1 November 2014

Q&A with Prof. Jennie Brand-Miller

Prof Jennie Brand-Miller answers your questions. 

Why don’t you use the terms simple and complex carbohydrates anymore?
Research on the glycemic index over the past 30+ years has shown us that using terms like “simple” or “complex” tells us nothing about how the carbohydrates in the foods and beverages we consume affect our blood glucose levels. And for people with diabetes who must manage their BGLs, that’s what matters.

For many years, the nature of carbohydrates was described by their chemical structure. They were either simple or complex and it was all about size. Sugars were simple and starches were complex. Why? Well sugars were small molecules and starches were big ones. From this, it was assumed that big starch carbohydrates would be slowly digested and absorbed and would therefore cause only a small and gradual rise in blood glucose levels. So they were called “complex” and this implied healthy. Smaller sugar carbohydrates were assumed to be digested and absorbed quickly, producing a rapid increase in blood glucose simply because they were small. So we called them “simple” and gave the impression that they were not so good for us.

GI Graph

Then along came David Jenkins and Tom Wolever’s ground-breaking research on the glycemic index. It challenged these assumptions with real science. It showed us what actually happens in our bodies with real foods in real people and blood tests (something that had never been done before). It showed us that the rise in blood glucose after meals cannot be predicted on the basis of molecule size or chemical structure. In other words, the old distinctions between starchy foods (complex carbohydrates) and sugary foods (simple carbohydrates) had no useful application when it came to blood glucose levels – and all of the health issues that relate to them. The GI is the only way you can rank the glycemic potency of the carbohydrates in different foods exactly as they are eaten.

Professor Jennie Brand-Miller (AM, PhD, FAIFST, FNSA, MAICD) is an internationally recognised authority on carbohydrates and the glycemic index with over 250 scientific publications. She holds a Personal Chair in Human Nutrition in the Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders and Charles Perkins Centre at the University of Sydney. She is the coauthor of many books for the consumer on the glycemic index and health.