show that blood concentrations of LDL-cholesterol and other lipids associated with increased risk for CVD were increased in the men and women who drank fructose or high fructose corn syrup beverages. These changes did not occur in the men and women who drank glucose beverages.
This is important direct experimental evidence suggesting that the association between high sugar diets and cardiovascular disease may be due to cause and effect, with the high sugar diet being the cause.