FOOD & DRINK
22/02/2019 07:45 -03 | Atualizado 25/02/2019 17:45 -03

How Genetics Are Partly To Blame For Your Food Cravings

Certain genetic markers can influence your preferences for sweet vs. salty, but you can’t blame them entirely for poor eating habits.

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A growing body of research suggests that genetics play a role in our taste preferences.

Growing up, my sister liked to eat the salt that gathers at the bottom of bags of pretzels. She still craves salty foods, and so does her 3-year-old son. On the other hand, I’ve had a lifelong sweet tooth, like our dad.

My family’s sweet and salty food cravings raise a curious question: Could genetics play a role in our flavor preferences? A growing body of research suggests a possible link.

Nanette Steinle, a University of Maryland School of Medicine associate professor of medicine and endocrinology and the diabetes section chief at the Maryland Veterans Affairs Medical Center, has studied the relationship of genetics with taste preferences and food choices.

“There are specific receptors that regulate salt taste versus sugar taste,” she said. “There aren’t large, robust studies looking at this question, but for those that are available, we do suspect that there could be a genetic component for preferences for salt, bitter, sweet.”

Steinle co-authored Genetics of Eating Behavior: Established and Emerging Concepts, a 2011 study that examined the role of genetics and the five taste profiles: sweet, bitter, salty, sour and umami. It identified some genes that can influence preferences for sweet and umami and others linked to bitter taste receptors. There are also proteins that regulate salt and water absorption in the body and are connected to salt preferences, she said.

Many researchers believe that along with taste receptors, many factors affected by genetics — including body mass index, metabolism, the brain’s reward center and the hormones involved in feeling hunger and satiety — influence food cravings. Health and nutrition experts caution, however, that genetically influenced preferences shouldn’t be viewed as excuses for poor eating habits.

The genetic markers linked to sweet and salty preferences

Scientists at 23andMe, a direct-to-consumer genetic testing company, have identified 43 genetic markers for which individuals show variants that could indicate a preference for sweet or salty foods, said Janie Shelton, a senior scientist with the company’s data collection unit. 23andMe offers a test for people to see how their genetics can be associated with preferences for sweet, salty and other types of foods.

Based on genetics, 24 percent of women prefer sweet foods over salty, compared with 2.6 percent of men.

“The genetics that were found to be linked to sweet preference over salt preference were actually linked to the genes associated with metabolism and body mass index,” Shelton said. The way people prefer certain foods and how they metabolize what they eat can be linked to weight and a tendency to be obese.

By comparison, other food preferences, like for particular ice cream flavors, are linked to the genes in the olfactory pathway, or sense of smell. Eating behaviors and personality traits, like a tendency to feel hangry, are linked to genes associated with mental health conditions and personality and well-being characteristics, she said.

“If you prefer sweet, you might have a tendency toward more high-caloric-density foods,” Shelton said. “That’s in evolutionary traits where, historically, that would have been something that helped us survive. With regard to salt, there’s a whole different metabolic pathway that has to do with how your kidneys process salt and how different mineral products are metabolized in your body. But the tendency for sweet over salty was definitely more closely linked to genes related to metabolism and body mass rather than anything that we saw linked to salt and metabolism.”

Several genes are associated with whether someone prefers salt over sugar or vice versa, and they have to do with how people metabolize food and the tendency to be overweight. One is the “famous FTO gene,” often called the “obesity gene,” Shelton said. 23andMe research has also uncovered that people with certain genotypes have a higher likelihood of preferring salty or sugary foods.

People with one variant of the FGF21 gene, associated with food regulation, were 20 percent more likely than those with another variant to seek out sugary substances, according to a separate study by the University of Copenhagen published in Cell Metabolism.

According to 23andMe genetic data, 24 percent of women probably prefer sweet foods over salty, compared with 2.6 percent of men. Geography was another variable, with people in Oregon more likely to consume sweets compared with the rest of the country, based on their genes, and people in Maine and Hawaii more likely to consume salty foods.

Genetically, however, sweet and salty preferences are “not a black and white association,” Shelton said.

“We’re saying that people with these genetic variants might lean more closely to preferring salt,” she said. “It doesn’t mean that they would never eat a piece of cake, so it tends to be a nuanced thing. The number of changes in the genome that would put you on one side of the line or the other is pretty small. We bend people into categories based on these 43 different variants, so you could be in the middle where 45 percent of people with your genetics prefer sweets and 55 percent prefer salty. If you landed where it’s more like 10 percent versus 90 percent, it might be much more strongly predicted by your genetics.”

Are sugar and salt cravings linked?

How the body processes and responds to sugar and salt can affect cravings, and James DiNicolantonio — a cardiovascular research scientist at Saint Luke’s Mid America Heart Institute in Kansas City, Missouri, and an associate editor of the British Medical Journal’s Open Heart — said there’s a likely connection between salt and sugar cravings.

Not getting enough salt can hyperactivate the brain’s reward center, increasing cravings for salt and sugar, and some people may be genetically predisposed to feel a greater reward from sugar or salt, said DiNicolantonio, the author of The Salt Fix.

The FTO gene affects levels of the hormone ghrelin, which makes people feel hungry, and leptin, which makes people feel full. Other important genes, which regulate appetite, can interfere with how satisfied we are with food intake.

The body needs salt, since it’s composed of the essential minerals sodium and chloride and the body can’t produce it, he said. But as for sugar, “our body can utilize fats and protein to create glucose,” so there’s no need to get it directly from outside sources. Refined sugar can offer a stronger reward, and it can be more addictive, increasing cravings.

Healthy kidneys regulate the salt level in the bloodstream. Still, DiNicolantonio urged people to pay attention to their salt cravings because it could signal a salt deficiency.

“For the majority of people, a salt craving is very similar to your thirst signal for water,” he said. “The whole reason why people recommend a low-salt diet is because, in some people, it lowers blood pressure a little bit, but not consuming enough water or consuming a low-water diet can also lower blood pressure. Sometimes your thirst for water can cross over or people who are deficient in salt, like athletes, will overconsume water, and some will overhydrate and develop low sodium levels in the blood.”

The Centers for Disease Control and Prevention said, however, that the majority of Americans “eat more sodium than they should — an average of more than 3,400 mg each day.” For most adults, the recommended sodium intake is less than 2,300 mg per day, equal to about a teaspoon of salt, and fewer than 10 percent of a person’s daily calories should come from added sugars, according to U.S. government dietary guidelines. The American Heart Association recommends a low-sodium diet, ideally limited to less than 1,500 mg per day.

Genetics don’t excuse poor eating habits

With food cravings, it’s hard to distinguish the influences of genetics and environment from the eating habits that people develop over their lifetime, said Sonya Angelone, a San Francisco Bay Area–based spokesperson for the Academy of Nutrition and Dietetics.

However, she agrees that there is a genetic cause for cravings. Like 23andMe’s Shelton, she said the FTO gene plays a key role, since it affects levels of the hormones ghrelin, which makes people feel hungry, and leptin, which makes people feel full. Other important genes that influence appetite can interfere with how satisfied we are with food intake and can cause cravings, she said.

“There’s a lot that goes into it,” Angelone said. “What actually is a craving versus hunger versus just a bad habit is a little harder to define. It has to do with the reward center in your brain and what gets triggered when you eat. So it’s pretty complex.”

Craving certain tastes, like sweet or salty, at certain times can be a habit, she said. “Like after dinner, I want something sweet, or I want my cup of coffee, and then people just assume that it’s a psychological need, but it’s not, really. They’ve just conditioned themselves to crave dessert after dinner.”

Eating behaviors are complex. Along with genetics and environment, lack of sleep, nutrient deficiency, poor diet, low blood sugar, dehydration and stress can also contribute to cravings, Angelone said. Because there’s rarely a single factor contributing to cravings, people need to learn what brings on cravings, how to manage them and adjust their environment. But it’s OK to give in to sweet and salty cravings from time to time.

“This idea of perfect eating, I don’t even know what that is,” she said. “Does that mean you can’t ever have sugar or salty things? Sure you can. But what I tell people is use the word “manage.” Manage your cravings.”

Genetics may predispose someone to crave sugar or salt, but lifestyle changes help manage cravings and not reinforce unhealthy eating habits, Steinle said.

“You can blame your genes for liking it, but we have the ability to say, ‘Is this a healthy behavior?’ and modify it,” she said. “We’re intelligent, not just machines. If you love potato chips, you can alter your eating behavior if you so choose.”