Plus, five expert-approved ways to clean them.  

If you think about it, your trusty water bottle travels with you far and wide: to the office, the gym, and even on vacation, which means you shouldn't be surprised to learn that reusable water bottles come in contact with a lot of germs. A new study suggests you should really start cleaning your bottle out regularly if you don’t already, as these otherwise wonderful, eco-friendly lifesavers can also play host to harmful bacteria, including E. coli.

A team of microbiologists from Brazil randomly selected 30 members of two local fitness centers to have their reusable bottles tested for contamination, while also testing 30 new bottles that had never been used. Their research showed none of the new shaker bottles were contaminated yet, while 90 percent of the randomly selected shaker bottles were contaminated with some form of potentially harmful bacteria. E. coli and Staphylococcus aureus were the most prevalent types of bacteria found in these bottles, with 17 and 27 percent respectively.

This isn't the first time research has illustrated the cringe-worthy reason we all should clean our bottles regularly. An additional study posted by showed drinking from an unwashed reusable water bottle can be worse for you than licking your dog’s chew toy.

The study noted plastic is the worst choice for reusable water bottles, as it can be a harder material to properly clean compared to stainless steel, metal, and glass options.

More sources of foodborne illnesses you should avoid:

"Bacteria can build up within the water bottle in a moist environment and nobody wants to drink bacteria laden water," Rudolph Bedford, MD, gastroenterologist at Providence Saint John's Health Center in Santa Monica, California, told Health. "Clean it daily. The problem is most people rinse with water only."

But don't toss your water bottle just yet! There are several manageable ways you can prevent contamination and stay healthy, while also doing your part to avoid contributing to plastic pollution.

Philip Tierno, Ph.D., professor of microbiology and pathology at the NYU School of Medicine, told Runner’s World contamination most likely comes from handling. Tierno advises washing your hands after using the restroom, touching your face, and before mixing a drink for the gym. He also advises running your water bottle through the dishwasher daily, if the manufacturer has made it clear that it's safe to do so.

Other ways to properly wash your water bottle, according to Health, include 3 percent hydrogen peroxide, which can help eliminate any kind of residue or odor, as well as a vinegar rinse, water cleansing tablets, and a good dousing of dish soap and water.