Coca-Cola as Birth Control: Myth or Fact?

In 2008 gynaecologist Deborah Anderson decided to study¹ whether post-sex Coca-Cola douches were a legit method of preventing pregnancy.

Back in the 50s and 60s, the acidity of Coke was rumoured to be a good sperm killer, but additionally, the classic shape of the glass Coca-Cola bottle was ideal for the ‘shake and shoot’ method of application.

Thus, in a 1987 study², each variety of Coke (and Pepsi) was tested for its spermicidal qualities.

Before we go any further, basically, it doesn’t work. But you’re curious, right, so here’s why Coke isn’t good contraception – and which fizzy drink is!

Why are people even doing this in the first place?

Women have been washing sperm out of their vaginas to try to avoid pregnancy for time immemorial. With few options prior to our current comparative glut of birth control, women did what they could.

Going into the 1900s, there were a few more options around, including antiseptic douches. The marketing for these douches, such as Lysol, was coded in classic white person 1950s prudishness: the ads said to douche for musty vaginas and saving relationships, but everyone knew that you used them for killing sperm and bacteria.

Douches were widely used as contraception, however, this was later proved to be a useless method. These douches built on the idea that you could wash sperm away and not get pregnant, with some liquids superior to others.

Coke became a popular post-coital douche, but then birth control as we know it came along. Coke was left for oral refreshment.

Except, the soda-kills-sperm idea hasn’t died completely everywhere, especially in those areas in which modern contraception isn’t easily available. When money is tight and education is low, you know what’s always around? Coke.

And are they wrong? Or just wrong to use Coke?

A 1992 study² in Nigeria looked into the spermicidal qualities of a local fizzy bitter lemon drink, Krest. Krest worked much better than Coke as a spermicide, immobilising sperm inside a minute.

Coke, on the other hand, doesn’t work well as contraception for two reasons, Anderson’s paper explains: first, Coke is not a very strong spermicide, but second, sperm are faster (and smaller) than the Coke.

Yes, sperm are faster than Coke

A 2006 study³ found that human sperm can swim at over 18cm per hour. That might seem kinda slow, but a sperm, when deposited right up next to the cervix, doesn’t have far to go to get to safety. Sperm can swim through the cervical canal in seconds, taking it immediately out of reach of the Coca-Cola fizz.

If you consider how long after the sex it would take you to take a breath, get the Coke, shake it and shoot it, you’re looking at 30 seconds minimum.

Coke damages vaginal cells

Anderson’s research team tested Coca-Cola on vaginal epithelial cells (the top layer of cells) and found that brief exposure visibly damaged the cells and reduced transepithelial electrical resistance (TEER).

TEER is a measure of how permeable the tissue barrier is, which could change how susceptible a vagina is to ‘accepting’ an incoming pathogen, such as a virus. That is, catching a sexually transmitted infection.

Coke used vaginally, therefore, may increase risks of vaginal infection in a very specific way.

Other reasons why Coke is a bad idea for birth control

The high sugar content may increase yeast and bacterial overgrowth
Carbonated drinks may negatively impact healthy flora
The force of the ‘shake and shoot’ method may push pathogenic bacteria into the cervix, promoting pelvic inflammatory disease
Nobody knows exactly what’s in Coke – the recipe is a secret
Execution of the douche requires skill and flexibility
The bottles are glass, which may present a danger if broken or pushed too far into the vagina
We have better contraception options (but if you must use fizzy drink, try the bitter lemon…)

References

1.
Anderson DJ. Coca-Cola douches and contraception. BMJ. December 2008:a2873-a2873. doi:10.1136/bmj.a2873
2.
Nwoha PU. The immobilization of all spermatozoa in vitro by bitter lemon drink and the effect of alkaline pH. Contraception. December 1992:537-542. doi:10.1016/0010-7824(92)90118-d
3.
Cooper TG, Yeung C-H. Computer-aided evaluation of assessment of “grade a” spermatozoa by experienced technicians. Fertility and Sterility. January 2006:220-224. doi:10.1016/j.fertnstert.2005.07.1286