Friday Favorites: Which Coffee Is Healthier— Light Roast, Dark Roast, or Low Acid?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Intro: Light roast, dark roast, low-acid? Are there different health benefits to these different kinds of coffee? Watch the video to find out.

For those drinking non-paper-filtered coffee, like boiled, French press, or Turkish coffee, the amount of cholesterol-raising compounds in the lightest roast coffee may be twice as high compared to using very dark roast beans. So, it appears some of the cholesterol-raising compounds are destroyed by roasting. So, in this case darker would be better, or, you can just use a paper filter and eliminate 95 percent of the cholesterol-raising activity of coffee, regardless of the roast, as I’ve described before.

But I did another video showing dark roasting may also destroy up to nearly 90 percent of the chlorogenic acids, which are the antioxidant anti-inflammatory phytonutrients purported to account for many of coffee’s benefits. So, in that case, light roast would be better. On the other hand, dark roasting can wipe out up to 99.8 percent of pesticides in conventionally-grown coffee, and more than 90 percent of a fungal contaminant called ochratoxin, which is a potent kidney toxin found in a wide range of food ingredients that can get moldy.

But then, what about the polycyclic aromatic hydrocarbon products of combustion that are “suspected to be carcinogenic” and DNA-damaging? Darker roasts may have up to four times more than light roasts. Thus, they advocate controlling roasting conditions to cut down on these combustion compounds. Just to put things in perspective, even the darkest roast coffee might only max out at a fraction of a nanogram of benzopyrene per cup—considered to be “the most toxic” of these compounds—whereas a single medium portion of grilled chicken could have over 1,000 times more.

Overall, you don’t know if light versus dark roast is better until you… put it to the test. This study found that “Dark roast coffee is more effective than light roast coffee in reducing body weight…” Folks were randomized to a month of drinking two cups a day of light roast coffee or dark roast coffee, roasted from the same batch of green coffee beans. And in normal weight subjects, it didn’t seem to matter—no significant weight changes either month—but in overweight study subjects, they ended up about six pounds lighter drinking dark roast coffee compared to light roast coffee; more than a pound a week lost just drinking a different type of coffee.

What about light versus dark in relation to blood sugars? We’ve known since 2015 that even a single cup of coffee can affect the blood sugar response. Here’s the blood sugar spike over two hours after drinking a cup of coffee with more than a dozen sugar cubes in it (like a quarter cup of sugar in one cup of coffee), compared to the spike from the same amount of sugar in just plain water. What is not known is whether this increase in blood sugars is actually clinically meaningful. After all, coffee consumption does not seem to increase the risk of diabetes, and if you compare light roast coffee to dark roast coffee right before chugging down about 20 teaspoons of sugar, there didn’t appear to be any difference. Perhaps the take-home message is: light or dark, maybe we shouldn’t be adding 20 spoonfuls of sugar.

And finally, what about the effect of different roasts on heartburn and stomach upset? We’ll find out next.

“Dark roast coffee is more effective than light roast coffee in reducing body weight…” But what about the effect of different roasts on heartburn and stomach upset?

We know that “Coffee consumption is sometimes associated with symptoms of stomach discomfort.” And so, researchers stuck pH probes down into people’s stomachs to measure the amount of stomach acid generated by different types of coffee. The way you chart stomach acid secretion in the stomach is called a “gastrogram.” You basically give people some baking soda, which starts out alkaline, and measure the pH in the stomach to see how long it takes the body to restore the stomach back down into an acid bath: about 15, 20 minutes. But if you mix that same amount of baking soda with dark roast coffee, it takes longer, meaning the dark roast coffee is suppressing stomach acid secretion, since it takes longer to normalize the pH.

Give people more of a medium roast coffee, though, and we see a dramatically different effect— an acceleration of stomach acid secretion, returning the stomach to acidic conditions three times faster than drinking dark roast coffee. Hence the title: “A dark…roast coffee… is less effective at stimulating [stomach] acid secretion…compared to a medium roast [coffee].” But, you don’t know if that translates into symptoms—clinical effects—until you put it to the test.

“The most commonly used coffee bean roasting process is referred to as convection or ‘flash’ roasting,” which just takes a few minutes. “An alternative method is conduction roasting,” which roasts at a lower temperature for a longer time—hours—and this results in so-called low-acid coffee. And, supposedly, there are anecdotes from coffee-sensitive individuals suggesting that this low-acid coffee “does not precipitate or aggravate heartburn.” When you look up that citation, though, they just cite data from the Puroast Coffee company, makers of low-acid coffee. It should therefore come to no surprise that it was the same company that funded the study.

If you go to their website, they claim that “The health benefits associated with drinking Puroast Low Acid coffee will become almost immediately obvious to those who suffer from acid reflux, heartburn, or indigestion,” with over 90 percent of customers surveyed receiving symptom relief. And so, they decided to put their money where their mouth was. But before I get to the results, it’s important to realize that when they say low-acid, they’re not talking about stomach acid; they’re talking about roasting so long that they destroy more of the chlorogenic acid within the coffee bean. You know the antioxidant, polyphenol, phytonutrient chlorogenic acid? You know the “anti-diabetic, anti-[cancer], anti-inflammatory, anti-obesity” antioxidant?

That’s like an orange juice company going out of their way to destroy the vitamin C, and then branding their OJ as “low-acid.” And, that would be technically true—vitamin C is ascorbic acid—but they’d be bragging about destroying some of the nutrition, and that’s exactly what low-acid coffee makers are doing. But hey, if it causes less stomach discomfort, maybe it’s worth it?

“Thirty coffee-sensitive individuals completed [a] randomized, double-blind, crossover study in which the symptoms of heartburn, regurgitation and [stomach upset] were assessed following [the] consumption [of the Puroast brand low-acid coffee versus conventionally roasted regular Starbucks coffee].” And, to the funder’s chagrin, no benefit whatsoever was found with the low-acid coffee. “Consumption of both coffees resulted in heartburn, regurgitation, and [stomach upset] in most individuals.” So much for that ridiculous 90 percent-of-customers claim. “No significant differences in the frequency or severity of heartburn, regurgitation, or dyspepsia were demonstrated between the two coffees, either in the fasting state or after the test meal.” They couldn’t find any way to make the low-acid coffee look better.

So, they had this initial thought that a difference in coffee acidity may explain the company’s claims. However, when put to the test in a randomized, controlled study, they found “no difference” in symptoms, suggesting the whole coffee acidity thing doesn’t explain the sensitivity some people have. And, I think, further acts as a reminder that we should never believe claims made by anyone trying to sell us something.

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Image credit: Free-Photos via pixabay. Image has been modified.

Image credit: Vladimir Proskurovskiy via unsplash. Image has been modified.

Motion graphics by Avocado Video