When I imagine my childhood self sitting at the dinner table, I shake my head at all those delicious onions she pushed to the side of her plate in protest. Now that I consider them a necessary addition to almost every meal, I wonder how something once so repulsive to my taste buds could tantalize them years later.
Think about the treats you couldn’t get enough of as a kid. Chances are, they were full of sugar and would turn your stomach as an adult. (How else would you explain the popularity of Pixie Stix?) Similarly, the foods we consider treats now—well-aged cheeses, dark chocolate—probably didn’t taste that great to us as children. So what happens inside our mouths that causes such varied taste preferences throughout life? As it turns out, the steady decline in taste bud receptivity that happens with age actually makes more flavors palatable.
Papillae and Pickiness
Adults’ mouths contain about ten thousand taste buds that perceive five flavors—sweet, bitter, salty, sour, and umami, a “savory” flavor associated with foods containing MSG and other glutamate derivatives. Contrary to what people think of when they imagine taste buds, they’re not the tiny raised bumps we see on our tongues; those are called papillae and they house clusters of taste buds. They’re also what give so-called supertasters, people with a heightened sense of taste, their sensitivity—their papillae are packed more densely than the average person’s.
Taste buds are found mostly on our tongues, but not exclusively; some live in the back of our throats, on the sides of our mouths, and so forth. That’s not the case for kids, though—from birth, we start out with thousands of taste buds all over our mouths. As a result, flavors are much more intense for children than for adults. Childhood is often associated with periods of picky eating, but kids don’t think of themselves that way, at least not according to a University of Copenhagen study in 2008. It’s just that their taste buds require less stimulation than those of adults.
The Ravages of Age
When food enters the mouth, it activates the receptor cells that live on taste buds. Food particles hitting the cells are turned into messages carried to the brain via nerves. There, the brain decodes the message into whatever flavor’s being tasted. Receptor cells in the nose do the same thing once food aromas hit them. (That’s why sense of smell is such an important part of tasting: smell and taste work together to give the brain an accurate picture of what we’re eating.) These receptor cells need a certain amount of stimulation—in this case, food tastes or smells—to get the most flavor out of food. As we get older, the more stimulation we need.
It also doesn’t help that we lose taste buds as the years go on. Adults may have ten thousand to work with, but we were born with many more than that. Like all cells, the ones in the mouth eventually wear out and die, only to be replaced every one to two weeks. But one consequence of aging is that some cells aren’t ever replaced, which could explain why our sense of taste seems to change over time. However, a 1997 study at Tohoku University School of Dentistry didn’t find enough of a difference between the number of taste buds among various age groups to pinpoint that theory as the reason. After analyzing 241 cadavers between the ages of zero and ninety-seven, the Tohoku researchers found that taste receptor (another word for taste bud) and receptor cell densities did vary significantly: younger bodies contained higher densities than older ones.
A University of Western Sydney study conducted in 2002 also showed a difference in taste bud size between children and adults. Researchers found that the young participants, eight- to ten-year-old males, had greater papillae density than adults, which was linked to their increased sensitivity to sugar. The aforementioned University of Copenhagen study, which surveyed 8,900 school-age volunteers, found that the predilection for sweets starts dwindling once people hit thirteen or fourteen. Interestingly, that’s when sensitivity to sour tastes starts up, which could be why we become more gastronomically open-minded around that age, too.
Spicy, Smoky, Moody
Taste buds decrease in population and density as we age, but other factors contribute to our diminishing sense of taste as well. Numerous studies have attributed a poor sense of smell and taste to smoking cigarettes. Frequently eating spicy foods can damage taste buds; the same goes for hot beverages. Taste buds responsible for certain flavors are scattered all over the mouth, but since they all have the ability to detect more than one flavor, losing a few here and there affects overall taste.
Flavor recognition might also be affected by mood changes. A 2006 study at the University of Bristol and published in the Journal of Neuroscience found that volunteers given antidepressants showed a significant improvement in sense of taste, compared with their sensitivity levels before taking the pills. This discovery could explain why loss of appetite is such a common symptom of depression.
Before reading about taste buds, I assumed that mine and everyone else’s evolved over time, seeing as we tend to trade ultrasweet snacks for more-refined fare. But even though young people experience food flavors more intensely, frequently exposing kids to new foods will help them develop a taste for them. Our understanding of flavor comes not solely from genes, which determine taste bud configuration and specialty, but also from environment—our past experiences with food. Perhaps if onions hadn’t had such negative connotations for me as a kid (because they were prepared only one way in my household every time), I wouldn’t have discovered my love for them so late in life. Then again, maybe only mature individuals can appreciate such flavors. Kids might have a stronger sense of taste, but if that means preferring ultrasugary snacks like Pixie Stix, I’ll gladly take muted taste buds and extra red onions.