Evidence that Humans Can Taste Glucose Polymers

Abstract

The sense of taste is essential for identifying potential nutrients and poisons. Accordingly, specialized taste receptor cells are activated by food-derived chemicals. Because of its importance in the human diet, oral detection of starch, or its degradation products, would presumably be highly beneficial. Yet, it has long been assumed that simple sugars are the only class of carbohydrates that humans can taste. There is, however, considerable evidence that rodents can taste starch degradation products (i.e., glucose polymers composed of maltooligosaccharides with 3-10 glucose units and maltopolysaccharides with >10 glucose units) and that their detection is independent of the sweet taste receptor, T1R2/T1R3. The present study was designed 1) to measure individual differences in human taste perception of glucose polymers, 2) to understand individual differences in the activity of salivary α-amylase, and 3) to investigate the role that salivary α-amylase may play in the taste perception of glucose polymers. In the first experiment, subjects rated taste intensity of glucose, sucrose, NaCl, and glucose polymers of various chain lengths, while their noses were clamped. Saliva samples from the subjects were also collected and their salivary α-amylase activity was assayed. Results showed that the perceived intensities of glucose, sucrose, and NaCl were significantly correlated (r = 0.75-0.85, P < 0.001), but not with the longer chain glucose polymers, whereas intensity ratings of all glucose polymers were highly correlated with one another (r = 0.69-0.82, P < 0.001). Importantly, despite large individual differences in α-amylase activity among subjects, responsiveness to glucose polymers did not significantly differ between individuals with high and low α-amylase activity. A follow up experiment was conducted to quantify the concentrations of glucose and maltose that were inherently present in the glucose polymer stimuli and to determine whether the amounts were within a perceptually detectable range. Results revealed that the amounts of simple sugars present in the test stimuli were trivial and were mostly at an undetectable level. These data together provide strong evidence that humans can taste glucose polymers and that the responsiveness to glucose polymers is independent of that to simple sugars.

The Associations Between Oral Complex Carbohydrate Sensitivity, BMI, Liking, and Consumption of Complex Carbohydrate Based Foods

“…Our findings replicate previous findings signifying that humans may perceive complex carbohydrates in the oral cavity (Lapis et al, 2014(Lapis et al, , 2016; and contest the knowledge where complex carbohydrates have been assumed to be invisible to the human palate system (Feigin, Sclafani, & Sunday, 1987;Hettinger, Frank, & Myers, 1996). Consistent with our previous findings (Low et al, 2017a), there was considerable interindividual variation for oral complex carbohydrate sensitivity among this sample, and individuals were able to be classified as more or less sensitive or as those who experienced high or low intensity to complex carbohydrate across both measures (DT and ST).…”

“…It is widely believed that the human taste system consists of five basic tastes: sweet, sour, salty, bitter, umami, and much recent evidence supports a sixth taste responsive for fatty acids (Chalé‐Rush, Burgess, & Mattes, ; Mattes, , ; Newman, Haryono, & Keast, ; Newman, Bolhuis, Torres, & Keast, ; Newman & Keast, ; Running, Craig, & Mattes, ; Stewart & Keast, ; Stewart et al., ; Stewart, Feinle‐Bisset, & Keast, ; Tucker, Edlinger, Craig, & Mattes, ). More recent psychophysical studies suggest that humans may perceive complex carbohydrates, independent of sweet taste (Lapis, Penner, Balto, & Lim, ; Lapis, Penner, & Lim, , ; Low, Lacy, McBride, & Keast, ). That is, sensitivity of simple carbohydrates (glucose and sucrose) were significantly correlated with each other, but not with sensitivity of complex carbohydrates (Lapis et al., , ).…”

“…More recent psychophysical studies suggest that humans may perceive complex carbohydrates, independent of sweet taste (Lapis, Penner, Balto, & Lim, ; Lapis, Penner, & Lim, , ; Low, Lacy, McBride, & Keast, ). That is, sensitivity of simple carbohydrates (glucose and sucrose) were significantly correlated with each other, but not with sensitivity of complex carbohydrates (Lapis et al., , ).…”

Human amylase gene copy number variation as a determinant of metabolic state

“…In humans, salivary amylase may also be implicated in stimulation of the CPIR response and improved glucose tolerance following starch ingestion. Starch breakdown products may be detected in the oral cavity, by either or both the T1Rindependent metabolic pathway and the polysaccharide receptor that can bind short-chain oligosaccharides [14,32,76]. CPIR triggered by elevated levels of salivary amylase may have provided an evolutionary advantage as starch consumption increased among human populations, thereby promoting AMY1 CNV expansion within the population [32].…”

Starch digestion in the upper gastrointestinal tract of humans

“…The work of Lapis et al, utilized a series of low viscosity dextrins in a series of psychophysical tests. Within these tests, it was noted that all dextrins, regardless of chain length elicited a “taste” perception immediately upon ingestion and that the activity of salivary amylase noted within participants did not affect the intensity of the response elicited . The authors credited this action to the ability of humans to chemically sense glucose polymers, although the potential for texture/osmolarity‐based sensing cannot be entirely ruled out.…”