Perceived intensity for sweeteners decreases 2–5% per year

A Common Genetic Influence on Human Intensity Ratings of Sugars and High-Potency Sweeteners
Twin Research and Human Genetics / Volume 18 / Issue 04 / August 2015, pp 361-367
Liang-Dar Hwanga, et al
http://journals.cambridge.org/action/displayAbstract?aid=9884832

The perception of sweetness varies among individuals but the sources of this variation are not fully understood. Here, in a sample of 1,901 adolescent and young adults (53.8% female; 243 MZ and 452 DZ twin pairs, 511 unpaired individuals; mean age 16.2 ± 2.8, range 12–26 years), we studied the variation in the perception of sweetness intensity of two monosaccharides and two high-potency sweeteners: glucose, fructose, neohesperidine dihydrochalcone (NHDC), and aspartame. Perceived intensity for all sweeteners decreased with age (2–5% per year) and increased with the history of otitis media (6–9%). Males rated aspartame slightly stronger than females (7%). We found similar heritabilities for sugars (glucose: h2 = 0.31, fructose: h2 = 0.34) and high-potency sweeteners (NHDC: h2 = 0.31, aspartame: h2 = 0.30); all were in the modest range. Multivariate modeling showed that a common genetic factor accounted for >75% of the genetic variance in the four sweeteners, suggesting that individual differences in perceived sweet intensity, which are partly due to genetic factors, may be attributed to a single set of genes. This study provided evidence of the shared genetic pathways between the perception of sugars and high-potency sweeteners.

cited by:
http://www.npr.org/sections/thesalt/2015/07/24/425609156/the-gene-for-sweet-why-we-dont-all-taste-sugar-the-same-way

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Vegetable intake & genetic variation in taste

Vegetable Intake in College-Aged Adults Is Explained by Oral Sensory Phenotypes and TAS2R38 Genotype.
Chemosens Percept. 2010 Dec 1;3(3-4):137-148.
Duffy VB, et al.
http://www.ncbi.nlm.nih.gov/pubmed/21157576

Taste and oral sensations vary in humans.
Some of this variation has a genetic basis, and two commonly measured phenotypes are the bitterness of propylthiouracil (PROP) and the number of fungiform papillae on the anterior tongue.
While the genetic control of fungiform papilla is unclear, PROP bitterness associates with allelic variation in the taste receptor gene, TAS2R38. The two common alleles are AVI and PAV (proline, alanine, valine, and isoleucine); AVI/AVI homozygotes taste PROP as less bitter than heterozygous or homozygous PAV carriers.

In this laboratory-based study, we determined whether taste of a bitter probe (quinine) and vegetable intake varied by taste phenotypes and TAS2R38 genotype in healthy adults (mean age=26 years).
Vegetable intake was assessed via two validated, complementary methods: food records (Food Pyramid servings standardized to energy intake) and food frequency questionnaire (general intake question and composite vegetable groups). Quinine bitterness varied with phenotypes but not TAS2R38; quinine was more bitter to those who tasted PROP as more bitter or had more papillae.
Nontasters by phenotype or genotype reported greater consumption of vegetables, regardless of type (i.e., the effect generalized to all vegetables and was not restricted to those typically thought of as being bitter).
Furthermore, nontasters with more papillae reported greater vegetable consumption than nontasters with fewer papillae, suggesting that when bitterness does not predominate, more papillae enhance vegetable liking.
These findings suggest that genetic variation in taste, measured by multiple phenotypes or TAS2R38 genotype, can explain differences in overall consumption of vegetables, and this was not restricted to vegetables that are predominantly bitter.

cited by:
http://www.npr.org/blogs/thesalt/2014/10/01/352771618/from-kale-to-pale-ale-a-love-of-bitter-may-be-in-your-genes

Polymorphisms influence alcohol taste

Polymorphisms in TRPV1 and TAS2Rs Associate with Sensations from Sampled Ethanol.
Alcohol Clin Exp Res. 2014 Sep 25.
Allen AL, McGeary JE, Hayes JE.
http://www.ncbi.nlm.nih.gov/pubmed/25257701

BACKGROUND:
Genetic variation in chemosensory genes can explain variability in individual’s perception of and preference for many foods and beverages.
To gain insight into variable preference and intake of alcoholic beverages, we explored individual variability in the responses to sampled ethanol (EtOH).
In humans, EtOH elicits sweet, bitter, and burning sensations.
Here, we explore the relationship between variation in EtOH sensations and polymorphisms in genes encoding bitter taste receptors (TAS2Rs) and a polymodal nociceptor (TRPV1).

METHODS:
Caucasian participants (n = 93) were genotyped for 16 single nucleotide polymorphisms (SNPs) in TRPV1, 3 SNPs in TAS2R38, and 1 SNP in TAS2R13. Participants rated sampled EtOH on a generalized Labeled Magnitude Scale. Two stimuli were presented: a 16% EtOH whole-mouth sip-and-spit solution with a single time-point rating of overall intensity and a cotton swab saturated with 50% EtOH on the circumvallate papillae (CV) with ratings of multiple qualities over 3 minutes. Area-under-the-curve (AUC) was calculated for the time-intensity data.

RESULTS:
The EtOH whole-mouth solution had overall intensity ratings near “very strong.” Burning/stinging had the highest mean AUC values, followed by bitterness and sweetness. Whole-mouth intensity ratings were significantly associated with burning/stinging and bitterness AUC values on the CV. Three TRPV1 SNPs (rs224547, rs4780521, rs161364) were associated with EtOH sensations on the CV, with 2 (rs224547 and rs4780521) exhibiting strong linkage disequilibrium. Additionally, the TAS2R38 SNPs rs713598, rs1726866, and rs10246939 formed a haplotype, and were associated with bitterness on the CV. Last, overall intensity for whole-mouth EtOH associated with the TAS2R13 SNP rs1015443.

CONCLUSIONS:
These data suggest genetic variation in TRPV1 and TAS2Rs influence sensations from sampled EtOH and may potentially influence how individuals initially respond to alcoholic beverages.

KEYWORDS:
Bitterness; Burn; Ethanol; TRPV1; Taste Phenotype

journalistic version:
http://www.npr.org/blogs/thesalt/2014/10/01/352771618/from-kale-to-pale-ale-a-love-of-bitter-may-be-in-your-genes