The evidence from peer-reviewed sources like Nature Communications Biology and Frontiers in Cellular and Infection Microbiology confirms the core scientific assertions in the claim.
1. Protective Status: L. crispatus is widely recognized as the most beneficial species because it produces high levels of lactic acid, which maintains an acidic environment hostile to pathogens. It is linked to reduced risks of Bacterial Vaginosis (BV), STIs, and preterm birth.
2. Prevalence and Dominance: Sources indicate that while many women have some Lactobacillus, L. crispatus dominance (CST-I) is not universal. One study noted it was present as the dominant microbe in "well under 40% of women," while another study of Kenyan adolescents found it in roughly 40% of the group, noting this was "substantially higher" than in adult populations. The 25-30% figure cited in the claim aligns with broader global averages for reproductive-age women.
3. Genetic and Environmental Factors: The evidence supports the idea that this microbiome state is influenced by a mix of genetics (heritability estimated at ~35%), hygiene, and sexual activity.
4. The '100/100' Score: It is important to note that the "100/100 score" mentioned in the original post is likely a proprietary metric from a specific commercial testing lab rather than a standardized medical classification, though the underlying data (98.7% dominance) represents an exceptionally high concentration of the bacteria.
Source quality: The evidence includes multiple peer-reviewed studies from reputable journals (Nature, PubMed, Frontiers) that specifically address L. crispatus prevalence, its protective mechanisms, and its heritability.
