The role of vitamin A in the vagina and urinary tract

Vitamin A is anti-inflammatory and involved in restoring healthy epithelial cells to damaged mucosal surfaces.

Vitamin A promotes and regulates the innate immune system and adaptive immunity, thus enhancing immune function against infections. These include urinary tract and vulvovaginal infections.

Vitamin A is what’s known as a micronutrient critical in the human body for vision, growth and development, and protecting the epithelium and mucosal surfaces. Our digestive tract, urinary tract, reproductive tract and respiratory tract are all mucosal surfaces.

Vitamin A is a fat-soluble vitamin that comes in three forms: retinol, retinal and retinoic acid.

How vitamin A supports the vagina and urinary tract

Epithelial cells line the outer and most inner surfaces of the body and are the first line of defence against invading pathogens. Vitamin A plays an important role in the epithelium, from the formation, keratinisation, stratification, differentiation and maturation of epithelial cells. That is, every part of the life cycle of a skin cell.

Vitamin A promotes mucin secretion. Mucin is essentially mucous laden with special protective proteins. Mucins have a protective effect on the underlying tissue.

The mucin found most often in the mouth and vagina is MUC5B. This mucin significantly reduces attachment of pathogens such as streptococci, Candida albicans, Helicobacter pylori and HIV, while also reducing pathogens’ ability to form biofilms on epithelial cells. MUC5B doesn’t kill bacteria but keeps the bacteria in its free-floating (planktonic) form, adding to the diversity of flora and keeping things ‘normal’.

Vitamin A promotes mucin secretion and improves the antigen non-specific immune function of the underlying tissue.

In the urinary tract, we know that vitamin A maintains the structure, form, and number of lining epithelial cells. That is, it keeps urinary tract cells looking good and in sufficient numbers to protect underlying tissue.

When epithelial cells are deprived of vitamin A, they are replaced by stratified squamous keratinising epithelium – hard dead cells.

Without vitamin A, epithelial cells shrink and keratinisation can occur, leading to symptoms. Keratinisation means cells fill with keratin protein filaments and die, forming a tough structure – think dry, tough skin on the heels, and nails.

The change of cells to keratinised epithelial cells reduces resistance to pathogens, as the healthy epithelial barrier is no longer intact. This change in cell type means innate immunity of the underlying tissue is decreased and infections are promoted.

Immune organs require constant replenishing of vitamin A. Retinoic acid plays a critical role in regulating the differentiation, maturation and function of innate immune system cells, such as macrophages and neutrophils – the immediate responders to pathogenic invasion.

Macrophages and neutrophils conquer invaders via phagocytosis (ingestion of invader) and the activation of natural killer T cells.

References

Huang Z, Liu Y, Qi G, Brand D, Zheng SG. Role of Vitamin A in the Immune System. J Clin Med. 2018;7(9):258. Published 2018 Sep 6. doi:10.3390/jcm7090258

Kahbazi M, Sharafkhah M, Yousefichaijan P, et al. Vitamin A supplementation is effective for improving the clinical symptoms of urinary tract infections and reducing renal scarring in girls with acute pyelonephritis: a randomized, double-blind placebo-controlled, clinical trial study. Complement Ther Med. 2019;42:429‐437. doi:10.1016/j.ctim.2018.12.007