What is the Glycemic Index?
The glycemic index (GI) is a measure of how quickly a food causes our blood sugar level to rise. The food is ranked on a scale from 0 to 100. Foods with a high GI are quickly digested and absorbed causing a rapid rise in blood sugar, which often, but not always, are highly processed carbohydrates and refined sugars. For example, a saltine cracker has a GI of 72, whereas a skinless baked potato contains a GI of 94!
Foods with a low GI are digested and absorbed at a slower rate and result in a slower rise in blood sugar levels. Low GI foods are typically higher in fiber, protein, and/or fat. Foods with very little to no carbohydrate (meats, fish, eggs, and avocados) do not have a GI value.
In other words, no carbohydrates = no GI = no effect on blood sugar, insulin, and ketosis.
Choosing foods with a low GI can make it easier to lose weight and feel satiated. Diets focused on low GI foods have been shown to improve insulin resistance, and lower glucose, cholesterol, and triglyceride levels in people with type 2 diabetes.
Glycemic Index and keto sweeteners
Luckily, low-carb, high-fat diets like the ketogenic diet are centered around foods with a very low GI! But one particular food type continually raising eyebrows is alternative sweeteners. Although the majority of these type of sweeteners have a very low GI, they are by no means created equal (pun intended). 😉
Generally, there are three classifications of sweeteners: natural, sugar alcohols, and synthetic (a.k.a. artificial). Below is a breakdown of common sweeteners and where they fall on the GI. Note that similar to honey and agave, others like erythritol and stevia are also found in nature. That said, I recommend not using the natural sweeteners honey, agave, and maple as these will elevate blood sugar, insulin, and kick you out of ketosis.
What should you look for on sweetener labels?
When you purchase a sweetener, aim for the pure form rather than one with fillers, like Splenda and Stevia in the Raw. Avoid being swayed by the product name, and check the ingredients on the packaging. If you see fillers like maltodextrin or dextrose, put it back on the shelf. These fillers are hidden carbohydrates that will spike your blood sugar and potentially result in lower ketones.
Which sweeteners are the best to avoid blood level spikes?
By a long shot, my favorite keto-friendly sugar substitutes are Stevia, erythritol, and monk fruit. These sweeteners are all naturally derived, have little to no effect on blood sugar and insulin, and have minimal negative gastrointestinal or laxative side-effects (which can be experienced with some sugar alcohols). In addition, these sweeteners have not been shown to negatively affect the good bacteria in the gut, which is a concern with synthetic or artificial sweeteners.
Allulose is also at the top of the list, but it comes with a high price tag. Some small studies have shown that Allulose may even help suppress the glycemic response when it is consumed with other types of glycemic foods.
Should I use sweeteners on a keto diet?
Most people who follow a keto diet often find the sweet cravings go away, and many don’t use sweeteners at all! However, if you do use sweeteners, choose natural alternatives with the lowest GI, and avoid (or limit) artificial sweeteners as much as possible. If your goal is weight loss, even natural, zero-carb sweeteners may impair your progress as these can result in cravings and overeating. If you find you have stalled, try eliminating all sweeteners for a couple of weeks and see if this helps.
Otherwise, choose your sweeteners wisely and keep rockin’ that keto lifestyle!
Tara Finnerty RDN, CSP, CD—is a ketogenic specialist and fat-fueled enthusiast. Tara is a registered dietitian in Utah and owner of Sugar House Nutrition LLC. Her aim is to provide nutrition support for people wanting to reap the many health benefits of the ketogenic (keto) diet. Her expertise in the keto diet was initially working with children who have uncontrolled epilepsy. Tara supports nutrition diversity and works toward helping people find an individualized approach to make healthy eating sustainable.