Since sugary drinks are the leading source of added sugar in the American diet, and it’s quite easy to take in lots of calories in beverages without much effect on satiety, a lot of the harm done by consuming sugary drinks can be explained by the weight gain associated with their consumption.
But there’s another school of thought, and growing supporting research, that believes that sugars -- and especially the fructose component of sweeteners -- are especially harmful to our health, and have direct adverse effects on fat metabolism and inflammation.
Our metabolism on sugary drinks
A previous study from the University of California at Davis showed that drinking 25 percent of daily calories in fructose for 10 weeks increased triglycerides and cholesterol and caused insulin resistance in people, while drinking the same amounts in glucose didn’t. And while both the fructose and the glucose groups gained weight during the study, the fructose group gained more belly fat.
Indeed, a concerning finding, but drinking 25 percent of calories in fructose is something very few of us do (although many teens do take in about 20 percent of their calories in added sugars, and do so daily for many years).
Now, a new study, led by Isabelle Aeberli, and published in the American Journal of Clinical Nutrition, looked at 29, young, healthy, non-overweight men, who drank more reasonable amounts of sugary drinks containing different levels of fructose, glucose or sucrose (which is a glucose/fructose mix).
(Quick reminder: Our foods and drinks are usually sweetened with sucrose (table sugar) or high fructose corn syrup (HFCS); both types of sweeteners are a combination of the simple sugars glucose and fructose.)
Each participant spent 3 weeks on each of the following 6 beverage regimens, with a 4-week washout between interventions:
- Medium fructose: 40 g of fructose a day
- High fructose: 80 g of fructose a day
- Medium glucose: 40 g of glucose a day
- High glucose: 80 g of glucose a day
- High sucrose: 80 g of sucrose a day
- Control: No sugary drinks at all
Just to put the sugar content in perspective: The medium sugar interventions are equivalent to drinking 1 can (12 oz.) of coke/day; the high sugar interventions are equivalent to drinking 2 cans (24 oz.) of coke/day.
The experiment lasted about 44 weeks; here are some of the main findings:
- Waist-to-hip ratio increased in the medium fructose, high fructose and high sucrose interventions (higher waist-to-hip ratios indicate abdominal obesity, which is associated with an increased risk of heart disease and type 2 diabetes)
- Fasting glucose levels increased in all five sugary drink interventions
- C-reactive protein, a marker of inflammation, increased in all 5 sugary drink interventions, with the highest values seen in the high fructose intervention. Inflammation is a key factor in the development of both heart disease and type 2 diabetes
- There was a reduction in large, buoyant LDL particles when participants were consuming fructose drinks (high and medium fructose and high sucrose interventions). A regular lipid profile measures only total LDL, which didn’t change between interventions; we now know that there are subclasses of LDL, and the smaller LDL molecules pose more risk and have a higher tendency to block arteries. The large buoyant LDL is, as the name implies, flexible and bouncy, and causes less lumps and blocks.
- All sugary drink interventions lead to some increase in caloric intake
- Leptin (a hormone that regulates appetite and metabolism) increased in the medium and high glucose interventions, but not in the fructose and sucrose interventions
What can we learn from this study?
The first conclusion we can draw from this study is that fructose does seem to cause more damage than glucose – fructose leads to lipid abnormalities and more belly fat accumulation. On the other hand all sugary drink regimens, including the moderate glucose exposure, had pretty unhealthy results: all 5 interventions increased markers of inflammation and increased caloric intake.
The practical, real-life understanding is that all sugary drinks, even in what many would consider “moderate” amounts, seem to have a measurable undesirable effect after as little as 3 weeks.
As far as I know there are no popular drinks in the market sweetened by glucose; practically all forms of caloric sweeteners used in food processing are a glucose/fructose mixture. Cane or beet sugar are sucrose (table sugar), which is a two-sugar molecule with exactly 50 percent glucose, 50 percent fructose. HFCS is about 45 percent glucose, 55 percent fructose. Fruit juice concentrate's sugar composition will depend on the fruit source: Apple juice concentrate is about 30 percent glucose, 70 percent fructose, while orange juice concentrate is about 50 percent glucose 50 percent fructose. Agave syrup is about 70-75 percent fructose.
All sugary drinks contain fructose, and if this study’s findings are confirmed in larger and repeated studies, there’s reason for worry.
Full disclosure: I’m vice president of product development for Herbal Water, where we make organic herb-infused waters that have zero calories and no sugar or artificial ingredients. I’m also a pediatrician and have been promoting good nutrition and healthy lifestyle for many years.
Reposted as part of Food Renegate's Fight Back Fridays.