Kidney stones are hard deposits made of minerals and salts that form inside the kidneys, often causing severe pain as they pass through the urinary tract. Edibles are ingestible forms of cannabis, such as gummies, brownies, or beverages, which deliver their active compounds through the digestive system. This article investigates the current scientific understanding of the relationship between consuming cannabis edibles and the development of these renal deposits, known medically as urolithiasis. The central question is whether the unique metabolism of edibles or their non-cannabis ingredients contribute to the formation of kidney stones.
Current Research on Cannabis and Kidney Stone Risk
Epidemiological data currently do not establish a direct causal link between cannabis consumption and the formation of kidney stones. Cannabis use has not been identified as a standard risk factor like diet, hydration, or genetics. Large-scale population studies analyzing the association between marijuana use and a history of kidney stones offer mixed, but generally reassuring, findings.
One study analyzing data from the National Health and Nutrition Examination Survey (NHANES) found that regular marijuana use was inversely associated with kidney stones in males, suggesting a lower risk compared to non-users. This inverse relationship was observed in males who reported using marijuana one to six times per week. Researchers speculate this potential reduced risk could relate to the anti-inflammatory or mild diuretic effects of some cannabinoids.
These studies typically examine general cannabis use, which includes both inhaled and edible forms, and rely on self-reported data. However, the overall body of evidence suggests that the primary compounds in cannabis, such as Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), do not directly promote the crystallization process in the kidneys.
How Edibles Are Metabolized and Affect Renal Function
The process by which an edible is broken down is significantly different from inhaling cannabis, influencing the compounds that eventually interact with the kidneys. When consumed, the primary psychoactive compound, Delta-9 THC, undergoes first-pass metabolism in the liver, carried out by enzymes in the cytochrome P450 complex.
The liver converts Delta-9 THC into a highly potent psychoactive metabolite called 11-hydroxy-THC (11-OH-THC). This is further oxidized into 11-nor-9-carboxy-THC (THCCOOH), the primary inactive metabolite. Both 11-OH-THC and THCCOOH are then prepared for excretion, primarily through conjugation with glucuronic acid to increase their water solubility.
The majority of THC metabolites are excreted through the feces, but about 20% leave the body via the urine. THCCOOH-glucuronide is the most abundant metabolite found in the urine, and its highly water-soluble nature makes it unlikely to contribute to the formation of hard, insoluble crystals. There is no evidence suggesting these specific THC metabolites alter urinary pH or mineral concentration in a way that promotes the crystallization of calcium oxalate or uric acid, the most common stone types.
Non-THC Factors Influencing Kidney Stone Formation
While the cannabis component itself appears low-risk, non-cannabis factors associated with edible consumption may indirectly influence kidney stone risk. The most significant factor in stone formation is chronic dehydration, which leads to concentrated urine where minerals can easily precipitate. Cannabis effects, such as dry mouth or altered awareness, could inadvertently lead to reduced fluid intake, increasing the concentration of stone-forming substances.
The ingredients used to create the edible product are another potential source of risk. Many commercially produced edibles are high in added sugars, including high-fructose corn syrup. High sugar intake can increase the risk of kidney stones by affecting calcium and oxalate excretion, and has been linked to increased urinary calcium levels, a key factor in calcium stone formation.
Specific ingredients may also contain high levels of oxalate, a compound that binds with calcium to form the most common type of kidney stone. Ingredients like chocolate, nuts (e.g., almonds, cashews), and certain spices, often found in cannabis-infused treats, are naturally high in oxalates. This risk is related to the food vehicle, not the cannabinoid, and primarily concerns individuals susceptible to calcium oxalate stones.