Light vs. Dark Roast Coffee: What’s the Difference?

Before they’re roasted, coffee beans are green fruit seeds of Coffea plants, with little resemblance in color or flavor to the morning beverage we all know and love.

Roasting these green coffee beans evokes a variety of chemical, physical, and sensory changes in the beans and is ultimately what gives coffee its quintessential color, aroma, and flavor (1).

Coffee beans are usually roasted in large rotating drums, in which they’re heated for 5–15 minutes before being cooled and packaged.

It sounds like a simple process, but even slight changes in the time and temperature at which the beans are roasted can result in differences in the final product.

Light roasts are typically roasted between 350°F–400°F (177°C–204°C) for around 10 minutes or less (2).

Dark roasts are heated for closer to 15 minutes above 400°F (204°C). Medium roasts fall in between (2).

In short, the lighter the roast, the lower the temperature the beans are roasted at — and the shorter the time they spend in the roaster.

Heating coffee beans removes moisture, so dark roast beans tend to be light and puffy, while light roasts are dense and moist. Roasting also brings natural oils to the surface of the beans, which is why dark roasts tend to have a shine.

Summary

Dark roast coffee beans are heated to a higher temperature for a longer length of time than light roast coffee beans. These variations in roasting account for differences in the color, density, and moisture content of the beans.

Many of us reach for a cup of coffee first thing in the morning or when we need quick boost of energy. That’s because the caffeine in coffee stimulates brain activity and releases neurotransmitters that make you feel more alert and awake.

Therefore, you may wonder whether light and dark roast differ in terms of their caffeine contents.

There are misconceptions about which roast is higher in caffeine. Some people assume that the darker the bean, the higher the caffeine content. Others have heard that roasting burns off caffeine, meaning light roasts are actually higher in the stimulant.

However, dark roasts tend to be slightly lower in caffeine after the roasting process.

That said, recent and older studies alike suggest that the difference is negligible. As long as coffee is measured out by weight rather than by volume, the caffeine content between the two roasts is very similar (3, 4, 5, 6).

Because dark roast beans puff up with air and expand as they’re heated, measuring coffee by weight tends to be more accurate than measuring by volume, such as in teaspoons or tablespoons.

For example, one study found that a sample of light roast brewed coffee contained about 60 mg of caffeine, while the same amount of dark roast contained 51 mg of caffeine — though this discrepancy could easily vary between batches of beans (2).

On average, 1 cup (237 mL) of coffee contains about 100 mg of caffeine. The type of roast, the type of beans, and even the way that it’s brewed could all change that amount, though likely not by much (7, 8, 9).

Summary

Studies have found that dark roast coffee beans tend to contain slightly less caffeine than light roast coffee beans. However, that’s mostly due to the volume of the beans. When the two roasts are compared by weight, the difference is negligible.

After caffeine, the other reason why people are drawn to either light or dark coffee roasts is usually the flavor.

Compared with dark roasts, light roasts tend to have more delicate but complex flavor profiles. Because some of the initial flavors of the beans are lost or altered during the roasting process, dark roasts tend to have deep but simple flavors (10).

Light roast coffee also tends to have a thinner mouthfeel than dark roast. The natural oils present in dark roast coffee beans increase the viscosity of the final product, which makes it feel thicker in your mouth.

Light roast coffee is often described as:

• bright
• crisp
• acidic
• fruity
• floral
• herbal

Dark roast coffee is often described as:

• bold
• robust
• smokey
• chocolatey
• toasty
• nutty

Some people describe dark roast as more bitter than light roast, though the bitterness of coffee can be caused by many other factors as well — from the brewing time and the coffee-to-water ratio to the temperature of the water used and the grind size of the beans (11).

What’s more, where coffee beans are grown, the species of Coffea plant they came from, and the bean processing techniques can all influence the flavor of a cup of coffee (12).

For the best flavor, light roasts are often recommended for pour-over and drip coffee, while dark roasts are well suited for espresso drinks or those that use milk and cream.

You can try using different roasts when making different coffee drinks to discover new favorites.

Summary

Light roast coffee has a complex flavor profile that can be characterized as bright and acidic. Dark roast coffee has a simpler flavor profile, but it’s usually described as bold and robust.

Research has linked moderate coffee consumption — about 3 cups (about 710 mL) per day or less — to protection against Alzheimer’s disease, as well as associated it with reduced inflammation and better outcomes for those with type 2 diabetes (13, 14, 15, 16).

Still, many of these studies were based on observational results, which sometimes produce conflicting results. Therefore, more randomized controlled trials in humans are needed to determine coffee’s health benefits (17, 18, 19, 20).

Remember that many of the health benefits of coffee are contingent upon how much cream and sugar are added to the drink.

Nevertheless, it’s widely accepted that coffee contains bioactive nutrients, such as chlorogenic acid polyphenols, which may help with weight loss (21, 22, 23).

Older studies suggest that coffee also contains melanoidins, which may have a range of benefits, including reduced inflammation and antioxidant properties (24).

Though both light and dark roast coffees contain antioxidants and polyphenols, light roasts might be higher in these nutrients, as dark roasts lose somewhat more plant chemicals during the roasting process (2, 8, 25, 26).

On the other hand, a few studies have found dark roast coffees to be lower in acrylamide — a chemical that sometimes forms in foods that have been heated to high temperatures. Acrylamide has been linked to an increased risk of cancer (3, 25, 27, 28).

Summary

Light and dark roast coffees each have nutritional pros and cons. Light roasts may be higher in healthy antioxidants and polyphenols, but they might also contain higher amounts of a harmful chemical called acrylamide.

The differences between light and dark roast coffee result from the length of time the beans spent roasting and the temperatures they reached.

Light roast coffee beans are heated to a lower temperature for a shorter length of time than dark roast beans.

While there are some slight differences between the two, both types of beans contain plenty of caffeine, healthy nutrients, and delectable flavors.

Whether you should drink light or dark roast coffee is a matter of personal preference.