Vegetables harbor potent bitterness as their innate defensive mechanisms.
Many plants safeguard themselves from predators through using bitter compounds. However, most people dislike the taste of bitter vegetables. Over time, these bitter compounds have been selectively bred out, making the plants more susceptible to pests. A shift in perspective is necessary.
Nowadays, popular vegetable varieties have a more pleasant taste due to the elimination of less palatable bitter compounds through selective breeding. Regrettably, this breeding has left these plants vulnerable as they are now also preferred by pests like slugs and fungi. "Farmers might encounter fewer problems with some older varieties," suggests Nicole van Dam from the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. For instance, there's a type of cabbage that contains fewer bitter-tasting glucosinolates, but is more susceptible to infestation by threadworms (nematodes). Other plants like chicory and Brussels sprouts have also lost their bitter compounds.
Between the 1980s and 2010s, there have been extensive efforts in the food industry to eliminate bitter compounds in plants and create milder varieties through breeding and cultivation methods, according to the German Nutrition Society (DGE). "For instance, the decrease in per capita beer consumption since 1980 has been partially offset by attracting new consumers with milder beer types and beer cocktails."
Fewer Bitter Compounds, More Pesticides
The loss of defense mechanisms in many varieties is the outcome of breeders' long-standing focus on appearance. "If you eliminate a plant's defenses, you must protect it in other ways," explains van Dam. "You need more pesticides." Organic varieties are an exception, as their breeding also focuses on using fewer pesticides and synthetic fertilizers. However, synthetically-fertilized plants lack the necessary immunity training, accelerating the issue of dependency on pesticides.
Breeders currently pay more attention to natural defense mechanisms, as reducing excessive pesticide use is necessary. Even for vegetables where the bitter compounds are not appreciated due to their infrequent toxic effects, there are options: For example, zucchini breeding can focus on creating fewer bitter fruits instead of leaves. "This way, predators are deterred from attacking the young plant, and pesticides are needed less, only when the fruits appear."
On social media, numerous videos show babies reacting to something bitter with disgust. Recently, researchers discovered that fetuses dislike the smell of cabbage but enjoy that of carrots. According to scientists at Durham University in the UK, fetuses may already be subject to conditioning effects. "There's an innate aversion to bitter, similar to an innate preference for sweet," explains Maik Behrens of the Leibniz Institute for Food Systems Biology at the Technical University of Munich. Babies avoid ingesting toxic bitter substances and later learn which bitter things they can safely consume.
While there are many non-bitter toxins, like those found in the death cap mushroom, and many harmless bitter substances, Behrens notes that there are also highly toxic bitter substances, as well as carcinogenic ones that accumulate in body fat with regular consumption.
Cucurbitacins, found in cucumbers, melons, pumpkins, and zucchinis, are among the toxic bitter substances that can be harmful in large quantities. A couple of years ago, a 79-year-old man died after consuming an extremely bitter homegrown zucchini, despite its unpalatability. His wife survived. Such cases are extremely rare, says Behrens, "the dose makes the poison."
Artichokes, hops, gentian, endive, chicory, radicchio, and dandelion are among the plants that contain bitter substances, according to the German Society for Nutrition. Their health impacts range from beneficial to toxic or even fatal.
Bitter substances are not chemically identical but all activate the taste cells responsible for bitterness. Twenty-five bitter receptors have been identified, with four to eleven active in each receptor cell.
Researchers have discovered bitter receptors in many other body tissues, including the heart and brain. In the digestive tract, they are involved in stomach acid production and hormone release, while in the colon, they contribute to diarrhea as a defensive mechanism. In the airways, bitter substances promote the release of substances that fight bacteria and speed up the transport of particles like bacteria cells out of the lungs.
Scientists have discovered that certain bitter substances relax the smooth muscle of the bronchi, widening them. This effect could potentially be used in asthma medications that may be more effective than current ones, says Behrens. Many other functions in different tissues are still unclear.
Many folks often screw up their faces when tasting coffee for the first time, but the positive effects of caffeine, such as boosting alertness, usually overcome the bitterness in the end, as Behrens explains. Habituation also plays a significant role in other foods, like beer. In the northern regions, people tend to prefer more bitter varieties. "There's a tolerance for bitterness that depends on one's mindset and experiences," Behrens adds.
The complexity of food flavors escalates when bitterness is paired with sweetness, for instance, in dark chocolate, as per the German Nutrition Society (DGE). Bitterness is currently making a comeback, evident in the supermarket beer selection and backed by study findings. There's increasing evidence of various health advantages associated with bitter substances, particularly when consumed in a food matrix, such as vegetables and fruits, rather than in isolation and excess concentrations.
Bitterness lowers cholesterol
A specific group of saponins, including those found in legumes, herbs like rosemary and sage, and oats, create insoluble complexes with cholesterol and bile acids in the digestive tract. This may help lower cholesterol levels in the blood, according to the DGE. These substances may also exert anti-cancer and antibiotic effects, but in high doses, they can become toxic or even lethal.
Health experts advise against consuming these substances in supplement form because their effect is often dependent on the interaction between various substances and the metabolic pathways of the plants. "Eating vegetables and fruits is better than taking supplements," emphasizes van Dam. And for many bitter substances, the potential toxic or carcinogenic effects are not yet fully understood, making deliberate consumption in powder or tincture form risky.
Bitterness against nail-biting
Consuming excessively spicy food can be hazardous, possibly even fatal - but is there also a dangerously strong "bitter"? There's no analogous shock effect, but some of the over 1,000 synthetic and natural bitter substances listed so far have a taste so intense that even the most die-hard bitter fan steers clear. One such example is denatonium benzoate, which is used in alcohol denaturing, cable impregnation, and nail-biting remedies, as Behrens explains.
Amarogentin from yellow gentian is also incredibly bitter and serves as a standard for measuring bitter taste. If one gram of amarogentin were dissolved in 58 million liters of water, it would still taste bitter.
In light of the changes in vegetable varieties over the years, farmers might find it beneficial to consider using older, less palatable varieties that contain more bitter compounds, as they are often less appealing to pests like slugs and fungi (Farmers might encounter fewer problems with some older varieties). The elimination of bitter compounds in plants through selective breeding has led to a reliance on more pesticides, as the loss of defense mechanisms leaves them more vulnerable (If you eliminate a plant's defenses, you must protect it in other ways).
