Can salt reduce bitterness, and does the effect depend on what tastes bitter?

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The experiments tested how bitterness and saltiness change when a salt and a bitter compound are mixed at different concentrations. Participants rated the strength of both tastes. The central finding was that salts usually reduced bitterness, but not uniformly.

The researchers then examined urea, a chemical compound used as a bitter-tasting substance in these tests, more closely. Three sodium salts—sodium chloride, sodium acetate and sodium gluconate—reduced its bitterness comparably, even though they tasted progressively less salty. Lithium chloride also reduced urea’s bitterness, whereas potassium chloride did not. This pattern suggested that the sodium or lithium component mattered more than perceived saltiness alone for this effect.

The interaction generally did not work equally in reverse: bitterness suppression was not accompanied by a comparable reduction in saltiness. Only magnesium sulphate and amiloride reduced sodium chloride’s saltiness at intermediate concentrations; none of the tested bitter compounds affected its saltiness at high sodium chloride concentrations.

The authors suggested that much of sodium’s effect on urea bitterness occurs at an early stage of taste processing. This was an interpretation, not a demonstrated mechanism, and whether it extends to other bitter substances remained uncertain. These solution experiments do not establish how much salt would reduce bitterness in a particular food.