Applied nutritional investigationEffects of smell loss (hyposmia) on salt usage
Introduction
Salt intake can activate neural, endocrine, paracrine, and vascular mechanisms that have the potential to increase arterial pressure, induce hypertension, and play a role in induction of cardiovascular disease (CVD) [1]. Because “taste loss” or decreased flavor perception is a common complaint among patients with smell loss (hyposmia) [2], the question of whether or not these individuals exhibit an increased salt preference or salt appetite is of importance as there may be as many as 21 million people in the United States with hyposmia [3].
To our knowledge, there are few reported data relating salt intake among patients with hyposmia. There are studies reporting that salt intake may decrease after olfactory bulbectomy in sheep [4] or in patients as they age [5], [6], [7], although other investigators did not find this latter event to occur [8]. Many studies, however, have reported that sodium deprivation in humans [6], [9] or in animals [10], [11] enhances intake and preference for sodium solutions and enhances the appeal of reduced sodium foods. Restricting exposure to salty foods has been reported to enhance the appeal of reduced sodium foods [12]. Genetic factors related to salt taste [13], [14] and the finding of specific salt receptors [15] have also allowed a greater physiological perspective on salt intake behaviors. Patients with smell loss have been previously reported to use larger quantities of salt, thereby increasing the risk for developing hypertension [16]. Odors have been reported to increase salt intensity by as much as 25% [17], suggesting that loss of odor perception may be associated with decreased perception of salt intensity.
We have observed a common, recurrent event among patients evaluated at The Taste and Smell Clinic in Washington, D.C., which suggested that hyposmia might be an important sensory abnormality altering salt usage. Patients with this symptom commonly said they increased their use of table salt and exhibited a profound craving for salty foods after the loss of smell. This increased salt usage appeared to occur without any consistent abnormality in taste, per se. At first glance, this seemed surprising because salt taste bears no direct relation to loss of smell. However, patients with hyposmia complained of a decreased ability to obtain flavor from food and said they increased salt usage as a way to compensate. In this way, they said, the additional salt gave more “taste” or flavor to otherwise perceived bland food. To test the validity of these observations, we quantitated the amount of salt reportedly consumed by patients with hyposmia and measured their use of table salt and the frequency of their consumption of salty foods.
We also studied the incidence of hypertension in these patients. Indeed, these latter studies were related to reports that hypertensive patients preferred more highly salted fluids than controls [18], [19], [20], were less sensitive to the taste of salt [21], and thereby consumed more salt [22]. There is considerable literature relating salt intake to hypertension. Although the association between salt intake and hypertension is not clear-cut and the mechanisms underlying this relationship are unclear, several aspects of this relationship have been emphasized in recent years including genetic, renal pathophysiological, and sensory factors [23], [24]. With respect to the latter aspect, salt taste sensitivity was initially considered to play a role in controlling salt consumption in animals [25] and humans [22]. Some investigators hypothesized that hypertensive individuals consumed more salt because they could not taste it as well as individuals with normal blood pressure [21], [26], [27], however, other studies did not agree with these results [8].
Section snippets
Participants
Participants in the study were 97 consecutive patients with hyposmia and 27 normal volunteers (control group). The patients were evaluated at The Taste and Smell Clinic in Washington, D.C. for taste and/or smell dysfunction [2]. The 56 patients selected for this study all had hyposmia (v.i.) and normal taste acuity (vide infra). The 41 patients excluded from the study either did not exhibit hyposmia (e.g., they had either hypogeusia or some form of dysgeusia or dysosmia [2], [28], [29]) or had
Results
Eighteen (32%) of the 56 patients reported increased salt use at the time they were evaluated for their hyposmia. These patients were labeled “increased users” to differentiate them from the majority of patients (68%) who did not report an increase in their salt usage. They were labeled “non-changers.”
Increased users estimated that their salt usage increased over a range from two to five times that before hyposmia onset with an estimated mean of 2.8.
The total salt score of increased users was
Discussion
The results of this study confirm our clinical observations that some patients with hyposmia (with normal taste acuity) increase their use of salt and consumption of salty foods after loss of smell. These patients had high salt scores, frequently salted their foods before tasting, frequently added salt to their food at the table, rated their salt use as moderate to heavy, and frequently consumed salty foods.
The mechanism(s) of this increased salt usage in the face of normal taste acuity is
Conclusion
Increased salt usage occurs in about one-third of patients with hyposmia putatively due to a compensatory mechanism by which adding more salt to food and eating more salt-laden foods increases their ability to obtain more food flavor.
Acknowledgment
The author acknowledges D. Mattes-Kulig for her major assistance in performance of this study.
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