A study published this month in the science journal PLOS ONE, found that compared to other forms of birth control, consistent condom use promotes a healthy pH balance and the growth of beneficial bacteria in the vagina.
The women in this study who used condoms had larger amounts of beneficial microbes known as lactobacillus. These microbes produce lactic acid and hydrogen peroxide, which help the vagina maintain an average pH of 4.5. This "acid buffer system" helps block harmful bacteria from surviving in the vagina and causing infections.
Specifically, lactobacillus is thought to help prevent bacterial vaginosis (BV), which causes itching, discharge, and a foul odor. Lactobacillius has also been linked to a decreased risk of HIV infection.
Researchers from Beijing Friendship Hospital recruited 164 healthy, married women in China between the ages of 18 and 45, who did not use hormonal birth control. These women were divided into groups based on their non-hormonal birth control method of choice: 72 used condoms, 57 used IUDs, and 35 used the "rhythm method." The presence of lactobacillus was significantly higher in the condom group.
The researchers believe that condoms help the vagina maintain its natural acidic defenses by reducing the vagina's exposure to semen, which has a pH of 7 to 8.
Read the full study at plosone.org