Interfering with how the medicine is digested and absorbed by the body. For example, milk blocks iron absorption in the stomach. Calcium found in dairy products can bind some medications, such as iron supplements and some antibiotics (Cipro and Levaquin, a quinolone.)
Pros of elongated: much more comfortable for adults. I would definitely choose it for the master bathroom. Pros of round: easier for very young children to use due to the smaller opening in the seat. Also, there are code requirements of how much foot space you need in front of a toilet.
The standard measurement is 5 1/2 inches between the holes. Hold the measuring tape at the center front of the toilet bowl and stretch it to the center of the hinges between the post holes. Record the measurement on paper. Shop for a round seat if your measurement was approximately 16 1/2 inches. Look for an elongated toilet seat if you measured a length of about 18 1/2 inches.