Malt is made from grains, and since grains aren’t Paleo, neither is malt.
What It Is
Malt is made by germinating grains (usually barley) by soaking them in water, then drying them with hot air. This modifies the starches in the grains into sugars, including glucose, maltose, maltotriose, and maltodextrines.
Essentially, it does the work for us of breaking down the sugars to make them more digestible. This is actually bad, because grains are already off the Paleo menu largely due to their high carbohydrate content. By modifying the starches before we eat them, the malted grains cause an even higher spike in blood sugar. This sugar rush can leave many people feeling light-headed and just generally “off”.
Mark Sisson has a more comprehensive list of the ways we pay the price when consuming sugar.