That Diet Coke isn't so diet anymore

While everyone is working on their New Year's resolutions for 2012, either making them or not breaking them, I thought it would be a good time to write about a trio of articles on sugar and artificial sweeteners and their respective health consequences. A piece published in New York Times magazine several months ago raised the alarm on the extreme health detriments of our sugar habits. Author Gary Taubes cited Dr. Robert Lustig, a researcher in pediatric obesity and hormone deficiencies, as promoting the idea that sugar, not fat, is the main cause for the dramatic rise in type 2 diabetes, hypertension and other "western diet" diseases seen in the last 30 years. These particular detriments stem from the way our bodies metabolize fructose (which makes up half of the refined sugar molecule sucrose), as opposed to pure glucose, which makes up the other half and is found in foods such as potatoes and white bread.

Glucose is metabolized by all cells in the body, whereas fructose is primarily processed by the liver. If the liver cannot adequately break down the sugar (both fructose and glucose) it receives into energy, it is converted into fat. This is more likely to occur if the liver becomes overloaded by the fructose in sucrose solutions, such as in high fructose corn syrup which has a greater concentration of fructose to glucose. The more and faster the body receives the fructose the more likely this is to happen. Therefore, drinking a sugary beverage, such as soda or even fruit juice, results in an even greater spike in fructose as it reaches the liver much more quickly. These drinks place a greater strain on the body than a raw piece of fruit, a "pure" form of fructose, which contains fiber and is digested much more slowly. This failure to break down sugar and the subsequent rise in liver fat is believed to be at the root of insulin resistance, the main underlying deficiency in metabolic disorders such as type 2 diabetes and heart disease.

It is undeniable that as our sugar consumption increases, so do our rates of obesity, diabetes and heart disease. Currently the average American consumes roughly 90 pounds of added sugar a year, and recently non-sugar sweeteners have been proposed as an alternative to sugar and high-fructose corn syrup to help reduce these rates. However two studies from the University of Texas: San Antonio presented at the American Diabetes Association's Scientific Sessions suggest that these changes might not provide any real benefit.

The first, a longitudinal health study, measured participants' waist circumference over a ten-year period. They discovered that diet soda drinkers had an almost 70% increase in waist circumference over this time, and those who reported drinking more than two diet soft drinks every day had waist circumference increases 500% greater than individuals who did not consume any diet drinks. These results remained even after controlling for variables such as starting circumference, diabetes, age, sex, smoking status, physical activity levels, and neighborhood of residence.

The second study assessed the effect of aspartame on a high fat diet in mice. One group received food chow with added corn oil and aspartame, the other just the additional corn oil. The group that consumed the extra aspartame had significantly higher glucose levels, but similar insulin levels than the mice who only received the high fat diet. This signifies severe consequences of a fake sweetener diet on diabetes, as blood sugar levels were elevated but insulin (which lowers blood sugar) was not compensatorily raised. This suggests that diet sodas and other foods made with fake sugar could actually lead to an increased risk for developing type 2 diabetes compared to a high fat diet alone.

So if anyone is still looking for a resolution this New Year, perhaps try cutting back on your soda consumption, both regular and diet. Your liver will thank you.

Dana Smith

PhD student in Experimental Psychology at the University of Cambridge