Dehydration! That’s according to a report from the University of Arkansas where they found even MILD dehydration makes our blood thicker, which means the heart has to work harder to pump it around the body. And that’s not all. The researchers found that being dehydrated increases levels of a certain hormone that damages the tissue lining of our blood vessels, and that tissue also plays a part in regulating blood flow. So the researchers say a good plan is to drink enough liquid so you’re using the bathroom 6 times a day, at least.