 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. So researchers stuck pH probes down in the 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. We 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 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 in acceleration of stomach acid secretion returning the stomach to acidic conditions three times faster than drinking dark roast coffee. Hence the title, 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 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 pure roast 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 pure roast low acid coffee will become almost immediately obvious to those who suffer from acid reflux, heartburn, or indigestion, with over 90% 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, I mean 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 some orange juice company going out of the way to destroy the vitamin C, and then branding their OJ as low acid. And that would be technically true, like 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, I mean if it causes less stomach discomfort, maybe it's worth it. 30 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 pure roast brand low acid coffee, versus conventionally roasted regular Starbucks coffee. And to the funder 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 9% of customers' claim. No significant differences in the frequency or severity of heartburn, regurgitation, or dyspepsia were demonstrated. Between the two coffees, either in a fasting state or after a 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.