Why do you swig bitter, dark roast coffee or hoppy beer while your coworker guzzles sweet cola?
Previous study….
Coffee, tea and alcohol are widely consumed beverages with bitter taste1 and have been implicated in both beneficial and adverse health effects2,3.
Individual differences in metabolizing caffeine4,5 and ethanol6,7,8,9,10 present in these beverages determine their consumption level, whereas the influence of taste factors remains unclear.
The relationship between the perception of bitter compounds, such as propylthiouracil (PROP), quinine, and caffeine, and the consumption level of these bitter beverages have been inconsistent across observational studies11,12,13,14,15,16,17,18,19,20,21,22.
As performing taste tests is a resource-intensive process, these investigations likely lacked sufficient power to convincingly rule out moderate effects.
Potential confounders or illnesses that both affect taste perception and consumption in these studies limits their ability to provide unbiased causal effects.
Fortunately, these issues can be overcome by recent advances in taste genetics and statistical methodology.
Heritability for the perceived intensity of PROP, quinine, and caffeine have been estimated to be 0.73, 0.40, and 0.36 in classical twin studies23,24.
Furthermore, candidate gene and genome-wide association studies (GWAS) have pinpointed precise genetic factors25,26,27, including SNPs within the bitter taste receptor gene TAS2R38 for PROP and SNPs within the cluster of bitter taste receptors genes on chromosome 12 for quinine and caffeine.
Identification of these genetic variants provides an opportunity to apply Mendelian randomization (MR), a technique commonly used in disease epidemiology, to test the causal relationship between bitter taste and an outcome of interest using genetic variants (e.g. SNPs) as instrumental variables (IVs).
The fundamental principle of MR is based on Mendel’s Law of Independent Assortment whereby genetic variants are shuffled at meiosis, conceptually mimicking a “natural” randomized trial28,29,30.
Since genetic variants are randomized at conception, they can be used as risk factor instrumental variables that are generally free from confounding and reverse causality to evaluate the relationship of a risk factor on a specific outcome of interest31,32.
The new study….
Scientist Marilyn Cornelis searched for variations in our taste genes that could explain our beverage preferences because understanding those preferences could indicate ways to intervene in people’s diets.
To Cornelis’ surprise, her new Northwestern Medicine study showed taste preferences for bitter or sweet beverages aren’t based on variations in our taste genes, but rather genes related to the psychoactive properties of these beverages.
“The genetics underlying our preferences are related to the psychoactive components of these drinks,” said Cornelis, assistant professor of preventive medicine at Northwestern University Feinberg School of Medicine.
“People like the way coffee and alcohol make them feel. That’s why they drink it. It’s not the taste.”
The paper will be published May 2 in Human Molecular Genetics.
The study highlights important behavior-reward components to beverage choice and adds to our understanding of the link between genetics and beverage consumption – and the potential barriers to intervening in people’s diets, Cornelis said.
Sugary beverages are linked to many diseases and health conditions.
Alcohol intake is related to more than 200 diseases and accounts for about 6 percent of deaths globally.
Cornelis did find one variant in a gene, called FTO, linked to sugar-sweetened drinks. People who had a variant in the FTO gene – the same variant previously related to lower risk of obesity — surprisingly preferred sugar-sweetened beverages.
“It’s counterintuitive,” Cornelis said. “FTO has been something of a mystery gene, and we don’t know exactly how it’s linked to obesity. It likely plays a role in behavior, which would be linked to weight management.”
“To our knowledge, this is the first genome-wide association study of beverage consumption based on taste perspective,” said Victor Zhong, the study’s first author and postdoctoral fellow in preventive medicine at Northwestern. “
It’s also the most comprehensive genome-wide association study of beverage consumption to date.”
How the study worked
Beverages were categorized into a bitter-tasting group and a sweet-tasting group. Bitter included coffee, tea, grapefruit juice, beer, red wine and liquor.
Sweet included sugar-sweetened beverages, artificially sweetened beverages and non-grapefruit juices.
This taste classification has been previously validated.
The study highlights important behavior-reward components to beverage choice and adds to our understanding of the link between genetics and beverage consumption – and the potential barriers to intervening in people’s diets, Cornelis said.
The image is in the public domain.
Beverage intake was collected using 24-hour dietary recalls or questionnaires. Scientists counted the number of servings of these bitter and sweet beverages consumed by about 336,000 individuals in the UK Biobank.
Then they did a genome-wide association study of bitter beverage consumption and of sweet beverage consumption. Lastly, they looked to replicate their key findings in three U.S. cohorts.
Alan Kuang is also a Northwestern author on the paper.
Source:
Northwestern University
Media Contacts:
Marla Paul – Northwestern University
Image Source:
The image is in the public domain.
Original Research: Closed access
“A genome-wide association study of bitter and sweet beverage consumption”. Victor W Zhong, Alan Kuang, Rebecca D Danning, Peter Kraft, Rob M van Dam, Daniel I Chasman, Marilyn C Cornelis.
Human Molecular Genetics. doi:10.1093/hmg/ddz061
