When coffee drinkers over-indulge in sweets, many notice an immediate craving for coffee. The combination of coffee and dessert is common and traditional in many regions, as is the taking of bitter herbs (often in an alcoholic beverage) as a digestive aid. The desire to consume coffee together with sweet flavors could be due to coffee’s bitterness, but there may also be some beneficial effect on blood sugar levels that elicits a craving for coffee when blood sugar levels surge.

Some dieticians and researchers consider coffee detrimental to blood sugar levels because it (or the caffeine in it) stimulates the adrenal glands. This stimulation increases the production of hormones (adrenaline and glucagon) that cause the release of stored sugars into the blood. It is one of the ways a stimulant prepares the body for increased physical activity and higher energy demands.

There follows a supposition that sweetened coffee aggravates this effect by putting sugar into the blood, both via the digestive system and by releasing stored sugars through hormonal stimuli. When there is insufficient physical activity to consume the extra energy from the sugar, the pancreas responds by pumping out insulin. Insulin decreases sugar levels in the blood by driving it into the cells of the body – putting it back into storage. Physiologically, it’s like taking an “upper” and a “downer” at the same time, in a convoluted attempt to stay on an even keel.

There are concerns that the increased demand for insulin can lead to decreased sensitivity to it – as happens with Type 2 diabetes and metabolic syndrome. And there has been research indicating that caffeine (taken as an isolated drug) inhibits sugar metabolism.

However, a several studies in 2006 and 2004 indicate that coffee consumption is actually associated with a decreased incidence of Type 2 diabetes. Although any study has its weaknesses, these were conducted in different geographic areas, with different participants and different methodologies, and did their best to account for confounding factors such as obesity and smoking.