Is My Coconut Water Blood-Sugar Friendly?

Author: Rachel Selva

INTRODUCTION
Coconut water is a hydration drink of choice for many people, including me. I like it because it hydrates me after a tough workout, and it tastes really good too! I was recently exploring the nutrition facts on the back of the bottle (as a curious exercise physiology student is bound to do), and I noticed one of the ingredients: organic erythritol. The claim on the back of the bottle states that “Erythritol carbs have no calories or effect on blood sugar.” I find this interesting, because as a type 1 diabetic, I always look to see if I need to give insulin for a meal or beverage. And looking at the carbohydrate content on the back of my coconut water bottle showed me that with 9 grams of carbohydrates per serving and 18 grams per bottle, I would indeed need insulin. So this question came to mind: If erythritol carbohydrates have no effect on blood sugar, then why do I give insulin to drink my coconut water?

INVESTIGATION
After some investigation, I found some interesting information on the calorie and carbohydrate content in erythritol. Erythritol is classified as a sugar alcohol. Because the human digestive system cannot break down sugar alcohols, it is absorbed into the bloodstream and mostly passed out in the urine, with a small amount passed in the feces (Gunnars, 2018). So, while erythritol is classified as a carbohydrate, it still has no effect on calories taken in or on blood sugar, because it is not absorbed by the body. And even though it does contribute to the total carbohydrate content of whatever it is added to, the fact that erythritol is not absorbed gives it a net carbohydrate content of zero. The net carbohydrates of a food are calculated by subtracting the carbohydrates that come from sugar alcohols and fiber from the total carbohydrate content on the nutrition label. Erythritol has about 4g of carbohydrate per tsp, but since it passes right through the body without being absorbed, it has a net carbohydrate content of zero (Miller, 2018). Since carbohydrates are the main cause of a rise in blood sugar, erythritol’s zero net carbohydrate content suggests that it would have no effect, and cause no rise in blood sugar.
In order to find some real proof of erythritol’s lack of effect on blood sugar, I researched some scientific studies. In a study by Ishikawa et al., a 14-day oral administration of erythritol to 5 subjects with diabetes showed no adverse effect in blood sugar control, suggesting that erythritol does not affect blood sugar and would not need an insulin injection when ingested (Ishikawa et al., 1996). This suggests that instead of sugar, erythritol is an excellent option for a blood-sugar-friendly sweetener for diabetics.
In another study by Noda et al., they investigated the effect of erythritol on the blood sugar and insulin levels of healthy subjects, rather than diabetic subjects. This is a helpful comparison because unlike diabetic patients, with whom you can only measure a rise in blood glucose (since there is an absence of insulin absorption or absence of insulin altogether), in healthy patients you can measure both the rise in blood sugar and the rise in insulin in the bloodstream. A rise in insulin would show that erythritol indeed has enough carbohydrate to trigger that negative feedback loop in the body (insulin being released in the presence of sugar or carbohydrate to keep blood sugars at a normal level). This effect would not be able to be observed in diabetics since we do not have that insulin response, and the insulin has to be either injected under the skin or taken as a pill (depending on the type of diabetes you have). The result of the study was that erythritol did not increase blood sugar or insulin levels in the blood, and that about 85% of the erythritol was passed in the urine, showing that it truly has a net carbohydrate amount of basically zero (Noda et al., 1994).

MY MINI-EXPERIMENT
Based on all this evidence, it’s pretty clear that erythritol has no net carbohydrates, as well as no effect on blood sugar, and is a great sweetener alternative for those with diabetes. With this in mind, I felt safe conducting my own mini-experiment to satiate my curiosity once and for all. What happens when I drink a bottle of coconut water without giving myself insulin? I designed a procedure where I fasted for 1.5 hours, then checked my blood sugar for a benchmark value. I then drank a bottle of Core™ coconut water, waited 30 minutes, then rechecked my blood sugar to see if there was an effect. If there was a significant rise in my blood sugar, I would know that all the zero-carb claims about erythritol are false. But if my blood sugar stayed stable, I would know that all the evidence I had researched was true, and that erythritol is not absorbed by the body, and thus has no effect on blood sugar. So I did it! I fasted for 1.5 hours, and checked my blood sugar, and it was a perfect 90 mg/dL (this is the unit of measurement for blood sugar; it measures the mg of glucose per dL of blood). So I proceeded to chug a bottle of my favorite Core™ coconut water, and then I waited apprehensively for 30 minutes, wondering what my blood sugar would be, and hoping it hadn’t skyrocketed. Then the moment of truth came. After the 30 minutes were up, I checked my blood sugar, and it had risen only 7 mg/dL (making it 97 mg/dL), a negligible amount in the grand scheme of my blood sugar trends.

CONCLUSION
So that’s it then! Definitive proof that the body does not absorb erythritol, and therefore it has no effect on blood glucose levels! The tiny rise in my blood sugar that we saw (from 90 mg/dL to 97 mg/dL) was negligible and likely could have simply been from the natural fluctuation in blood sugar that is common throughout the day. This got me thinking about the times I had given insulin for my coconut water, and I remembered that after the injection and drinking the coconut water, my blood sugar had actually dropped! In addition, the studies from Ishikawa and Noda et al. show that erythritol has no effect on blood sugar for both diabetic and normal individuals. So, while you look at the label on the back of an erythritol-sweetened coconut water and see 9-18g of carbohydrates, rest assured that those are the total carbohydrates and not the net carbohydrates. The net carbohydrates are likely to be much lower, if not zero. This is important for diabetic to know especially, so that they do not give insulin for a carbohydrate that will not affect their blood sugar, avoiding hypoglycemia (a blood sugar level that is lower than is healthy).
The moral of the story? Coconut water with erythritol is a great post-exercise hydration choice for its vitamin and mineral content, but not if you want a carbohydrate-rich recovery drink. However, it is a great hydration choice for diabetics and people who need to monitor their blood sugar levels more closely! Not to mention it tastes great too!

Ishikawa, M, et al. (1996) Effects of Oral Administration of Erythritol on Patients with Diabetes. Regulatory Toxicology and Pharmacology, 24 (0112), S303-S308.

Miller, M. (2018, March 05). Everyone on the Keto Diet is Obsessed With This Sugar
Replacement. Women’s Health. https://www.womenshealthmag.com/food/a19055328/erythritol-side-effects/

Noda, K., Nakayama, K., Oku, T. (1994). Serum glucose and insulin levels and erythritol
balance after oral administration of erythritol in healthy subjects. European Journal of Clinical Nutrition, 48 (4), 286-292. https://europepmc.org/article/med/8039489