Is light roast coffee healthier and less bitter than medium roast? When it comes to at least two categories of nutrition, mild or lighter roasted beans are actually not as good for you. But don't worry, there's good news for those who prefer their mild taste.
The Good: Antioxidant Content
Choosing your flavor based on this wouldn't make sense. Why? Because the ORAC values for light, medium, and dark are quite similar:
ORAC value of light roast = 2,450
ORAC value of medium roast = 2,780
ORAC value of dark roast = 2,690
With many foods this pattern is not the case, but it turns out much of the antioxidant activity in the coffee bean isn't significantly affected by the heat endured during the roasting process.
The Bad: Acrylamide Content
If you aren't familiar with acrylamide, it's a Group 2A carcinogen according to the World Health Organization. Aside from industrial applications, it is also found in almost every cooked food we eat. The heat changes the food on the molecular level, creating this molecule. In particular, it's found in fried, baked, and roasted carbohydrates. Of course, beans - including coffee beans - are a carb and for that reason, a relatively high amount of acrylamide is created during the process of roasting them.
The good news is that very little - almost none on a relative basis - is found in properly filtered coffee. If you were to eat the coffee grinds, that is when you would be consuming a lot. For that reason, snacks and desserts containing chocolate covered roasted coffee/espresso beans are a terrible idea, at least if you want to do what's best for your health.
Which coffee has the the most acrylamide? Unfortunately it tends to be the lighter roasts. This may seem counter intuitive since they are cooked less and therefore, one would conclude they should have less. The reason that's not the case is because the acrylamide forms during the early phases of the roasting process. Fully roasted beans contain less, because the acrylamide has formed and then broken down by the time that stage is reached.
That being said, light coffee is not unhealthy for you. Since light, medium, and dark roasts - in their brewed and filtered form - all have acrylamide in parts per billion, hardly any is present. Just make sure you filter your coffee carefully and adequately. Stay away from French presses for that reason.
The Bad: Light Is More Acidic
This is something else which may seem counter intuitive. On average, lighter roasted coffee beans are more acidic than medium and darker roasts. The unpleasant, astringent quality decreases the more the beans are roasted, because it breaks down the acid. What is the least bitter coffee? A dark bold, such as an Italian or French roast. Though bitterness aside, not everyone likes the more robust flavor, which brings us to the last point on our list.
The Good: Low Acid Options
Many people, whether due to health issues or simply a preference, do not drink coffee because of the bitterness and acidity. As a result, quite a few roasters and brands have begun producing lower acid beans using specialized roasting processes and selected crops which have naturally less. You can buy low acid coffee brands in light, medium, and dark roasts.
Research Support, Non-U.S. Gov't: Carlsen MH, Halvorsen BL, Holte K, et al. Nutrition Journal NIH Jan 2010