The Glycaemic Index (or GI) ranks carbohydrates in food on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating:
- Low GI foods raise blood glucose more slowly and cause a smaller rise in insulin levels – eg. beans, legumes, non-starchy vegetables, sweet potatoes, whole grain breads, cereals, most fruits (except bananas, melons, pineapple, raisins);
- High GI foods cause a fast/ large rise in blood glucose levels and a resultant insulin spike – eg. vegetables (potatoes, corn), white/ processed breads, snacks (chips, popcorn, pretzels), alcohol, anything sweet (honey, molasses)
The above is not an exhaustive list. Google “high GI” and “low GI” foods for more information.
Multiple health organisations recommend the intake of low GI foods as a way to control blood sugar levels and control/ treat disease (eg. the Australian Diabetes Council, American Diabetes Association, Mayo Clinic, Harvard School of Public Health to name a few). This supposedly results in health benefits – reducing diabetes, lowering risk of heart disease, curbing inflammation, and helping with weight loss.
It was definitely an Asian-victory-sign moment when I read a recent study in JAMA which interestingly found no major benefits associated with a low GI diet – specifically, no significant effect on insulin sensitivity, systolic blood pressure, or cholesterol (both good and bad). Additionally, high dietary carbohydrate (compared with low) increased ‘bad’ cholesterol, whereas the low carbohydrate diets actually decreased triglycerides.
Then why do most major guidelines recommend significant portions of complex carbohydrates in the diet, huh?
Sacks FM, Carey VJ, Anderson CA, Miller ER 3rd, Copeland T, Charleston J, Harshfield BJ, Laranjo N, McCarron P, Swain J, White K, Yee K, Appel LJ. Effects of high vs low glycemic index of dietary carbohydrate on cardiovascular disease risk factors and insulin sensitivity: the OmniCarb randomized clinical trial. JAMA. 2014 Dec 17;312(23):2531-41.