Research shows that drinking coffee regularly reduces insulin and blood sugar levels while caffeine does the opposite. The likely implication is that coffee can protect against acne whereas other caffeinated drinks could be bad for your skin.
In this post I’m going to explain what the science says about the effect of coffee and caffeine on acne, and what this means to you.
Brief on insulin-acne connection
Let’s start with a brief recap on how insulin and high blood sugar level contributes to acne. When blood sugar level increases the pancreas responds by releasing the hormone insulin. Insulin in turn stimulates the release of other acne-causing hormones, such as insulin like growth factor 1 (IGF-1) and androgens. These hormones increase sebum production and skin cell growth, leading to blocked pores and acne. For more detailed explanation, please see the hormonal acne post.
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The implication is that anything that has a persistent negative effect on insulin level (i.e. causes insulin resistance/increases insulin level) can be bad for your skin. This is the reason sugar and milk cause acne.
Coffee has well-documented effects on both blood sugar and insulin levels, and these are the most likely mechanisms by which it affects acne. So let’s see what the science says about the effect on coffee on blood sugar health.
The effect of regular coffee consumption on blood sugar health
One of the most impressive studies I found was a Dutch study on older people. The study included 1312 over 50 years old Dutch people. The researchers administered an oral glucose tolerance test (OGTT) at the start of the study and another one 6 to 7 years later. OGTT measures how well your body handles sugar and involves drinking a cup of water with 75 grams of sugar (for reference 20 oz/590 ml bottle of Coke has 65g of sugar) and having blood sugar and insulin levels measured 2 hours later. Caffeine consumption was tracked with a food frequency questionnaire.
The study showed that regular coffee consumption was very good for blood sugar health. This image shows the incidence of impaired glucose tolerance (IGT) vs. coffee consumption.
The blue bars indicate the percentage of people who developed impaired glucose tolerance (IGT) during the study. IGT is diagnosed when your blood sugar level remains abnormally high at the 2 hour mark of the OGTT. It means your body had trouble clearing sugar from bloodstream and indicates insulin resistance.
The red line shows risk ratio between groups, with the 2 or fewer cups per day being the reference point. Those who drank 7 or more cups per day had risk ratio of 0.44, so they were 56% less likely to develop IGT than those who drank 2 or fewer cups per day. Makes sense?
The paper also contained an interesting table that showed the change in blood sugar health parameters when daily coffee consumption goes up by 5 cups. Note that negative values mean improvement, as negative values refers to lower, and thus better, values.
|Insulin resistance (HOMA-IR)||-6.3%|
The ‘2-hour’ values refer to measurements in OGTT and thus represent what happens after a meal. Those are fairly significant improvements, especially the nearly 20% lower insulin level.
This is by no means an isolated result, 19 out of 22 such studies show similar results. So there’s overwhelming evidence to show that drinking coffee regularly lowers blood sugar and insulin levels, and thus is indirectly good for acne.
Caffeinated beverages may have the opposite effect
Though drinking coffee is good for blood sugar and insulin levels, caffeine alone may have the opposite effect. There has long been a paradox in coffee research. Epidemiological studies (like the Dutch study above) show protective effect from coffee, but short-term studies where participants are given caffeine almost uniformly show caffeine causes insulin resistance and higher blood sugar level.
The implication is that caffeine in coffee impairs glucose tolerance but over time something else in coffee offsets this negative effect. It could be the antioxidants in coffee or something else, scientist haven’t figured it out yet.
From this you could conclude that decaffeinated coffee is the best choice. It, presumably, still has the beneficial substances in coffee but has minimal amounts of caffeine. A 2006 study showed this indeed is the case.
In this study 11 participants got regular coffee (RCOF), decaffeinated coffee (DECAF), a caffeine pill (CAF), or a placebo pill (PL) on 4 separate occasions. 60 minutes later OGTT was administered. Here are the results:
Note that in those graphs the time ‘0 min’ refers to when caffeine/coffee/etc. was ingested, and time ’60 min’ when the sugar drink was given.
As you can see, ingestion of decaffeinated coffee resulted in the lowest blood sugar and insulin levels and ingestion of pure caffeine resulted in the highest levels, with regular coffee being in the middle. And we are not talking about small differences here. The researchers calculated ‘area under curve’ figures (a good estimate of total amount of insulin or glucose in the blood during 2 hours) for all the cases. Compared to RCOF, DECAF resulted in about 50% less glucose in the blood during the 2 hours, and a whopping 69% reduction when compared to CAF. In the case of insulin, DECAF resulted in 23% lower insulin load than RCOF and 38% lower when compared to CAF.
This was a very small study (only 11 participants), but I’m using it as an example for two reasons: bigger studies on caffeine have shown similar results, and it’s one of the few studies that compared regular coffee, decaffeinated coffee, pure caffeine and placebo.
The conclusion from this line of research is that consuming caffeine before a meal results in higher blood sugar and insulin levels following the meal. The implications are:
- Consuming caffeinated beverages can have a bad effect on blood sugar levels, especially if those beverages also have sugar (i.e. Coke and some other soft drinks).
- You shouldn’t eat anything sweet with your coffee as the caffeine in coffee will interfere with insulin and result in higher blood sugar and insulin levels.
- Drinking decaffeinated coffee can reduce post-meal blood sugar and insulin levels. It’s possible that green tea had the same effect.
I would conclude that drinking coffee regularly is probably good for your skin, but you should drink it black without added sugar or coffee, and it’s a good idea not to have anything sweet with your coffee (so keep your hands out of the cookie jar). Switching to decaffeinated coffee could be even better for your skin. You should avoid other caffeinated beverages (such as sodas and energy drinks) as they have caffeine but lack the protective substances found in coffee and tea.
In the grand scheme of things, coffee is probably only a minor factor in acne. Other factors, such as diet, gut issues and stress are likely to have much larger effect than coffee or caffeine.
- Coffee consumption and incidence of impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes: the Hoorn Study. (Full text PDF)
- Caffeine Impairs Glucose Metabolism in Type 2 Diabetes.
- The Glucose Intolerance Induced by Caffeinated Coffee Ingestion Is Less Pronounced than That Due to Alkaloid Caffeine in Men.
- Decaffeinated Coffee and Glucose Metabolism in Young Men.
- Caffeine ingestion impairs insulin sensitivity in a dose-dependent manner in both men and women.
- Glucose homeostasis remains altered by acute caffeine ingestion following 2 weeks of daily caffeine consumption in previously non-caffeine-consuming males.
- Caffeinated coffee consumption impairs blood glucose homeostasis in response to high and low glycemic index meals in healthy men.
- Caffeine ingestion elevates plasma insulin response in humans during an oral glucose tolerance test.
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