Many of us describe ourselves as having a sweet tooth. But science is now unlocking the secrets of why having a well-developed taste and tolerance to bitter foods could have a wealth of health benefits. But even with their many health benefits, the bitterness of foods such as broccoli, spinach and turnip can put people off. Now new research finds that the taste perception of bitter foods can change the more they are eaten.
Australians do a poor job when it comes to eating vegetables with just seven percent getting in the recommended five serves each day. Eating more of these foods can be challenging when they often have an unpleasant, bitter taste making it difficult to promote the health benefits of vegetables. This is in stark contrast to the fat, sugar, and salt-heavy obesogenic diets typical of many Western countries and where taste plays a key role in the desirability of these foods.
Bitter is its own uniquely developed taste. Whenever you experience a bitter taste, like grapefruit or brussels sprouts, or even a cup of strong coffee, there’s a reaction happening in your mouth between the chemical compounds in the food and your tastebuds. This is what creates that bitter taste sensation.
Sensing bitterness is a primal way for our bodies to detect potential poisons, as many of these bitter chemicals are part of a plant’s defence system. Yet a small amount of these substances, which technically can be considered a poison at high enough doses, can stimulate the body’s defence system. This enhances our antioxidant system to protect against disease. And it is one of the reasons that many of the bitter foods such as broccoli, spinach and even coffee are increasingly being linked to good health. There’s also some evidence that bitter foods may work like prebiotics in the gut too.
Some people enjoy the flavour of bitter foods, while others find them hard to stomach. That’s because we each have a unique make-up of tastebuds and their sensitivity can vary. Taste though is not a fixed sensation, with sensitivity and perception able to change over time. Tastebuds tend to lose their sensitivity as we age, which explains why children usually spit out bitter foods at first – they’re too strong for them.
One mechanism that taste can change is through proteins found in saliva. Food is dissolved in saliva and from there is exposed to over 1,000 different proteins. In humans, salivary protein profiles are related to taste sensitivity and food preference. Salivary protein profiles are different in children with limited food selections compared to children with no such eating difficulties
Amazingly, what is eaten can change the make-up of the salivary proteins which can then alter the sense of taste. The modification of bitter tastes could be a defence system by salivary proteins to allow altering of the characteristics of the food.
To explore this link further, in research looking at bitter taste perception, rats were trained to detect decreasing levels of bitterness in water with quinine added to it. Quinine is what gives tonic water its bitter taste. The rats were then put on diets containing bitter chemicals designed to alter their salivary proteins or they were given a control diet.
The rats exposed to salivary protein-inducing diets had higher detection thresholds for bitter taste meaning they were less sensitive to it. So over time and with a change in salivary proteins, the bitter taste of the water declined as they tasted less of the bitterness in so it shows that they had gotten used to the taste. And I’ll link to the study in the show notes https://pubmed.ncbi.nlm.nih.gov/31053859
Now, I know this is a rat study, but the results do agree with what we intuitively know about our own taste preferences in that they can change over time as we change the level of exposure to a taste if we were for example to slowly reduce how much salt we add to food, or how much sugar we add to our beverages.
Another interesting thing about bitter foods is that they are also thought to help with digestion and even with the feelings of fullness after eating. For instance, stimulation of bitter taste receptors in the gut, yes we can actually sense bitter in our gut as well as our mouth, has been shown to trigger the release of hormones that control appetite and food intake. In one study, people who took capsules of a bitter compound an hour before an all-you-can-eat meal ate fewer kilojoules than when given a placebo so there certainly appears to be something to the story.
And when you look at the types of foods that are bitter such as spinach, broccoli, coffee, green tea, kale and cranberries – most of these are low in calories or have a low energy density.
This research helps to show that bitterness can be an acquired taste. Increasing exposure to bitter foods by eating more of them can change the taste perception of these foods meaning they’ll taste better and that means your health will be better for it – just give it a little time.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.