Cacti belong to the Cactaceae family and are succulents, meaning they have specialized tissues designed for maximum water storage. While it is true that cacti hold a significant volume of liquid within their fleshy bodies, the belief that this fluid is safe and refreshing drinking water is largely a dangerous myth. In reality, the complex chemical composition of the internal pulp in most species makes it unsuitable for human consumption and can even hasten dehydration in a survival situation.
How Cacti Store Liquid in Arid Environments
Cacti have developed specific adaptations to thrive in environments where water is scarce. The most noticeable adaptation is the replacement of typical leaves with spines, which drastically reduces the surface area from which water can be lost through transpiration. This mechanism minimizes water vapor escaping into the hot, dry air, preserving the plant’s internal moisture.
The main body of the cactus, the stem, is covered in a thick, waxy cuticle that acts as a waterproof barrier. The stem itself is structured like an accordion, with ribs that allow the plant to expand significantly after a rare rainfall event, storing water. Internally, the stem tissue consists largely of water-storing parenchyma cells, which hold a mucilaginous, spongy pulp. This pulp is not pure water but a thick, slimy substance that helps the plant retain moisture for extended periods, functioning like a living reservoir to sustain the cactus during long droughts.
The Chemical Danger of Cactus Liquid
This fluid often contains high concentrations of acids and defensive chemicals known as alkaloids, which the plant produces to deter thirsty animals. The presence of these compounds is what makes the liquid from many species, such as the Barrel Cactus, extremely unpalatable and potentially toxic.
A significant danger comes from the high concentration of mineral salts and organic acids, including oxalic acid, within the pulp. Ingesting this highly acidic and mineral-rich fluid creates a high osmotic load in the human digestive system. The body attempts to dilute these concentrated substances, which requires drawing water from the bloodstream and tissues, paradoxically accelerating dehydration rather than relieving it.
Consuming the acidic cactus pulp can also induce severe gastrointestinal distress, including vomiting and diarrhea. In a survival scenario where a person is already dehydrated, this physiological reaction is counterproductive and can quickly lead to a worse, potentially life-threatening condition.
Separating Myth from Reality: Identifying Usable Species
While the internal fluid of most cacti is hazardous, a few species offer edible parts, but these should be viewed as food sources rather than emergency hydration. The Prickly Pear cactus (Opuntia species) is the most notable exception, with both its pads, called nopales, and its fruit, known as tuna, being widely consumed. The pads and fruit contain significant moisture and are rich in vitamins, antioxidants, and minerals, making them a source of both nutrition and hydration when properly prepared.
The fruit of the Prickly Pear, in particular, contains a sweet, watery pulp that is sold commercially as “cactus water” and is known to be hydrating and rich in betalain antioxidants. However, consuming the core pulp of the main cactus stem remains generally ill-advised. Some species of Barrel Cactus, specifically the Fishhook Barrel Cactus (Ferocactus wislizeni), have been historically cited as a source of moisture, but even their pulp is often too acidic and unpleasant to be effective for emergency hydration.
The crucial distinction is that the edible, hydrating parts are the fruit or the pads, not the thick, mucilaginous pulp from the main body of the plant. Even with the few exceptions, relying on a cactus for water in a life-or-death situation is highly risky due to the difficulty in identification and the chemical composition of the plant’s core. The best survival strategy is always to carry ample water and prioritize reliable sources rather than attempting to extract moisture from the body of a cactus.