Can Eating Activia Have an Effect on INR and Coumadin (warfarin)?

I am a nurse and work in an anticoagulation clinic, and one of my clients mentioned that they were taking Activia every day. Their INR went up from 3.3 to 5.12. I was wondering if the Activia had something to do with this, or the fact that she was eating a lot of fresh fruit and now has been dealing with diarrhea. I realize the diarrhea has a part in the increase, but was also wondering how Activia plays into this.

The Health meets Food Team Says...

That's an interesting question and one that I don't think we have the best research for.

We do know that the bacteria in the gut produce Vitamin K that we absorb. This is why giving some antibiotics can cause a change in INR (of course, some other antibiotics such as macrolides may have an effect on the bioavailability of warfarin). If there are more gut bacteria from the probiotics in Activia and other yogurt, this could have an effect. The key would be stability: eating the same amount of yogurt daily and adjusting warfarin accordingly.

The fruit might be an issue if she had an increase in fiber over what she might have been taking causing more rapid transit through the gut. If the fruit is blueberries, that also might be an issue as blueberries do contain a moderate amount of Vitamin K. The diarrhea may also be a factor as you say.

Thanks for writing.