Pardon the potentially silly inquiry, but I couldn’t stop wondering about this. Also, please excuse any awkward phrasing, as English is not my native tongue.
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It appears that oral sex can indeed affect health, but potentially in a negative way. Some research has indicated that men who engage in oral sex with more partners may face a higher risk of developing mouth and throat cancers.
Short response: no.
Check my other comment for a full explanation.
Summary: The lactobacillus species and strains found in the vagina are distinct from those in the gut (in healthy women).
Giving oral sex is not a source of free probiotics.
Additionally, please refrain from trying to produce “vaginal yogurt.” (I’m serious…).
Source: I am a professional researcher focused on the human microbiome.
Update: Here are several papers on the topic, as many have asked. I previously shared these in a comment that was deleted. Some were published just weeks ago, though the findings have been discussed in the field for a while.
Selective maternal seeding and environment shape the human gut microbiome - PMC PubMed
Update 2: These references specifically address the sub-topic of whether infants maintain their mother’s vaginal flora after birth, rather than the direct question about oral sex and digestion.
I believe you would need to ingest over 500 million CFUs for the bacteria to successfully colonize your gut flora. I’m not sure if a typical session would involve that much.
Cicerone here: lactobacillus is actually the essential bacteria used in many sour, German-style wheat beers. If you’re interested for health reasons, it might be more pleasant to just drink a gose or a berlinerweisse now and then. Ps: this post made me chuckle.
I have experience working in a lab where we isolated natural compounds from lactobacillus found in vaginal swabs. Most lactobacillus species are facultative anaerobes that create biofilms, which helps them live in low-pH environments like the gut, mouth, and vagina. While no study has looked at the exact scenario you’re asking about, there are lactobacillus strains used in probiotics today that aim to seed the gut via fermented food and drink. It isn’t scientifically sound to claim oral sex directly changes your digestive microflora, but it is documented that lactobacillus can produce molecules that fight off external microbes and support a healthy microbiome, and they are capable of surviving in the environments involved in oral sex.
Sources:
[1]https://www.cell.com/cell/fulltext/S0092-8674(14)01102-7
[2]Structure, function and diversity of the healthy human microbiome | Nature
[3]PubMed
A brief search turned up some articles you might already be familiar with. There are various studies on female sex workers regarding their lactobacillus levels and species in relation to STDs. One paper in particular noted that higher levels of lactobacillus in the vagina were linked to a decreased risk of HIV infection. https://academic.oup.com/jid/article-abstract/180/6/1863/868231
Did knowing this lead you to wonder if oral sex might provide similar benefits?