Throw that M&M in the trash. You know, the blue one you dropped on the floor but picked up two seconds later. You thought the “five-second” rule – food that falls on the floor is safe to eat if you grab it in less than five seconds – was based on science.

It’s not. According to a study in , eating dropped food can pose a risk for ingesting bacteria, which can cause gastrointestinal disease. And the time that food sits on the floor doesn’t alter the risk of contamination. Factors that influence risk and rate of bacterial transfer include the floor, food and bacteria types, as well as how long the bacteria themselves have been on the floor.

Scientists tested salmonella placed on wood, tile or carpet, and dropped food on surfaces for five, 30 or 60 seconds. More than 99 percent of bacteria were transferred almost immediately. There was no difference by the time of contact. The carpet transferred less bacteria, but with no difference in contact time.

As few as 10 salmonella bacteria can cause a bout of gastroenteritis, but thousands of bacteria remained on the tested surfaces after 24 hours, and hundreds survived on the surfaces for as long as four weeks. The five-second rule is feeling a little less feasible now, wasted M&Ms notwithstanding.

Have you spent a lifetime adhering to the five-second rule? I have -- until now. Let me know here.