A few weeks ago, when my sisters were visiting, we spent a day at Disneyland and I finally got up the courage to ride Space Mountain. I’ll admit, it was way more fun and way less scary than I was anticipating (phew!) But while riding roller coasters might be fun, it is certainly not fun, or healthy, when our blood sugar is on a roller coaster.
I think many people are familiar with the feeling . . . it seems you’ve hit a wall, so you eat a “quick fix” snack (like a candy bar or bag of pretzels), and the energy comes rushing back! But before long, you’re hitting that wall again, your energy is low and you feel exhausted, maybe even a bit shaky. While there are certainly many different lifestyle causes of low energy throughout the day, this particular high and low cycle is indicative of what is happening to your blood sugar levels.
You see, when we eat foods that quickly and drastically raise our blood sugar, we get a surge of insulin to help bring all that sugar into our cells. However, when this insulin response is produced for very high blood sugar, it tends to overcorrect, leaving us hypoglycemic (that is, with not enough sugar in our blood stream) and craving another “quick fix” snack . . . in short, we end up on a roller coaster of high highs and low lows.
When our blood sugar is on a roller coaster, it spells disaster for our health. Not only does this cycle involve snacking on high calorie, nutrient poor sugary foods and more often than not overeating (both leading to weight gain), it’s also damaging on a cellular level. As explained by Buyken et al in an article published in the American Journal of Clinical Nutrition in 2014, “excessive postprandial blood glucose excursions are considered to yield nitric oxide generation, which in turn combines with superoxide to produce peroxynitrite—a potent long-lived pro-oxidant molecule.” In short, a diet including foods which cause blood sugars to spike causes chronic low grade inflammation and oxidative stress, which have been implicated in metabolic syndrome, cardiovascular disease, dementia, certain types of cancer, type 2 diabetes, stroke, and depression.¹
Enter the glycemic index.
Introduced in the early 80s, the glycemic index (GI for short) is a way to measure the blood sugar response elicited by individual carbohydrate foods. In his book Nutritional Medicine, Dr. Alan Gaby defines the glycemic index as “the incremental area under the 2-hour glucose curve after ingestion of 50g carbohydrate from a test food, divided by the corresponding area after consumption of a control food (either white bread or glucose), multiplied by 100.”² The scale ranges from 0-100, with foods higher on the scale (i.e. high glycemic) causing a quick increase in blood sugar and insulin, and foods lower on the scale (i.e. low glycemic) associated with a lesser and more gradual blood sugar response.
In theory, basing our food choices off of the glycemic index is a simple way to stay proactive in managing our health. In practice, however, it may not be that easy. You see, the glycemic index of a food is influenced by the form of food, its acidity, the type of starch in the food, and the amounts & types of protein, fat, and fiber in the food.³ Because of the various factors impacting a food’s GI rating, some GI ratings may seem counterintuitive and unexpected. An apple, for instance, has a GI rating of about 39, while watermelon is rated much higher, at about 72. Peanut m&m’s have a GI score of 33, while honey has an average score of 61 (read more here and here). So, without memorizing the GI score for every single food, closely following a low glycemic diet may require a bit more research and planning than my go-to and recommended method (i.e. just eat real food)!
At the end of the day, the glycemic index is a useful tool for staying healthy. It becomes even more useful when taking into account the glycemic load (the GI rating of a food multiplied by the carbohydrate content of a serving of said food). It might be a bit tricky to navigate, but trying our best to consume a diet of whole & mostly low glycemic foods will most definitely serve us in the long run!
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1. Buyken, A., Goletzke, J., Gesa, J., Felbick, A., Cheng, G., Herder, C., & Brand-Miller, J. (2014). Association between carbohydrate quality and inflammatory markers: systematic review of observational and interventional studies. The American Journal of Clinical Nutrition, 99(4), 813-833. Retrieved from http://ajcn.nutrition.org.uws.idm.oclc.org/content/99/4/813.long
2. Gaby, A. (2011). Nutritional Medicine. Concord, NH: Fritz Perlberg Publishing.
3. Jones, D. (2010). Textbook of Functional Medicine. Federal Way, WA: The Institute for Functional Medicine.
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