Diastase is a mixture of enzymes that break down starch into smaller sugars. Discovered in 1833 by French scientist Anselme Payen, it holds the distinction of being the very first enzyme ever identified. The term “diastase” was later largely replaced by “amylase” in the early 20th century, but you’ll still encounter the older name in brewing, honey testing, and digestive supplement labels. Understanding what diastase actually does helps make sense of why it appears in so many different contexts.
How Diastase Works
Starch is a long chain of sugar molecules linked together. Your body can’t absorb it in that form, so it needs to be chopped into smaller pieces first. That’s exactly what diastase does: it breaks the bonds holding those chains together, releasing simple sugars like glucose and maltose that cells can use for energy.
Diastase isn’t a single enzyme. It’s a complex that includes several types of amylase, each targeting different parts of the starch molecule. Alpha-amylase cuts bonds in the middle of the chain, producing shorter fragments. Beta-amylase works from the ends, releasing two-sugar units called maltose. A third enzyme in the mix, limit dextrinase, handles branching points where the starch molecule splits into a Y shape. Together, these enzymes dismantle starch thoroughly and efficiently.
The complex works best under specific conditions. Its optimal pH is around 5.0, though it stays active across a range of 4.0 to 7.0. Temperature matters too: peak activity occurs at about 40°C (104°F), with a useful working range of 30 to 50°C. Go much hotter and the enzymes start to unfold and lose their shape permanently.
Diastase in the Human Body
Your body produces its own version of diastase in two places: the salivary glands and the pancreas. The salivary and pancreatic forms differ slightly in size and structure, but they do the same job.
Starch digestion starts the moment you chew. Salivary amylase mixes with food in your mouth and continues working as the food travels into the stomach and small intestine. This might seem surprising, since stomach acid is highly acidic, but during a meal the food itself acts as a buffer, keeping conditions closer to neutral and allowing the enzyme to keep functioning. Salivary amylase alone can account for up to 50% of all starch digestion. Pancreatic amylase, released into the small intestine, handles the rest.
Diastase in Brewing and Distilling
Brewers have relied on diastase for centuries, even before anyone knew what enzymes were. When barley is malted (soaked in water and allowed to germinate), the grain activates its natural diastase enzymes. During the next step, called mashing, the malt is mixed with hot water. The diastase complex attacks the gelatinized starch and converts it into a range of fermentable sugars: glucose, maltose, maltotriose, and others. Yeast then feeds on those sugars to produce alcohol.
The brewer’s ability to control temperature during mashing is really a way of controlling diastase. Lower mashing temperatures favor beta-amylase, which produces more fermentable sugars and a drier, thinner beer. Higher temperatures favor alpha-amylase, leaving behind more complex sugars that yeast can’t consume, resulting in a sweeter, fuller-bodied beer. The concept of “diastatic power,” measured in units called degrees Lintner, tells brewers how much starch-converting capability a given malt has. Higher diastatic power means more enzymatic punch.
Diastase in Honey
If you’ve ever seen a honey label mention “diastase number” or “DN,” that’s a quality marker. Bees add diastase to honey during production, and the enzyme gradually degrades with heat and age. Testing for diastase activity is one standard way to check whether honey has been overheated or improperly stored. A low diastase number suggests the honey has lost freshness or been processed at high temperatures, which also damages flavor and other beneficial compounds.
Diastase as a Digestive Supplement
Diastase appears as an ingredient in many over-the-counter digestive enzyme supplements, sometimes listed as “fungal diastase” because it’s derived from a mold source rather than animal tissue. These products are marketed to people who feel bloated or uncomfortable after starchy meals.
There is a well-established medical use for amylase supplementation, though it’s part of a broader enzyme replacement rather than diastase alone. People whose pancreas doesn’t produce enough digestive enzymes, a condition called exocrine pancreatic insufficiency, benefit from prescription enzyme supplements. This can happen with chronic pancreatitis, pancreatic cancer, cystic fibrosis, or certain forms of diabetes. These prescription formulations contain a standardized mix of enzymes that handle starches, proteins, and fats together.
For people with normal pancreatic function, the evidence behind standalone diastase supplements is far less robust. Your body already produces plenty of amylase in two separate organs, and healthy digestion doesn’t typically need a boost. That said, some people with functional digestive discomfort report subjective improvement with enzyme supplements, even if clinical data doesn’t strongly support the practice.
Diastase vs. Amylase: The Naming Confusion
The terms diastase and amylase overlap significantly, which causes confusion. Here’s the simplest way to think about it: diastase is the original 1833 name for the starch-digesting enzyme complex. The word “enzyme” itself didn’t even exist until 1877, when Wilhelm Kühne coined it. As biochemistry matured, scientists reclassified diastase under the more precise name “amylase” and further divided it into three categories: alpha-amylase (found in humans, animals, plants, and microbes), beta-amylase (mainly in plants and microbes), and gamma-amylase.
In modern scientific literature, “amylase” is the standard term. But “diastase” persists in brewing, honey grading, and supplement marketing because those industries adopted the word long before the rename happened. When you see either term, the underlying biology is the same: enzymes that convert starch into sugar.