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Does Coffee impact Blood Sugar Level? - A personal experiment





I had a history of unmanaged diabetic condition with H A1C hovering between 8.2 and 10. In the recent months, I have successfully lowered my fasting blood sugar level by following a stricter diet and walking daily. My goal is to reverse the diabetic condition, and eliminate the medications.


Diabetic condition develops over a long period of time. Hence, anything that led to this condition should be acting slowly and subtly on our system over a long period. The hysteresis effect of our environment on our biomes is still a nascent study. The number of variables and the long deterioration period makes it a complex and expensive study for isolating the root causes. The absence of commercial incentives (i.e. blockbuster drugs) makes this kind of research hardly funded, thus prompting me to conduct this experiment.


I have been a heavy coffee drinker (4-5 cups a day). In the recent months, I had lowered my coffee consumption to about 2 cups a day. I witnessed significant lowering in my fasting blood glucose during the same period, though with stricter diet plan and increased activity. I wanted to verify whether coffee had been a contributing factor to my uncontrolled diabetic state, given the relationship between coffee and cortisol secretion.


Experiment Design


1) Measure fasting blood sugar level for 20 days continuing coffee drinking (2 cups a day)


2) Stop drinking coffee and all caffeine products, and measure fasting blood sugar level for the subsequent 20 days.


Each cup of coffee included fat free milk and Splenda. During the coffee drinking period, I had green-tea once in few days. No changes were made to the diet, activity and medications, except for the day-to-day variations in diet and activities across the entire period.


I chose a minimum of 20 days based on following assumptions:

1) 20 day period is sufficient for our bio-Hysteresis to reflect the effect of not drinking coffee

2) 20 day period cancels the daily variations in diet and walking, creating statistically significant data set


Experiment Result

(Pl check out the attached pdf for the graph)


Summary Data: With Coffee (No Coffee)

Min 91.00 (83.00)

Max 153.00 (130.00)

Range 62.00 (47.00)

Variance 248.66 (182.05)

Std. Deviation 15.77 (13.49)

Average 111.35 (103.45)



The test results showed a modest decrease in the average fasting blood sugar level of about 8 mg/dL, after I stopped drinking coffee. During the no-coffee period, I also witnessed lesser variations in the blood sugar levels.


The decrease in average blood sugar is not as significant, compared to the decrease that I experienced with stricter diet and walking. With the current results, it is not possible to isolate whether it was the caffeine, the low fat milk or the sweetener that led to the lower fasting glucose level. It is also possible that the bio-hysteresis takes a longer than 20 days to show the true impact of stopping coffee.


Based on this encourage result, I have decided to continue to stay away from coffee. I also invite the readers to validate this experiment by conducting their own test and share their findings.


Recommended Comments

wannabeat - thanks for posting this.  interesting experiment and conclusions.  i do believe, and I have read many articles that suggest that drinking coffee does impact bg, especially if carbs are on board.  i think the impact for T1s may be a little different than for T2s.  it seems that we are more sensitive to many impacts. ymmv

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It's been about two years since you started this blog, with the statement that your goal was to reverse the diabetes condition.  How are you progressing on that front?  Does anybody reach that goal?

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