The immobilization of all spermatozoa in vitro by bitter lemon drink and the effect of alkaline pH

Contraception. 1992 Dec;46(6):537-42. doi: 10.1016/0010-7824(92)90118-d.


This study investigated the effects of increase in temperature and in pH of Coca-Cola, Afri-Cola, Pepsi-Cola and Krest bitter lemon drinks ("soft drinks") produced in Nigeria on the in vitro motility of spermatozoa. Semen was collected from 7 men, average age 28 years, of proven fertility, after 5 days' abstinence from sexual intercourse. The temperature and pH of the drinks were adjusted from 22 degrees C (room) to 37 degrees C, and pH 2.4 (acid) to 7.5 (alkaline), respectively. The mean % motility of spermatozoa in the adjusted and in the unadjusted drinks was compared for significant differences at the 1% level using the student's t-test. The results showed no significant differences in mean % motility in the drinks at 22 degrees C and at 37 degrees C. The mean % motility in all the drinks, except Coca-Cola, was significantly greater at alkaline than at acid pH; for Coca-Cola, motility was significantly greater at acid than alkaline pH. Of the drinks, Krest bitter lemon (unadjusted) immobilized all spermatozoa within 1 minute of addition.

Conclusion: i) alkalinity decreases the spermicidal action of all drinks except Coca-Cola, and ii) Krest bitter lemon may achieve very high efficacy if used as post-coital douche, especially in the impoverished, densely populated Third World.

PIP: Researchers at Obafemi Awolowo University in Ile-Ife, Nigeria, collected semen samples from 7 healthy men 25-30 years old who had abstained from sex for at least 5 days in order to examine the spermicidal action of 4 soft drinks (Krest bitter lemon, Afri-Cola, Coca-Cola, and Pepsi-Cola), the effect of increased temperature of the drinks on spermicidal action, and the effect of changing the soft drinks from an acid, as it comes from the factory, (ph 2.4) to an alkaline (pH 7.5). Increasing the temperature of the soft drinks from room temperature (22 degrees Celsius) to body temperatures (37 degrees Celsius) did not significantly change the spermicidal action any of the soft drinks. All soft drinks with an acid pH, except Coca-Cola, had a significantly lower percent of sperm motility than those with an alkaline pH (0-42.3% vs. 20-52.1%; p .001). In fact, Krest bitter lemon in its factory form (acid pH) completely immobilized all spermatozoa within 1 minute after the researchers diluted the semen with the soft drink. Alkaline Coca-Cola had a significantly lower percent of sperm motility than did acid Coca-Cola (35.8% vs. 46.5%; p .001). Other than Krest bitter lemon, the significant decreases in sperm motility were not enough to prevent pregnancy. These findings indicated that researchers should test Krest bitter lemon for effectiveness as a postcoital contraceptive. If indeed it proves effective, it has great potential as such a contraceptive among the poor in the densely population developed countries since it is readily available and inexpensive.

MeSH terms

  • Adult
  • Beverages* / adverse effects
  • Citrus*
  • Humans
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Male
  • Sperm Motility / drug effects*
  • Temperature