The nopal cactus grows across the Americas. People eat its pads and fruit, and also take them as powders, juices, or liquid extracts. The soluble fiber in nopal slows sugar absorption when you have it with meals. For that reason, folks often take it right before they eat.
This same fiber supports regular digestion. Prickly pear also supplies antioxidants that help protect cells from oxidative stress. Some reach for it after drinking to ease next-day grogginess.
Be careful: prickly pear can drop blood sugar and may not mix well with diabetes medications. It has a mild diuretic effect and may shift blood pressure.