Are the health benefits of dark roast coffee the same, better, or worse than the lighter varieties? To answer this question, you need to know these two vital pieces of information (1) the amount of antioxidants in each, and (2) the amount of acrylamide in each.
While not of interest to most people, knowing the caffeine content is also important for those with certain health conditions such as heart disease, high blood pressure, hormonal imbalances, hypoglycemia/blood sugar issues, acid reflux, and frequent urination. However this laundry list is highly controversial and there is strong research supporting the opposite, that moderate coffee consumption may actually benefit many of these health conditions. This is too big of a can of worms to get into here, so let's just focus on the nutrition facts for you to draw your own conclusion.
Does dark roast coffee have more caffeine than light? Many people are under the impression that the amount of caffeine in the bean actually increases when it is roasted. That is a myth but if you have thought that don't feel bad, because many culinary "experts" have perpetuated this myth to the public (which is likely why so many of us believe it).
It actually turns out that the opposite is true.
Caffeine is a highly stable compound and therefore, it's not very affected by the intense heat during the bean roasting process. The average temperature at which the beans are roasted is around 500 degrees Fahrenheit. It would take an additional 100 degrees (600+) before caffeine amounts would noticeably be affected, according to Scribblers Coffee Company (a popular Ohio-based roaster).
However even at 500 degrees, some degradation still occurs. For that reason, light coffee does have more caffeine than dark, not less. But before you dump your dark French or Italian roast in favor of a light blonde, the difference is so negligible it's not worth choosing one over another for that reason; only a low single digit percentage reduction in the caffeine content occurs, if that.
When foods are heated, especially above 300 degrees, Advanced Glycation End products (AGEs) form. These are suspected carcinogens. With carbohydrate-rich foods, the type of AGEs which form are primarily acrylamide. This may sound scary but the good news is that the total levels of AGEs formed in cooked plants is far less than cooked animal sources (i.e. meats, fish, dairy, eggs). There are numerous techniques you can use to reduce acrylamide in food.
It is true that roasted coffee beans have an extremely high concentration of acrylamide. However a properly filtered coffee is a low source of acrylamide content relative to the vast majority of foods you eat daily.
For example, Starbucks ground Columbian coffee beans (not brewed) test out at 163 ppb (parts per billion). However that same brewed and filtered coffee produces only 7 ppb, which is over a 95% reduction in acrylamide. The reason for this is because the acrylamide is present in the roasted bean and the actual coffee, assuming its well filtered, contains little to no ground bean sediment. This is a reason we at Superfoodly prefer drinking paper filtered drip coffee, which removes substantially more sediment than the French press technique.
To put that 7 ppb in perspect, it is almost nothing. You should be more concerned about the Cheerios you're having at breakfast (266 ppb) with your cup of Joe, or your Trader Joe's Veggie Chips potato snacks (1,970 ppb) (1).
ORAC Values Compared
The best, most conclusive way to measure the antioxidant activity of a substance is with Oxygen Radical Absorbance Capacity (ORAC) testing. This is a patented process which was developed in the 00's by USDA researchers at Tufts University in Boston. Previously - as recently as 2012 - the USDA would publish the test results for many common foods but stopped doing so since the biological effects of antioxidants (in vivo) could not be conclusively proven. Being that they've only "proven" vitamin A and vitamin C in vivo and it took decades to accomplish, this is hardly a reason to ignore the thousands of other antioxidant types. According to the free radical theory of aging, oxidative stress is a major contributor to cell damage and mutations. For that reason it should not be ignored while we wait for 100% undeniable proof. Remember how many decades it took for the government to accept the proof that cigarettes had harmful side effects on our health?
The following values were reported in 2010 by CIRAD, which is an educational and research division of the French government. No brand names were specified and therefore, it should be concluded that these values represent the average for each degree of roasting.
ORAC value of regular/medium roast = 2,780
ORAC value of bold/dark roast = 2,690
ORAC value of light roast = 2,450
As you see there is a difference in the amount of antioxidants in regular vs. dark. vs. light, but they are all extremely comparable. The highest - regular roast - is only 13% above the lowest, the lighter bean. For this reason choosing your roast solely based on antioxidant content rather than preferred taste would not make much sense (it would be simpler to just drink 13% more, right?). Your better bet would be to buy a higher antioxidant coffee, some of which are shown below. It can be accomplished by using certain varieties of beans and proprietary roasting techniques to preserve the amount of natural antioxidants within them.
Research Support, Non-U.S. Gov't: Carlsen MH, Halvorsen BL, Holte K, et al. Nutrition Journal NIH Jan 2010