Can we train our taste buds for health? A neuroscientist explains how genes and diet shape taste

Can we train our taste buds for health? A neuroscientist explains how genes and diet shape taste

Have you ever wondered why only hummingbirds suck nectar from feeders?

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Unlike sparrows, finches and most other birds, hummingbirds can taste sweet things because they have the genetic instructions needed to recognize sugar molecules.

Like hummingbirds, we humans can sense sugar because our DNA contains gene sequences that code for the molecular detectors that allow us to detect sweetness.

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But it's more complex. Our ability to perceive sweets and other tastes requires a delicate dance between our genetic makeup and the foods we encounter from the womb to the dinner table.

Neuroscientists like me are working to decipher how this complex interplay of genes and diet shapes taste.

In my lab at the University of Michigan, we delve deeply into one particular aspect: how consuming too much sugar weakens the feeling of sweetness. Taste is so central to our eating habits that understanding how genes and the environment influence it has critical implications for nutrition, food science and disease prevention.

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The role of genes in taste perception

As with hummingbirds, humans' ability to detect the taste of food depends on the presence of taste receptors. These molecular detectors are located on the sensory cells housed in the taste buds, the sensory organs on the surface of the tongue.

The interactions between taste receptors and food molecules create the five basic taste qualities: sweetness, savory, bitterness, saltiness and acidity, which are transmitted from the mouth to the brain via specific nerves.@media(min-width:0px){#div-gpt-ad-healthy_holistic_living_com-large-leaderboard-2-0-asloaded{max-width:336px!important;max-height:280px!important;}}

A diagram of a taste bud, showing different types of cells and the sensory nerve.
Julia Kuhl and Monica DusCC BY-NC-ND

For example, when sugar binds to the sweet receptor, it signals sweetness. Our innate preference for the taste of some foods over others has its origins in how the tongue and brain have been wired throughout our evolutionary history. Taste qualities, which signal the presence of essential nutrients and energy such as salt and sugar, send information to brain areas associated with pleasure. Conversely, flavors that alert us to potentially harmful substances, such as: B. the bitterness of certain toxins, associated with those that cause us discomfort or pain.

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While the presence of genes encoding functional taste receptors in our DNA allows us to recognize food molecules, our response to them also depends on the unique combination of taste genes we carry. As with ice cream, genes, including those for taste receptors, come in different flavors.

Take, for example, a taste receptor for bitterness called TAS2R38. Scientists found small changes in the genetic code for the TAS2R38 gene in different people. These genetic variants influence how people perceive the bitterness of vegetables, berries and wine.

Taste not only allows us to taste the wide variety of flavors of foods, but also helps us to distinguish between healthy and potentially harmful foods, such as: B. spoiled milk.

Follow-up studies suggest a link between the same variants and food choices, particularly with regard to vegetable and alcohol consumption.

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There are many other variants in our genre repertoire, including those for the sweet taste receptor. However, whether and how these genetic differences affect our tastes and eating habits is still being clarified. What is certain is that although genetics lay the foundation for taste sensations and preferences, experiences with food can profoundly change these.

How diet affects taste

Many of our innate feelings and preferences are shaped by our early experiences with food, sometimes before we are born. Some molecules from the mother's diet, such as garlic or carrots, pass through the amniotic fluid to the developing taste buds of the fetus and may affect appreciation of these foods after birth.

Infant formula can also influence dietary preferences later on. For example, research shows that infants fed non-cow's milk-based formula—which is more bitter and acidic due to its amino acid content—are more likely to accept bitter, sour, and savory foods, such as vegetables, after weaning than those who consume cow's milk-based formula. And toddlers who drink sweetened water prefer strongly sweet drinks as early as age 2.

The influence of food on our taste disposition does not stop in early life: what we eat as adults, particularly our sugar and salt intake, can also influence the way we perceive and potentially choose foods. Consuming less sodium in our diet reduces our preferred salt levels, whereas consuming more causes us to prefer saltier foods.

How taste works in the brain...

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How taste works in the brain – the science of taste

The same goes for sugar: reduce the amount of sugar in your diet and you may find the food sweeter. Conversely, as research on rats and flies shows, high sugar levels can dampen your sense of sweetness.

Although we researchers are still working to figure out the exact how and why, studies show that high sugar and fat intake in animal models dampens the responsiveness of taste cells and nerves to sugar, changes the number of available taste cells, and even flips genetic switches in the cells' DNA.

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In my lab, we have shown that these taste changes return to normal in rats within weeks when the extra sugar is removed from the diet.

Animal studies have shed light on how high sugar intake affects taste and eating.
Irina IlinaCC BY-NC-ND

Illnesses can also affect the taste

Genetics and diet aren't the only factors that influence taste.

As many of us discovered at the height of the COVID-19 pandemic, illness can also play a role. After I tested positive for COVID-19, I couldn't tell the difference between sweet, bitter, and sour foods for months.

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Researchers have found that about 40% of people infected with SARS-CoV-2 suffer from impaired sense of taste and smell. In around 5% of these people, these taste deficits persist for months and years.

Although researchers don't understand what causes these sensory changes, the leading hypothesis is that the virus infects the cells that support taste and smell receptors.

Train your taste buds for a healthier diet

By shaping our eating habits, the complicated dance between genes, diet, disease and taste can influence the risk of chronic disease.

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Beyond distinguishing between foods and toxins, the brain uses taste signals as a proxy to estimate the satiating power of foods. In nature, the stronger flavor of a food – in terms of sweetness or saltiness – is directly related to its nutritional and calorie content. For example, a mango contains five times as much sugar as a cup of strawberries and therefore tastes sweeter and more filling. Therefore, taste is important not only for the enjoyment and selection of food, but also for the regulation of food intake.

When taste changes through diet or illness, sensory and nutritional information can become “decoupled” and no longer provide our brains with accurate information about portion size. Research shows that this can also occur when consuming artificial sweeteners.

And in fact, in recent studies of invertebrate animal models, our lab has found that the taste changes caused by high dietary sugar intake lead to higher food intake by interfering with these food predictions. Above all, eat a lot
Patterns and brain changes that we observed in flies were also discovered in people who ate foods high in sugar or fat or had a high body mass index. This raises the question of whether these effects are also due to taste and sensory changes in our brain.

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But the adaptability of taste also has a positive aspect. Because diet shapes our senses, we can actually train our taste buds – and our brains – to respond and prefer foods lower in sugar and salt.

Interestingly, many people already say that they find foods too sweet, which is not surprising since between 60 and 70% of foods in the supermarket contain added sugar. Reformulating foods tailored to our genes and the plasticity of our taste buds could be a practical and powerful tool to improve nutrition, promote health and reduce the burden of chronic disease.

Monica Dus, Associate Professor of Molecular, Cellular and Developmental Biology, University of Michigan

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

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