Sex Differences in Salt Appetite: Perspectives from Animal Models and Human Studies

Abstract

Salt ingestion by animals and humans has been noted from prehistory. The search for salt is largely driven by a physiological need for sodium. There is a large body of literature on sodium intake in laboratory rats, but the vast majority of this work has used male rats. The limited work conducted in both male and female rats, however, reveals sex differences in sodium intake. Importantly, while humans ingest salt every day, with every meal and with many foods, we do not know how many of these findings from rodent studies can be generalized to men and women. This review provides a synthesis of the literature that examines sex differences in sodium intake and highlights open questions. Sodium serves many important physiological functions and is inextricably linked to the maintenance of body fluid homeostasis. Indeed, from a motivated behavior perspective, the drive to consume sodium has largely been studied in conjunction with the study of thirst. This review will describe the neuroendocrine controls of fluid balance, mechanisms underlying sex differences, sex differences in sodium intake, changes in sodium intake during pregnancy, and the possible neuronal mechanisms underlying these differences in behavior. Having reviewed the mechanisms that can only be studied in animal experiments, we address sex differences in human dietary sodium intake in reproduction, and with age.

Estrogen Receptor Beta Mediates the Dipsogenic Effect of Estradiol in Ovariectomized Female Rats

“…We, therefore, investigated whether in the absence of food, estradiol also increases saline intake. As previously reported, when given both water and 1.5% saline, approximately 75% of the total fluid intake was from saline [27,28,48]. In support of this hypothesis, EB increased both saline intake and licks for saline during the 24 h test period when OVX rats were not provided food.…”

Salt-Intake-Related Behavior Varies between Sexes and Is Strongly Associated with Daily Salt Consumption in Obese Patients at High Risk for MASLD

“…In our cohort, we observed sex-specific differences not only in daily salt intake but also in salt-intake-related behavior, with men showing higher daily salt intake and lower salt awareness compared to women. Women are reported to have a 9–11% lower salt intake worldwide, which is suggested to be associated with their lower calorie intake [ 36 ]. In NHANES data, an age–gender interaction for adding table salt suggests that younger women (<30 years) tend to add salt more frequently than men, but after age 30, men more often add salt compared to women [ 36 ].…”

“…Women are reported to have a 9–11% lower salt intake worldwide, which is suggested to be associated with their lower calorie intake [ 36 ]. In NHANES data, an age–gender interaction for adding table salt suggests that younger women (<30 years) tend to add salt more frequently than men, but after age 30, men more often add salt compared to women [ 36 ]. In our cohort, we also observed an age-dependent effect on salt-related behavior, indicating higher salt awareness with increasing age.…”

Inhibition of salty taste and sodium appetite by estrogens in spontaneously hypertensive rats

“…Hormones play a significant role in inducing or constraining sodium intake in humans and rats ( Santollo et al, 2023 ). This role involves the organization of future behavior from gestation and birth onward, in addition to the immediate effect of hormones on the ingestion of salt ( Epstein, 1991 ; Mecawi et al, 2015 ).…”