Which herbal supplement is thought to aid in benign prostatic hyperplasia (BPH)?

Saw palmetto is widely recognized as an herbal supplement that may help alleviate symptoms associated with benign prostatic hyperplasia (BPH). BPH is a common condition in older men where the prostate gland enlarges and can cause difficulties in urination. Saw palmetto is believed to work by inhibiting the activity of certain hormones that contribute to prostate enlargement, potentially improving urinary flow and decreasing nighttime urination.

In contrast, other herbal supplements listed have different primary uses; for instance, St. John's Wort is primarily used for mood disorders, Ginkgo Biloba is often considered for memory enhancement and cognitive function, and turmeric is known for its anti-inflammatory properties. While these supplements may have various health benefits, they do not have the same targeted effect on BPH as saw palmetto does. Hence, the association of saw palmetto with BPH symptoms makes it the correct answer in this context.