Why does drinking water feel so good when you're thirsty?

Why does drinking water feel so satisfying when you're parched? The pleasure of drinking water, particularly when we're thirsty, is rooted in intricate biochemical reactions rewarding rehydration and quenching thirst. Patricia Di Lorenzo, a psychology professor at Binghamton University, describes this experience as hedonic, stating that water tastes exceptionally satisfying when thirst hits. But why exactly is this the case?

Thirst emerged as you exercise intensely and sweat heavily, depleting blood volume. This decrease sets off neurons in exposed brain regions, beyond the protective blood-brain barrier, signaling the urge to drink. Yuki Oka from Caltech emphasizes the rapid response needed to avoid dehydration, involving the brain areas: subfornical organ (SFO), organum vasculosum lamina terminalis (OVLT), and median preoptic nucleus (MnPO). Oka's 2018 study highlighted the MnPO's role in forwarding thirst signals from the SFO and OVLT.

Remarkably, as you drink, neurotransmitter dopamine releases immediately, long before full rehydration. This rush, linked to reward-seeking and motivation, explains why actions satisfying vital needs are enjoyable. Oka discovered through a 2019 mice study that actual drinking—not merely quenching thirst—triggers dopamine, explaining why drinking water is more rewarding than IV fluids.

Beyond gulping water, which signals the MnPO that the body is rehydrating, processes after water reaches the gut further mitigate thirst sensation. A hormonal rise, vasoactive intestinal peptide (VIP), responds to the changed salt-to-water blood ratio, hinting satisfaction to the brain. Despite this understanding, many aspects of VIP and related processes remain undiscovered, an area Oka is exploring.

Ensuring ongoing balance, the intricate thirst-satisfaction responses may have evolved beyond individual survival, potentially fostering group survival by encouraging resource sharing under scarcity—though this hypothesis still awaits experimental verification.

Earlier, SSP wrote about gamma radiation in thunderstorms: new insights.