I have been tracking my own blood glucose for several years to better understand the impact of things like diet, fasting, exercise, sleep, travel and I’ve previously written and spoken about the importance of tracking, managing, and optimizing one’s blood glucose even if, like me, you are not diabetic. If left unchecked, glucose can damage cells via multiple mechanisms and can play a key role in many medical conditions including obesity, type 2 diabetes, hypertension, cardiovascular disease, and liver disease [1]. This post focuses on tracking glucose response from different foods to optimize diet.

Why Managing Glucose Response After Meals is Important

Limiting postprandial glycemic response is an important factor in reducing the risk of chronic metabolic diseases, and contributes to significant health benefits in people with elevated levels of blood sugar.

Organizations such as the American Diabetes Association (ADA) suggest a general goal is for a blood sugar level under 180 mg/dL 1 to 2 hours after beginning a meal [3]. However, many experts suggest maintaining much lower levels because has been shown that chronically elevated post-prandial blood sugar levels (staying above 140 mg/dL for a significant period of time) can have severe consequences like irreversible beta cell loss [4] (cells that produce insulin) and nerve damage [5]. 

Postprandial glucose response curve

Typically after eating a meal, blood glucose will temporarily rise as the body breaks down digestible carbohydrates into sugar, which enters the blood [2]. The body, in turn, produces insulin which signals cells to pull in this blood sugar for energy or storage. Known as post-prandial blood sugar measurements, this type of rise, peak, and fall is common.

Inspiration – Personal Glycemic Response Study

A few years ago a very interesting paper was published in the journal Cell titled “Personalized Nutrition by Prediction of Glycemic Response,” where 800 participants consumed various carbohydrate-rich foods while having their blood sugar levels monitored. Researchers found that different people responded very differently to identical meals – for example, chart E below on the left compares the glycemic responses of two individuals (participant #468 at the top and participant #663 at the bottom) after consuming a pure glucose drink versus white bread:

Postprandial glycemic response foods study

While participant #468 had what could be considered a more typical response (pure glucose drink raising blood sugar much higher than white bread), participant #663 had a much higher spike in blood glucose from eating white bread than pure glucose!

The study also looked at individualized glycemic response after consuming equal amounts of carbohydrates (50g) from different foods (also known as “effective” or “net” carbohydrates where fiber is subtracted from total carbs). For example, chart G above on the right shows two other participants’ (#445 and #644) individual glycemic responses to both bananas and cookies. While participant #445 had a good glucose response to cookies but not bananas, participant #644 had an opposite response!

Tracking My Personal Glycemic Response to Different Foods

Inspired by this study, I began to look at my own personal glycemic responses to different foods. Using my Precision Xtra fingerstick glucose meter, I would measure my blood sugar just prior to eating a food item, then at 15- to 30- minute intervals for the next 3 hours. I would also make sure not to have consumed anything other than water for a few hours prior.

Personal Post-Prandial Glycemic Response to White Rice, Bananas, Apples, and Pea Protein

Measuring personal postprandial glucose response to foods

Not surprisingly, eating white rice not only spikes my blood glucose, but sustains those elevated levels for a long period of time. Bananas also spike my blood glucose, but rise is more delayed and results in a shorter spike before coming back down. Apples are a bit more complex to digest so there is a longer delay before my glucose levels rise. And for comparison, something like pea protein that has few carbs has very little effect on my glucose levels.

Optimizing Post-Prandial Glucose by Combining Foods

While understanding one’s personal glycemic response to, say, white rice is insightful the reality is that we typically don’t eat foods in isolation – white rice would be consumed along with a larger meal. So, we should also be looking the combined effects of different foods so we can use that data to our advantage.

Taking manual fingerstick blood sugar readings every 15 minutes with every meal can prove impractical over time (eating out at restaurants, etc.) so I was able to procure a FreeStyle Libre continuous glucose monitor that would continuously sample my blood sugar 24 hours a day for a period of 2 weeks.

Awesome Meal tracking app

I also started recording everything I ate and drank. Turns out I co-developed a simple photo-based meal tracking app called Awesome Meal Tracking (free on iOS and Android), that allowed me to keep a timestamped record of everything I ate or drank just by taking photos. I could then match the timestamp of each food item with data from my glucose sensor to create post-prandial glucose response charts.

I found that by adding just a tablespoon of of olive oil (fats) to the same serving of white rice, my glucose levels would rise less and come down faster:

Personal postprandial glycemic response white rice

Here is my glycemic response after eating a homemade, “keto-friendly” meal of grass-fed ground beef, sautéed rainbow chard, sweet potato, and half an avocado:

Personal postprandial glycemic response to keto meal

Similarly, drinking a cup of “Bulletproof” coffee (organic coffee, grass-fed butter, MCT oil) has little impact on my blood sugar levels:

Personal postprandial glycemic response to Bulletproof coffee

Conversely, check out how going out to a Thai restaurant and eat a plate of Chicken Pad Thai wreaks havoc on my blood glucose:

Personal postprandial glycemic response to Chicken Pad Thai

Surprisingly, certain types of alcohol (such as hard cider) will actually lower my blood sugar:

Personal postprandial glycemic response to hard cider

Summary

By better understanding our personal glycemic responses to different foods, we can eliminate (or at least, minimize) those items that cause large, sustained spikes in blood sugar. We can also identify ways to combine foods to help buffer elevated glucose levels after meals!

The Future of Personalized Nutrition

Several companies, like Viome, Onegevity Health, and DayTwo (started by researchers from the original glycemic response paper) have been analyzing large sets of personal glucose data and combining that information with individual gut microbiome sequencing to develop models that can accurately predict glycemic responses of different foods for any individual, and in turn provide personalized dietary guidance, regardless of whether someone is paleo, keto, vegetarian, or vegan!

Resources

Fingerstick Glucose Meters:

Precision Xtra Glucose and Ketone Meter (Amazon)

Keto-Mojo Glucose and Ketone Meter

Continuous Glucose Monitors:

FreeStyle Libre Continuous Glucose Monitoring System (website)

Dexcom G6 Continuous Glucose Monitoring (CGM) System (website)

Reading:

Wired To Eat, by Robb Wolf (Amazon)

Microbiome Testing / Dietary Recommendation Services:

Viome (website – save over 50%!)

Onegevity Health Gutbio (website)

DayTwo (website)

About Bob

Bob Troia is a technology entrepreneur and citizen scientist who is focused on the intersection of data-driven citizen science, health and wellness, human performance, longevity, and self-optimization. He has been featured on CBS News Sunday Morning, PBS NewsHour Weekend, National Geographic Explorer, CBC (Canada), SBS-TV (South Korea), Fast Company, Men's Fitness, Outside Magazine, and on many leading health and wellness podcasts.

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