Understanding Glycemic Index of Grains and Strategies for Healthier Eating

Glycemic Index of grains

The glycemic index (GI) measures how quickly carbohydrates are digested and absorbed into the bloodstream as glucose.

Grains are complex carbohydrates or starch, with many glucose molecules joined together. So one might expect that they take a longer time to digest compared with simple sugars that have just one or two sugar molecules joined together.

The Dual Boosters: Starch Content and Nature in Grains

But no. Grains are like "twin-booster rocket fuels" that very quickly send your blood glucose sky high. The first booster is the high starch content. The second booster is the nature of the starch. Grain contains mostly a type of starch called amylopectin A, which is the very efficiently digested and rapidly absorbed into the bloodstream. Wheat, in particular, contains about 75 percent amylopectin A.
In comparison, other starchy foods like potato and banana contain amylopectin B, which takes a longer time to digest. The starch in beans is amylopectin C, which takes an even longer time to digest. These foods do not contain as much starch as grains to begin with. So grains not only have a high GI but also a high GL. When grains are combined with sugar, this problem is further compounded.
The following table gives the GI of various grains and flour products:

            FOOD GLYCEMIC INDEX (GI)

FOOD                                                 Glycemic Index (GI) 

Brown rice                                                         55
White rice                                                          72
100% wholewheat bread                                 51
Wholemeal bread                                             69
White bread                                                      71
Millet                                                                  71
Corn                                                                   60
Whole grain Oats                                            49
Whole grain rye bread                                    41
Barley Pearl                                                      28
Pasta (Whole Wheat)                                     42
Pasta (Refined)                                                50
White Sugar                                                     70

Strategies to Counteract the High GI of Grains

To counter the high GI of grains, you should eat them with foods that contain fats, proteins, vitamins, minerals and other nutrients. These will slow the digestion of grains and the absorption of glucose into the bloodstream.
Pasta's misleading GI: Pasta has a relatively low Gl of 50 or below. This is because pasta is made with durum wheat, which has a higher protein content. However, the low GI is misleading. It reflects a slow rise in blood glucose during the first two hours after eating pasta. But the blood glucose continues to rise to quite high levels for the next four to six hours. Pasta is thus not recommended for those with obesity and diabetes.