The landmark study demonstrating astaxanthin's benefits for Sjogren's syndrome (SS)-related dry eye and dry mouth—with implications for systemic sicca symptoms like vaginal dryness—is the 2010 clinical trial by Yamada et al., published in Journal of Clinical Biochemistry and Nutrition.

In this investigation, 12 mg/day oral astaxanthin for 2 weeks in 6 SS patients with xerostomia reduced oxidative stress (HEL adduct: -10%, p=0.03) and trended toward increased salivary flow (1.02 to 1.04 g/2 min), while significantly boosting saliva in normals (6.23 to 7.02 g/2 min, p=0.03).

Supported by mouse models showing preventive effects on irradiation-induced hyposalivation, it positions astaxanthin as an ROS scavenger to alleviate SS glandular dysfunction, where dry eye/dry mouth affect >90% of patients.

Title: Evaluation of Therapeutic Effects of Astaxanthin on Impairments in Salivary Secretion

The landmark study on phytoceramides' (glucosylceramide) benefits for xerostomia—with implications for Sjogren's-related dry eye and vaginal dryness—is the 2019 double-blind randomized cross-over trial by Murakami et al., published in Nutrients.
In this RCT, 1.2 mg/day oral pineapple-derived glucosylceramide for 2 weeks in 16 patients with subjective xerostomia significantly increased lingual mucosal moisture (31.70% to 32.35%, p=0.03) and improved dryness VAS scores (p<0.05) vs. placebo, without altering papillae count. As a plant sphingolipid boosting barrier hydration, it targets sicca symptoms across ocular, oral, and vaginal mucosa.

Title: Impact of Oral Intake of Glucosylceramide Extracted from Pineapple on Xerostomia: A Double-Blind Randomized Cross-Over Trial

The landmark study on anthocyanidins 25–35% from Aristotelia chilensis (MaquiBright®) for dry eye—with implications for Sjogren's-related dry mouth and vaginal dryness—is the 2018 randomized, double-blind, placebo-controlled trial by Yamashita et al., published in Clinical Ophthalmology.
In this RCT (n=74 with eye dryness/fatigue), 60 mg/day MaquiBright® (~21 mg anthocyanins) for 4 weeks significantly increased tear production (Schirmer test: +6.4 ± 8.1 mm both eyes, p=0.005; left eye p=0.001) and reduced symptoms (DEQS bothersome score p=0.037; VAS eye fatigue p=0.047) vs. placebo, via antioxidant modulation of lacrimal glands.

Title: Effects of MaquiBright® on improving eye dryness and fatigue in humans: A randomized, double-blind, placebo-controlled trial

The landmark study on c polyphenols from Camellia sinensis (green tea extract) for dry eye and xerostomia—with implications for Sjogren's-related vaginal dryness—is the 2014 phase II double-blind, placebo-controlled, randomized clinical trial by De Rossi et al., published in Oral Diseases.
In this RCT (n=60 patients with xerostomia, including Sjögren syndrome cases), a natural lozenge formulation containing green tea catechins (standardized to high polyphenol/catechin content, equivalent to ~200–400 mg total catechins daily over 8 weeks) significantly increased unstimulated saliva output (3.8-fold, p<0.05) and stimulated saliva (2.1-fold, p<0.05) within 1 week vs. placebo, while improving quality-of-life scores for oral dryness. By targeting oxidative stress in salivary glands via EGCG-mediated antioxidant modulation, it extends to ocular and mucosal hydration benefits in sicca syndromes.

Title: A Phase II Clinical Trial of a Natural Formulation Containing Tea Catechins for Xerostomia