Coffee: Which Type is the Healthiest?


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May 13, 2016
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The Choice Between Light, Dark, or Medium​

Coffee has several superpowers, but they’re determined by how long the beans are roasted. Here’s how to choose the right one for your needs.

It wouldn’t be a revelation to say that coffee is a popular beverage for athletes and non-athletes alike. Humans have been consuming it at least since 1,000 AD. In the USA, it’s the number one source of caffeine consumption 6 (1,2).

For those who don’t consume much in the way of fruits and vegetables, it’s also an important source of phytonutrients and has various potential health benefits, according to epidemiological studies (3,4).

The question remains, though: Does one roast (light, medium, or dark) have more healthful attributes than the others? Well, let’s find out.

The Roasting Process​

When roasting coffee beans, the raw beans are subjected to heat for a specific amount of time, typically resulting in a change of color from the raw, green bean to a yellow and subsequent light brown color, which further darkens as the bean roasts. The higher the temperature and time of roasting, the darker the roast.

Light Roast​

Light roast coffee is subjected to the least amount of heat. This result? More chlorogenic acids are retained in the finished coffee. These chlorogenic acids are responsible for some of the potential health benefits of coffee, including potential weight loss (5).

Dark Roast​

Dark roast coffee is subjected to the greatest amount of heat, which, unfortunately, results in the degradation and transformation of the chlorogenic acids. However, while dark roast coffee is much lower in chlorogenic acids, it’s rich in N-methylpyridinium, a degradation product of the trigonelline formed during roasting. While not touted as often as the chlorogenic acids, N-methylpyridinium-rich dark roast coffee also has some potential health benefits:

  • A dark roast coffee blend reduced DNA damage in healthy men and women consuming 500 mL per day (about 4 cups) over 4 weeks (6). An 8-week study also found similar results in those consuming 750 mL/day (7).
  • In pre-obese people consuming 500 mL of coffee a day for 4 weeks (8), a dark roast coffee increased weight loss while a light roast didn’t. (Normal-weight subjects consuming dark or light roast had no significant change.)
  • Another study indicated potentially increased thermogenesis via uncoupling protein-2 (UCP-2) expression, which was increased in healthy, normal-weight men and women consuming 750 mL/day of dark-roast coffee over 4 weeks (10).
  • There’s also evidence that dark roast caused reduced calorie intake, body weight, and body fat, along with a slight gain in fat-free mass in healthy men and women consuming 750 mL/day over 4 weeks (11). The decrease in body fat was greater to a statistically significant extent than a medium roast (11). A 24-week study also found a decrease in fat mass in those consuming 4 cups per day of a medium dark roast (20).
  • Dark roast increased the antioxidative status of red blood cells to a greater extent than light roast coffee (8).
  • Dark roast increased glucose metabolism to a greater degree than light roast in healthy men consuming 4 cups/day for 1 week (12).
  • Dark roast inhibited phosphodiesterase or PDE in vitro to a greater degree than light roast at identical concentrations (13). PDE is the enzyme that breaks down cAMP – a second messenger involved in various processes, including lipolysis.
  • In vitro data demonstrated potentially greater anti-inflammatory effects with dark roast coffee versus lighter roasts (14). There’s also evidence suggesting that dark roast may be easier on your stomach than light roast (15).
  • In humans, dark roast coffee demonstrated a greater increase in the transcription factor (Nrf2) which is responsible for inducing the expression of antioxidant and cytoprotective/detoxifying enzymes that activate our own body’s naturally evolved defense mechanisms against chronic oxidative stress and xenobiotic harm (16-18). Activation of Nrf2 is at least partially responsible for the benefits of foods such as broccoli (19). However, some studies have found only a minimal influence of dark roast coffee on Nrf2 (7).

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Let’s Go to the Scorecard​

While these points may make it seem as though dark roast is the obvious choice, there are some limitations to note:

  • While in vitro data found dark roast inhibited PDE to a greater extent than light roast, a human study that administered a dark and medium roast found little difference in PDE activity. Whether a light roast coffee would’ve been different is unknown, but there were substantial differences in the content of chlorogenic acids and N-methylpyridinium (10). (Caffeine itself can’t effectively inhibit PDE in humans at normal concentrations, so this is an interesting finding.)
  • With the exception of a greater decrease in body fat, the decreases in body weight, calorie intake, and a slight increase in fat-free mass weren’t statistically different between a dark and medium roast (11). Both dark and medium roast demonstrated a decrease in body fat and a slight increase in fat-free mass (11). Additionally, increases in UCP-2 weren’t statistically different between a medium and dark roast, and the increase in the dark roast may have been confounded by time effects (10).
  • While in vitro data demonstrated potentially greater antioxidative and anti-inflammatory effects with dark roast, other data generally show greater antioxidative and anti-inflammatory effects with light roast (21). In an animal model, the results were mixed (22).
  • While dark roast increased UCP-2 expression in humans, a medium roast was able to increase the hormones adiponectin and leptin, while dark roast wasn’t. These hormones play a role in energy homeostasis and may have anti-obesity effects. It should be noted, only the effect upon leptin was statistically significant for medium versus dark roast (10).
  • While one study found dark roast coffee increased glucose metabolism, another found that dark and light roasts are no different in terms of an effect on glucose or insulin levels (23).
  • A study in overweight men and women consuming around 4-5 cups/day for 3 months experienced no difference in weight loss when comparing dark and medium roasts (24).
  • Another study found effectively similar antioxidative effects in people consuming medium and dark roast coffee (25).
  • Chlorogenic acid, a major constituent of light roast but not dark, has some evidence for causing a decrease in fat mass in overweight individuals (26).

A Comparison of Caffeine Levels​

There are studies showing that both dark and light roasts may have more caffeine than the other, but more importantly, these differences aren’t substantial enough to base your choice on the potential amount of caffeine present (14,27-30). In other words, it’s a toss-up.


How About Acrylamide Levels?​

Acrylamide and its presence in coffee made the news media rounds a few years ago because acrylamide is classified as a “probable” human carcinogen by the International Agency for Research on Cancer (IARC).

Acrylamide can be formed via the Maillard reaction, which requires the presence of an amino acid, a reducing sugar (e.g., glucose or fructose), and heat. This is the main mechanism through which it occurs, not only in coffee but many other foods, especially potatoes and baked goods (31,32).

Frying, baking, grilling, roasting, toasting, and microwaving carbohydrate-rich foods can generate acrylamide formation (31,32). Boiling or steaming is okay.

While vegetables and meat can form some acrylamide when subjected to these cooking methods, it’s generally much less than baked goods and potatoes (31-33). For coffee and other plant-based sources of acrylamide, the amino acid asparagine is considered the main contributor to acrylamide formation (34).

Despite rather significant consumption of acrylamide, epidemiological studies have largely failed to find any evidence of an increased risk of cancer from consumption of acrylamide from dietary sources (35-38). While risk assessments based largely upon animal model data have indicated concern for acrylamide consumption, intake from coffee alone probably isn’t something to be concerned about (38-42).

Consumption of acrylamide in coffee isn’t done in a vacuum and should certainly be considered distinct from the consumption of foods such as baked goods, fried potato chips, and other potato products, as well as tobacco smoking, which are significant sources (43).

Coffee, however, has antioxidant and anti-inflammatory 4 effects which may mitigate the potentially harmful effects of acrylamide and its metabolite. Besides, the Maillard reaction that’s responsible for producing acrylamide in coffee is also responsible for producing at least some of the antioxidative and anti-inflammatory effects of coffee while also producing many of the smells and tastes of coffee that people covet (34,44,45).

Epidemiological studies have either failed to show an association between coffee consumption and cancer or have shown a reduced likelihood (46-51).

The bottom line? Coffee alone isn’t something to be too worried about with respect to acrylamide consumption. In fact, the IARC more recently concluded that coffee itself shouldn’t be considered “possibly carcinogenic” and that increased cancer risk from drinking coffee is specifically related to esophageal cancer and consumption of very hot liquids – tea, coffee, or even water. So, consider drinking your beverages, including coffee, at a reasonable temperature – below 150 degrees Fahrenheit – for risk reduction.

Nonetheless, if you want to reduce the amount of acrylamide in your coffee, opting for medium and dark roasts is best. The acrylamide is degraded/transformed as the roasting temperature and time rise, causing a substantial decrease in the amount of acrylamide present in medium and dark roasts relative to light roasts (52-54).

So, What’s the Best Coffee to Drink?​

There isn’t enough evidence to suggest that you should only drink one roast versus another. As with most things in life, variety is ideal. If you normally drink only light roast, give medium or dark a try for a few weeks and vice versa. Ultimately, drink the coffee you enjoy the most.