It is not mom’s fault that she is an avid believer of the myth. As it is established on two very persuasive explanations.
The first theory presents that after eating, the majority of blood is diverted to our digestive system, and away from the muscles required for swimming movements. We do not have sufficient blood to supply both actions of digesting and swimming simultaneously (Franco, 2015; Melissa Conrad Stöppler, 2014; The Conversation, 2012).
As a consequence of this shared blood supply, the stomach does not receive enough blood, leading to a series of muscle cramps causing significant discomfort and pain in the individual (Franco, 2015). This could potentially limit the person’s ability to swim and consequently put them at risk of drowning (Beth Israel Deaconess Medical Center, 2012; Franco, 2015; Kidshealth.org, 2015; Snopes.com, 2015). Similarly, it is presumed and misconstrued that if the limbs do not get adequate blood flow, the individual is also exposed to a high risk of losing control under the water and drowning (The Conversation, 2012).
Other supporters of the myth – Kibayashi, Nakao & Shimada (2011) also state that the presence of food content in the stomach is a factor linked to accidental drowning. However, their rationale is that blood diverts and piles up in the stomach and intestines to aid in digestion. This may decrease overall blood flow to other parts of the body, that are not associated with digestion. In particular, altered cerebral blood flow leads to a loss of consciousness due to inadequate blood flow to the brain. That is when the brain loses control of the body’s movements, exposing the individual to the greater risk of drowning.