Do scientists really believe that the moon’s phases affect human blood flow?
Absolutely not. People get confused about the size scale at which various effects work. What results are urban legends, superstitions, and false beliefs propagated for centuries. The moon’s gravitational effects on tides is a large-scale phenomenon, far too weak to affect the fluids in a human. Similarly, distant gravitational masses such as other planets in the solar system have no effect on earth or its occupants — invalidating astrology. Likewise the Coriolis forces that affect winds by making air masses circulate are far too weak to affect the circulation of water going down a drain. When you do the calculations based on laws of physics these facts are readily verified.