The glycemic index (GI) has always been surrounded by controversy within the U.S., whether it is included with nutrition guidelines for diabetes or weight loss recommendations. However, recent research is showing that there certainly is a place for its use and healthcare professionals have an obligation to give practical advice to individuals who are interested in incorporating this meal planning method into their lives.

The discussion regarding GI was first published in 1981 by its creators David Jenkins, MD, Thomas Wolever, and their colleagues at the University of Toronto (1). This study proved that low glycemic index foods do have a positive impact on glucose control. They also speculated this method of meal planning could be useful for post gastric surgery patients and those with hypertriglyceridemia. In my opinion, this paper essentially laid the groundwork to proceed with all subsequent research.

So, it is no surprise that many of the nutrition guidelines for other countries do include the use of GI as a meal planning method (2-5).  Diabetes Victoria took it one step further and included suggestions to use low GI guidelines for catering events as well (6). In the most recent American Diabetes Association nutrition guidelines, it was also echoed from previous ADA Clinical Practice Recommendations that GI can be a useful tool (7).  A review article was also published in 2013 as background for the Nordic Nutrition Recommendations summarizing the benefit of dietary fiber and the use of GI for weight loss (8).

In June 2013, the Nutrition Foundation of Italy and Oldways sponsored a two-day International Scientific Consensus Summit on glycemic index, glycemic load (GL) and glycemic response. In addition to the plethora of research highlighted promoting GI and GL, the summit also created a draft scientific consensus statement (9) that included 20 statements, which included:
•    Reducing postprandial glucose is beneficial
•    Low GI can improve glycemic control
•    Low GI could be helpful with CVD and weight loss
•    More comprehensive food composition tables need to be created (9).

The majority of the presentations are available for review on the website via the link below.

Most recently, several articles have been published highlighting the benefits of GI. Researchers in Spain evaluated the effect of dietary GI on weight loss, satiety, glucose and insulin metabolism, lipids, and inflammation by comparing a low GI diet, high GI diet and low-fat diet. The results showed that the low GI diet reduced weight more effectively than low fat.  It also improved insulin resistance (10).

A prospective study was also published examining the effect of GI and GL on the risk of type 2 diabetes. The researchers analyzed 3 cohorts, creating a new meta-analysis, which provided further evidence that higher GI and GL are associated with increased risk of type 2 diabetes (11).  Several recent papers have also proved the benefit of low GI with type 2 diabetes and those with a history of gestational diabetes (12-15). The conclusions from each were essentially the same: low GI and GL can improve blood glucose response. One did caution that GI should be part of the meal planning, not the entire meal plan tool since carbohydrate and energy intake is important as well.

With the continuance of mounting evidence to incorporate low GI in our meal planning methods, the question is how? The answer will depend on the level of understanding on the patient’s part. For many, using GI as a meal planning tool may be a step-by-step process to make them understand that our own dietary guidelines promote many low GI items, without actually spelling it out. Our first step is to firmly plant the general healthy eating guidelines:
•    Increase fiber
•    Choose whole foods rather than processed
•    Increase fruits and vegetables – limit over-ripened fruit
•    Do not focus so heavily on the GI number itself, but if eating a high GI food, incorporate it into a meal with lower GI foods
•    Do not overcook pasta
•    Still focus on the portion size eaten
•    Follow the MyPlate method for portions

Once they can incorporate these simple guidelines into their meal planning, then they can be ready to delve a little deeper into GI and GL.

A paper was published in the Brazilian Journal of Nutrition that discussed the use of glycemic index in nutrition education (16).  The paper highlighted a GI table that was created by researchers from the University of Sao Paulo that contains some of the most commonly prepared foods in Brazil.The paper emphasized the need to use tables that are specific to the population, which brings up the point that when we are choosing resources for our patients, we do want them to be culturally specific.

In the next blog about GI, I will focus on some of the handouts and resources that can be used to effectively teach GI.

References
1)  Jenkins DJ Wolever TM , et al. Glycemic Index of foods: a physiological basis for carbohydrate exchange.  Am J Clin Nutr. 1981 Mar;34(3):362.

2) Canadian Diabetes Association (CDA) Guidelines.

3) Dietitians Association of Australia (DAA) Guidelines.

4) Diabetes UK.

5) European Association for the Study of Diabetes (EASD) Diabetes and Nutrition Study Group (DNSG).

6) Diabetes Victoria.

7) American Diabetes Association Nutrition guidelines.

8)  Overby NC et al. Dietary fiber and the glycemic index: a background paper for the Nordic Nutrition Recommendations 2012Food and Nutr Res. 2013; 57.

9)  2013 GI Summit.

10) Juanola-Falgarona M et al. effect of the glycemic index of the diet on weight loss, modulation of satiety, inflammation, and other metabolic risk factors: a randomized controlled trial.  Am J Clin Nutr 2014;100:27.

11) Bhupathiraju SN et al. GLycemix index, glycemic load, and risk of type2 diabetes: results from 3 large US cohorts and an updated meta-analysis. Am J Clin Nutr. 2014;100:218.

12) Farvid et al. Glycemic index, glycemic load and their association with glycemic control among patients with type 2 diabetes. Eur J Clin Nutr 2014;68:459.

13) Greenwood DC et al. Glycemic index, glycemic load, carbohydrates and type 2 diabetes. Diab Care 2013;36:4166.

14) Oba S et al. Dietary glycemic index, glycemic load and incidence of type 2 diabetes in Japanese men and women: the Japan public health center-based prospective study. Nutrition Journal 2013;12:165

15) Shyam S et al. Low glycemic index diets improve glucose tolerance and body weight in women with previous history of gestational diabetes: a six months randomized trial. Nutrition Journal 2013;12:68.

16) Candido FG et al. Use of the glycemic index in nutrition education. Revista de Nutricao, Campinas 2013;26(1):89.