Some people carry a genetically driven "salt tooth" that could affect how heavily they season their food, potentially endangering their heart, a new study suggests.
Perception of bitter flavours
Genetic variations cause some people to be more keenly aware of bitter flavours, said lead researcher Jennifer Smith, a doctoral student at the University of Kentucky College of Nursing.
These people are about twice as likely to exceed the daily limit of salt recommended by heart health specialists, according to study findings presented at the American Heart Association annual meeting in New Orleans.
The research centres on a gene called TAS2R38. Variations of this gene have been shown to enhance a person's perception of bitter flavours.
"We were looking at a gene that codes for taste receptors," Smith said. "People with one genotype will taste bitter more keenly than people who have the other genotype."
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Previous studies have shown that people carrying those genetic variations of TAS2R38 are more likely to avoid heart-healthy foods that can taste bitter, like broccoli or dark leafy greens, the researchers said.
Smith decided to test whether this gene would lead people to use more salt in their daily diet. Eating too much salt can lead to high blood pressure, which increases a person's risk for heart attack and stroke.
Her team analysed the diets of 407 people in rural Kentucky who had two or more heart disease risk factors. The researchers also did genetic testing to see whether participants carried the gene variation that enhances bitter taste.
"We found people who tasted bitter more keenly were in fact 1.9 times more likely to be non-adherent to the sodium guidelines," she said.
US dietary guidelines recommend no more than 2.3 grams of salt per day.
The researchers have different theories about why people with these genetic variants seem to eat more salt.
It could be that they taste salt more intensely and enjoy it more, causing them to prefer heavily salted foods, Smith said.
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Or it could be that people use salt to mask the bitter taste of some foods, she added.
"There are alternatives you can use to flavour foods, and we need to begin investigating those," Smith said. "We can start to look if there are different types of spices or seasonings we can add instead of salt to offset the bitter taste. For example, with bitter vegetables, you can use a little bit of sugar rather than salt to offset the bitter."
A flavour alternative
The findings are fascinating but "very preliminary", said Dr Lawrence Appel. He's a professor of medicine and director of the Welch Centre for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medical Institutions in Baltimore.
"Because bitterness is amplified, these people may need some other flavour alternative to mitigate the gene-induced bitterness," said Appel, a spokesman for the American Heart Association. "But you always need replication [studies], because there are always a lot of chance findings in genetic research. It's definitely what I like to call preliminary science."
Another study presented at the AHA meeting found that most US adults consume too much salt, based on 24-hour urinary tests.
Overall, adults excreted more than 3.6 grams of sodium in their urine on a given day, far higher than the 2.3-gram dietary limit, researchers found. Men excreted about 4.2 grams a day on average; women, 3.1 grams, according to the study.
"We still consume vastly more sodium than we need to, and it does adversely affect blood pressure. Especially as we age, it becomes increasingly important to cut back," Appel said. "Whether or not you have this gene, sodium reduction is good for you."
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Research presented at medical meetings is typically considered preliminary, because it has not had the same scrutiny as studies in peer-reviewed journals.
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