Key takeaways:
- For some people, consuming carbohydrates along with caffeine increases blood glucose levels — a lot.
- For others, the combination doesn’t cause a dramatic increase.
- Genetic variants in the adenosine receptor combine with variants in the caffeine metabolism gene to create unique blood glucose responses.
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Caffeine, adenosine, alertness, and blood glucose
Adenosine builds up in the brain all day as you use ATP for energy. As more and more adenosine builds up and binds to the adenosine receptor (ADORA2A), it causes you to get drowsy. This is one reason we feel sleepy and are driven towards sleeping each night.
Caffeine binds to the adenosine receptor, ADORA2A. It isn’t the same as adenosine, though, so instead, it blocks the action of adenosine at the receptor. This is why caffeine makes you feel more alert — due to the lack of adenosine binding to the receptor. (More alert until the caffeine wears off and you suddenly feel really sleepy due to the adenosine that is still hanging around and now able to bind to the receptors.)
Adenosine also inhibits norepinephrine and epinephrine release, so when caffeine blocks the receptor, it allows for norepinephrine and epinephrine to be released (surge of energy). Epinephrine, though, also upregulates glucose mobilization… and thus a link to glucose response to caffeine.
The CYP1A2 enzyme breaks down the caffeine in the body, and those with the genetic variants break it down at different speeds. This is why some people can’t drink caffeine after lunch without it affecting their sleep — and others can drink a cup of coffee at dinner and still sleep well that night.
Blood glucose response:
Previous studies showed an increase in glucose response when people consumed caffeine prior to a meal — when averaging the response across a large group. However, coffee consumption is associated with a decrease in the risk of type-2 diabetes, overall.[ref]
It turns out that the question of whether caffeine increases glucose response in an individual is based on their genes and whether it is consumed with carbohydrates.
Caffeine and carbohydrates: Interactions with 2 genes
A study in Nature investigated how the genetic variants for caffeine metabolism interact with carbohydrate consumption.[ref]
The experiment detailed in Nature used a cross-over design where 18 male participants (in their mid-20s) visited a lab two different times to test their response to caffeine and carbs.
The participants consumed carbohydrates (a sports drink with sugar) initially to see what their glucose response was to carbs. Next, the researchers measured their blood glucose response to carbohydrates plus caffeine (sports drinks with sugar plus caffeine added).
The participants were genotyped for their ADORA2A and CYP1A2 variants.
The results showed that those with the CC genotype of the ADORA2A variant (listed below) had more of a postprandial glucose response with caffeine compared to the baseline without caffeine. For the participants with the CT and TT genotypes of ADORA2A, there was no difference in glucose response with caffeine vs. without.
The CYP1A2 variant increased the length of time of the response.
This study is unique in that it tests individual responses based on genotype compared with the individual’s own baseline.
Sugar and Caffeine Genotype Report
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Lifehacks:
Generally, it’s healthier not to have a big spike in your blood glucose levels after you eat or drink a beverage.
Testing this out:
Checking your blood glucose levels with an inexpensive glucose monitor is a great way to see how caffeine increases your levels. You can get a finger-stick type test kit at Walmart or any drug store. Another alternative is to talk with your doctor about getting a continuous blood glucose monitor.
Coffee without sugar – or – Coffee without caffeine:
If you normally drink coffee with sugar first thing in the morning, you may be elevating your glucose levels more than just from the spoonful of sugar. Consider drinking your coffee black or just with cream. Alternatively, if you don’t have a way around combining carbs with your coffee, you could try decaf or half-caff coffee to see if that makes a difference.
Alternatives to coffee in the morning include mushroom-based hot drink mixes, hot herbal teas, or chicory.
Soft drinks:
Consider switching to a drink without caffeine in it if you are consuming it with sugar or carbs. For example, unsweetened tea is an alternative.
Decrease carbohydrates when you consume caffeine:
If you don’t want to give up caffeinated drinks, you could decrease your carbohydrate intake. For example, if you normally consume caffeine in the morning (coffee, black tea), then go with a low-carb breakfast choice such as eggs and sausage or cottage cheese.
Recap of your genes:
| Gene | RS ID | Your Genotype | Notes for Your Genotype | Effect allele | Effect allele frequency |
|---|---|---|---|---|---|
| ADORA2A | rs5751876 | — | typical; caffeine increases postprandial glucose responsecaffeine does not affect postprandial glucose responsecaffeine does not affect postprandial glucose response | T | 0.42 |
| CYP1A2 | rs762551 | — | typical; caffeine does not affect glucose responselonger glucose elevation when caffeine is added to carbslonger glucose elevation when caffeine is added to carbs | C | 0.31 |
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