Glycemic Index - Alternatives and Related Scales

Alternatives and Related Scales

The glycemic index does not take into account other factors besides glycemic response, such as insulin response, which is measured by the insulin index and can be more appropriate in representing the effects from some food contents other than carbohydrates.

Although the Glycemic Index provides some insights into the relative diabetic risk within specific food groups it contains many counter-intuitive ratings. These include suggestions that bread generally has a higher glycemic ranking than sugar and that some potatoes are more glycemic than glucose.

More significantly studies such as that by Bazzano et al. demonstrate a significant beneficial diabetic effect for fruit compared to a substantial detrimental impact for fruit juice despite these having similar “Low GI” ratings.

From blood glucose curves presented by Brand-Miller et al. the main distinguishing feature between average fruit and fruit juice curves is the maximum slope of the leading edge of 4.38 (mmol/L)/hr for fruit and 6.71 (mmol/L)/hr for fruit juice. This slope represents the maximum rate at which glucose accumulates in the blood stream or MGR and is the rate at which glucose entry into the blood exceeds the ability of the body to remove it.

Extending the assessment from fruit to simple homogeneous solids consisting largely of similar carbohydrates reveals that other diabetic-beneficial foods such as Pasta, low GI white bread and low GI rice also have a MGR around or below 5.0 (mmol/L)/hr. Homogeneous solids associated with high diabetic risk such as potatoes and high GI bread however are observed to have a MGR above 6.0 (mmol/L)/hr.

As there is a clear relationship between the MGR and GI for homogeneous solids this leads to the alternative concept of a MGR Index. Although the MGR and GI give consistent ratings for homogenous solids, carbohydrate liquids including fruit juice and readily dissolvable sugars such as refined sucrose are highly glycemic using the MGR criteria. As processed carbohydrates are largely a combination of homogeneous solids and sucrose these are also determined to be significantly more glycemic using the MGR as a benchmark.