Blood is mostly made up of water, as are our organs and muscles. To read specifically about edema, swelling caused by fluid retention where excess fluid is trapped in the body's tissues, see our article Edema: Causes, Symptoms and Treatments.
If you use the Amsoil Ea15K01 and the ASM oil (For 3rd gen Prius), then you can safely go 15,000 miles between oil changes. I drive 25,000 miles per year in my Prius. Amsoil backs up their products by a written warranty.
The Prius, to maintain the warranty, must have oil and oil filter changes every 5000 miles, and larger services (such as air filter changes) every 15,000 miles. I personally change my oil in both Toyotas every 3000 miles and rotate the tires every other oil change (every 6000). I do stick with the 15,000 mile intervals for the bigger 15k services. I also go to my local dealership for all service, because I know the techs, the owner of the dealership, and everyone in-between.