The use of Mexican Sarsaparilla (Smilax spp.) to support the adrenal cortex is primarily based on traditional herbal medicine practices rather than robust scientific evidence. Historically, sarsaparilla has been used in Central and South American folk medicine for a variety of ailments, including as a general tonic and for treating skin diseases, rheumatism, and as a "blood purifier." In herbal traditions, the root is sometimes included in formulas aimed at supporting energy and vitality, which are sometimes interpreted as connected to adrenal function due to the adrenal glands’ role in stress response.

However, direct evidence supporting sarsaparilla’s specific effects on the adrenal cortex or adrenal hormone production is extremely limited. There are no high-quality human clinical studies demonstrating that sarsaparilla has a measurable or clinically relevant effect on adrenal health. Most scientific research on sarsaparilla has focused on its potential anti-inflammatory, immune-modulating, and antioxidant properties, and its content of saponins and plant sterols. These general activities are often cited by herbalists as potentially beneficial for stress adaptation, but such claims remain speculative in the absence of targeted studies.

In conclusion, while sarsaparilla is traditionally used in some systems of herbal medicine for broad health support and sometimes included in "adrenal support" blends, there is little direct scientific evidence to validate its use specifically for the adrenal cortex.