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Crave Sugar? Maybe It's in Your Genes

Quote:

Scientific American
2 May, 2017

Crave Sugar? Maybe It's in Your Genes

Specific genetic variants have been linked to the sweet tooth

Why do we yearn for the explosive gustatory delight of sugar? Neural feedback loops, sensory pleasures and environmental factors like poor sleep all amplify our desire for a sugar rush. But new research suggests some of us—much more than others—may also be genetically attuned to crave such sweet sustenance.

An international team scoured the genes of more than 6,500 Danish people taking part in a large health study on heart disease. They found those who harbored one of two particular variants of the FGF21 gene were roughly 20 percent more likely to enjoy and seek out sugary substances. “This study gives us insight into the molecular basis of the sweet tooth—that’s probably the heart of it for me: Why do you have a sweet tooth at a biological level?” says Matthew Gillum, co-lead author and a metabolism researcher at the University of Copenhagen’s Novo Nordisk Foundation Center for Basic Metabolic Research. The findings were published Tuesday in Cell Metabolism.

FGF21 provides the instructions for making a hormone by the same name that is associated with food regulation in rodents and nonhuman primates. Yet this new work suggests FGF21 may modulate some appetites in humans, too. What’s more, this work also suggests the liver—the organ that secretes the FGF21 hormone and controls insulin resistance—may play a larger role in snack management than previously known as it produces this hormone and communicates with the brain.

To investigate a possible FGF21–food preference link, researchers combed through thousands of volunteers’ reports about their dietary preferences, alongside the results of their cholesterol and blood sugar tests. The team also genotyped the participants’ FGF21 genes, and found subjects who reported strong sugar preferences and consumed more of it were much more likely to have one of the two specific FGF21 variants. The same FGF21 alleles—gene versions—were also associated with increased consumption of other problematic substances: The researchers found an additional, weaker link between those gene variants and a higher prevalence of alcohol consumption and daily smoking.

The paper does not pinpoint exactly what neural pathway could be at work to explain those tantalizing relationships. But one area of the brain called the nucleus accumbens is widely considered ground zero for rewards, craving and addiction—and it is possible that cravings for sugar as well as these other substances could converge there, says David Ludwig, a professor at Boston Children’s Hospital who specializes in nutrition and obesity and was not involved with the new study. Because the Cell Metabolism work is observational, however, the FGF21–sweet tooth relationship is “more in the range of hypothesis-generating than definitive,” Ludwig says. He believes it is impossible to know if the subjects with or without these gene variants might differ in other, important ways.

Although nutrition experts have previously identified other internal factors that help control our lust for food, some elements that mediate this process and send signals about sucrose satiety have remained mysterious.

Gillum now thinks FGF21, like leptin—another hormone that regulates appetite—may suppress the neural response to rewards, both in terms of the desire to seek them and consume them“We are still working on why the liver would have evolved mechanisms to do this, but hypothesize it may be to limit excess sugar consumption—either to promote diet diversification or to prevent the [problematic] effects of excess sugar intake,” Gillum says.

There are many unanswered questions in the paper, such as why people with these gene variants and higher sugar consumption tended to have lower body mass indexes (BMIs) than their nonvariant counterparts—a surprising finding, considering the well-established relationship between higher sugar intake and obesity. “Exploring if there is some genetic determination at work in humans’ food taste preference can help guide us to understanding which populations may be especially at risk,” Ludwig says.

Next, Gillum hopes to launch further genetic studies into the effect of these variants on body weight and type 2 diabetes, among other questions. “In mice deficient in FGF21, what we’ve seen is that they eat basically twice as much sucrose as those with them,” he says. “We want to look at people who are completely deficient in FGF21 and answer, Will they be alcohol or sugar superfreaks?”

https://www.scientificamerican.com/...-in-your-genes/

Quote:

Gillum now thinks FGF21, like leptin—another hormone that regulates appetite—may suppress the neural response to rewards, both in terms of the desire to seek them and consume them“We are still working on why the liver would have evolved mechanisms to do this, but hypothesize it may be to limit excess sugar consumption—either to promote diet diversification or to prevent the [problematic] effects of excess sugar intake,” Gillum says.

I think the thinking on this is so muddy when it comes to reward. Want to decrease reward? Reduce dopamine. Or give people a drug the blocks endocannabinoid signalling. Food intake as well as general motivation to move decreases. Fighting obesity by depression.

Lean, healthy, annoying people who are spontaneously this way with no special attention to diet. What can these people do? They can go to a birthday party, have one slice of pizza, one bite of cake and ice cream--and actually enjoy that little treat, where most of us would probably just be too frustrated to really enjoy that.

I become annoying if my diet is sufficiently ketogenic. If I'm not eating this way, even if I'm eating fairly keen Atkins, then I'll binge on cheese, peanuts, pepperoni, I'll overeat highly palatable low carb foods, and find them unsatisfying. But if my diet has been tight, I can fit these foods into my macros, I can be happy with an ounce of cheese or nuts or peanuts, I can feel satisfied--which to me is the definition of reward. If anything I think the problem is that people will seek reward in a bag of potato chips--but the chips are actually low reward, because it takes such a large amount to reach satisfaction, or reward.

https://en.wikipedia.org/wiki/FGF21

Quote:

In liver FGF21 expression is regulated by PPARα and levels rise substantially with both fasting and consumption of ketogenic diets.

Stephan Guyunet has said that both a low fat diet and a low carb diet work because they are low-food reward. I realize "food reward" is a technical term, but I wish it had some relation to the word as used in English, is it too much to ask that it not mean the opposite of common use? Anyways, I don't think he's right. It's entirely possible that somebody will stop eating tasteless, low fat food at a lower calorie intake because there's just no reward to be had in eating much of it. But they might eat less of a low carb or ketogenic food because they're satisfied with less.

My bias may be showing here, it's entirely possible that there are forms of low fat diet could take that are more rewarding, by my rogue layman's definition, than the old low-fat snackwell's and chocolate chip and caramel rice cakes route.

I look at these kinds of studies and think "so what".

Jean

Quote:

Originally Posted by cotonpal

I look at these kinds of studies and think "so what".

Jean

I agree unless something conclusive comes out it doesn't make a difference..

There's no question in my mind that taste preferences are at least somewhat genetic. We have in our home both biological children and children genetically unrelated to my husband and me. I often think I could write a funny comedy sketch about taste preferences, but I suspect I'd be accused of being racist, when in fact, it'd just be a slightly exaggerated version of my every day life. :lol:

Quote:

Originally Posted by tess9132

I completely believe you, because even infants, who aren't quite sure what food is and get it in their mouth because that is where they put everything, have strong taste preferences. :)

It is my own theory that the further north one's genes, perhaps the more sensitive to sugars and starches, which would be relatively rare, and highly needed to put on fat for winter. Why else would we have two systems?

When I visited Rio, it was like Land of the Giants: i was head and shoulders above most of the Brazilians, and twice their width, too. And their food was mostly starches; it was like a Midwest potluck down there.