Birth control is probably the last item in your pharmaceutical arsenal that you would want to fail. Which is why some recent research on artificial sweeteners could be major cause for concern.

Researchers found that one of the most popular artificial sweeteners, the sucralose-containing Splenda, caused a decrease in stomach bacteria in rats. If so, could Splenda also decrease the effectiveness of oral contraceptives?

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Hormones, and how oral contraceptives work
Oral contraceptives work, in part, by maintaining a desired level of the hormone estrogen in the body. This constant supply of estrogen prevents the start of ovulation and the release of a fertile egg. Most oral contraceptives make use of the synthetic estrogen ethinyl estradiol to maintain these levels during a 28 day cycle. One of the problems with oral contraceptive pills, however, is that the majority of ethinyl estradiol included is metabolized by the liver before the molecule reaches its target.

Oral contraceptives, particularly those with once-a-day dosages, rely on the recycling of ethinyl estradiol metabolites back into ethinyl estradiol by "good" bacteria in the stomach, to provide a stable level of estrogen. Without this bacteria, the level of ethinyl estradiol wanes in the later hours a day, and this drop in estrogen levels could allow an undesired ovulation to begin.


Mixing antibiotics and oral contraceptives
Cases of conception while a patient is on both an antibiotic regimen and oral contraceptives are noted in medical literature. One study claims one in five women seeking out family planning services or a pregnancy cessation do so while simultaneously using oral contraceptives and antibiotics. Data revolving around this phenomenon, however, is sparse, yielding substantial debate on the topic.

There is a lingering precedent for a decrease in digestive tract bacteria, altering the behavior of birth control pills. Antibiotics can remove a large amount of the bacteria that resides within your body — a removal often experienced you though an unending need to run to the restroom several days into a course of antibiotic treatment.

For patients regularly taking birth control pills, additional oral contraceptives are often prescribed when an extended course of antibiotics is administered as a fail safe, since an interruption of contraceptive effects could be really bad for you. Plus, someone who's already sick may not be quite as likely to remember to take contraceptives on time, which could lead to a decrease in estrogen and a similar risk of health problems and pregnancy.


Splenda decreases the amount of bacteria in rats
Sucralose is the molecule in Splenda that lends a sweet taste to the product, and a 2008 Duke University study looked at the effect of Splenda intake on metabolic enzymes and digestive tract bacteria in male rats.

In the study, laboratory rats who consumed a diet containing Splenda over twelve weeks suffered up to a eighty percent decrease in digestive bacteria when compared to the control group. If this translates to the same proportions in humans, Splenda could cause a substantial decrease in digestive tract bacteria in consumers, and possibly alter levels of ethinyl estradiol in those taking oral contraceptives.


Dosages of Splenda (and thus sucralose) given to rats in the study straddled the FDA approved daily intake of sucralose, 5 milligrams per kilogram of body weight per day. Rats within the test group given the lowest amount of sucralose, 1.1 milligrams per kilogram of sucralose a day through administration of 100 milligrams of Splenda dissolved in water, experienced a 47% decrease in digestive bacteria.

In addition to that decrease in stomach bacteria, an increase in activity of P-Glycoprotein and Cytochrome P-450 is observed in the experimental groups. Increased activity of P-Glycoprotein and the two Cytochrome P-450 enzymes observed in this study, CYP3A4 and CYP2D1, can decrease the bioavailability of some orally administered pharmaceuticals, including Xanax and some statins.


A legitimate risk?
Although medical professionals are often at arms over possible interactions between antibiotics and oral contraceptives, a failure in your oral contraceptive is obviously a life-changing experience, and something worthy of mention. Most medical professionals will warn of this possible interaction and often take steps to prevent it in order to forgo future liability.

Data correlating sucralose or Splenda consumption to oral contraceptive failure is nonexistent. But it's not an extreme leap of logic to extend the decrease in bacteria observed in rat studies to a corresponding decrease human stomach bacteria and subsequently, decreased levels of ethinyl estradiol recycled from metabolites of oral contraceptives.

The amount of sucralose necessary to cause this effect in humans is completely unknown, as well as whether a sucralose-initiated wipe-out of bacteria is possible at all in humans. If you are downing 10-15 two liters of Splenda sweetened soft drinks a day while taking an oral contraceptive, however, you might be adding a contraceptive problem problem to your cola addiction.


Images from theseoduke/Flickr, griegatlanta/Flickr, and Inge Habex/CC. Sources linked within the article.