Tasting Notes: A Scientific Justification for Hating Kale

There is a new East-West arms race, and it is full of bitterness. Literally.

Since moving to the West Coast, I have been struck by the preponderance of bitter foods and beverages. The coffee, beer and lettuce producers here appear to be locked in a bitterness arms race with each other to see who can make the least palatable product, with no clear victor. It seems that the West Coast version of all of these products (think: dark-roast Starbucks, exceedingly hoppy pale ales, and kale) are significantly more bitter than their east coast counterparts (think: more traditional lighter roast coffees, lagers, and Boston Bibb).

Hops: beer’s bittering agent, liberally applied on the liberal left coast

What’s going on here? Are people’s taste buds addled from years of sipping California’s notoriously strong Cabernets? Is our future all about green smoothies and kale chips? And what are picky eaters (like, ahem, this blogger) to do?

It turns out I am not alone in opposing such bitterness, and the evolution of taste is on my side. And, moreover, the future may be friendly.

A taste of history

Humans can taste five distinct flavours: sweet, salty, sour, bitter and umami (otherwise known as “savoury,” the flavour of cooked meat, among other things). And each of our taste buds contains receptors for each of these  flavours, so taste sensation is not concentrated in certain regions of the tongue as previously thought but dispersed throughout. For example, we probably lick ice cream cones because they are too cold to eat with our teeth, not because sweet receptors are located at the front of our tongues.

We can also taste all five flavours simultaneously yet distinctly; if you were to eat something that contained all of the flavour elements, you would taste each in turn (and probably not enjoy it very much – I can’t imagine what such a food would taste like). Tasting is a multi-sensory experience, in fact. As any aspiring sommelier will know, flavour is produced both by the five taste sensations and the olfactory receptors in our nose, which give foods and drinks a much more complex and multi-layered profile. Temperature, texture, and auditory inputs such as crunch also influence our experience of “taste.” No wonder we love to eat.

Humans have such developed tasting abilities because we are omnivores with varied diets, and require a plethora of nutrients found in many foods to survive. Other animals do not require such diversity of nutrients, so cannot taste such variety. Pandas, who have evolved to eat almost exclusively bamboo, cannot taste umami. Cats and chickens “lost” the ability to taste sweetness at some point in their history.

How sweet it is

It is thought that our fondness for sweet foods was among the first tastes to be developed, because we need simple sugars as a fundamental building block of nutrition. Today healthy sugars and sweet tastes come from fruits and breads. Salty food indicates the presence of sodium (or lithium, or potassium), and a certain amount of sodium is necessary for our bodies to function, since humans lose salt through sweat.

Sour foods, such as lemons, are typically acidic (in the chemical sense) and a sour taste can signify that food is rancid. Sour is also good, however: humans need a certain amount of Vitamin C, found in sour foods, to survive, so our taste buds developed to seek this flavour out. An emerging theory is that our sweet and sour tastes evolved simultaneously from exposure to fruit, which contains both tastes. Both flavours are also present in fermented foods and cooked meat, the former being important in providing good bacteria to aid digestion and the latter in being more easily digested than raw meat.

Bitterness is the most complex receptor, and it is thought that humans can perceive 25 different kinds of bitterness. Bitter foods are frequently basic (again, in the chemical sense), and bitterness is an innately aversive taste. Babies will turn away from bitter foods – such as leafy green vegetables – just as they will naturally gravitate toward sweet ones. As one article I read succinctly put it:

“Many people do not like to eat vegetables—and the feeling is mutual.”

Bitter melon. Shudder.

Evolutionarily, our aversion makes sense. Plants secrete pesticides and toxins to protect themselves from being eaten. Even now, if we taste a strong bitter food, our bodies behave as though they are preparing to ingest a toxin, activating nausea and vomiting reflexes to protect us. Pregnant women are particularly sensitive to bitterness because their bodies are hypersensitive to the baby’s health. It is also now thought that small children have some justification for hating brussels sprouts and other green, leafy vegetables in that their younger taste buds are particularly sensitive, and averse, to bitter flavours. Picky eaters vindicated!

It’s a bird! It’s a plane! It’s … Supertaster?

A relatively recent theory that has the tasting world abuzz (ataste?) is the discovery of so-called “supertasters,” individuals with a greater number of taste receptors (the typical number of taste buds in humans can range from about 3 000 to over 10 000). Some experts also theorize that supertasters may have normal receptors, but more efficient neural pathways to process the tastes. They are more likely to be female, and of African or Asian descent, and some estimates put them at 25% of the population.

Supertasters are particularly sensitive to bitter flavours present in such foods and drinks as grapefruit, coffee, wine, cabbage and dark chocolate. They are also thought to be more sensitive to sour and fatty foods, which means they are usually slim, but their aversion to vegetables makes them more susceptible to various cancers. And they are most certainly susceptible to the ire of their parents, friends at dinner parties, and anyone else who tries to feed them.

Like an evil mutant flower.

Leaving a bitter taste in our mouths

So why would anyone, supertaster or no, desire to eat foods that humans have convinced ourselves over millennia are toxic and therefore to be avoided?

In fact, many scientists theorize that we only learn to like bitter foods after seeing the other positive effects they can have on us, often pharmacological ones. Consider coffee, which makes us more alert, and wine, which makes us more relaxed. This can be the only reason anybody with taste receptors eats spinach or kale, right?

A fondness for bitterness seems, in my entirely unscientific analysis, to centre on warmer regions, where these foods are traditionally grown, such as coffee, olives, grapefruit, and bitter melon. See, for example, a traditional Mediterranean diet pyramid, which contains several bitter foods.

A Mediterranean traditional diet pyramid

Perhaps more significantly, though, scientists have discovered a link between eating bitter foods and socioeconomic status. One study in France found that men who ate a greater variety of bitter foods were more likely to be well-educated and have a lower body mass index (BMI). Women who ate a greater variety of bitter foods also had lower BMIs and were less likely to have diabetes.

It would seem that bitter foods today pose less of a threat of toxicity and yield great health benefits (well, perhaps kale more than IPAs). Likely this rational reasoning is behind the West Coast health food craze, and indeed why bitter foods are more commonly consumed for their health benefits where populations are more educated and wealthier, as a whole.

Science will continue to play a factor as well. We may know in our heads that Brussels sprouts are good for us but still dislike the taste. Food producers will likely try to engineer foods to keep the benefits without the drawbacks. In fact, many foods are already “debittered” by the food industry, from oil to chocolate to orange juice.

So good news for West Coast dwellers, supertasters, children and those averse to toxins everywhere: one day you may be able to have your kale chips and eat them too — happily.

Kale: the world’s ugliest vegetable?  It’s coming for you!