The Bitter Truth About Antioxidants
President George H.W. Bush infamously declared in an interview with the New York Times in 1990 that “I do not like broccoli, I haven’t liked it since I was a little kid and my mother made me eat it. And I’m President of the United States, and I’m not going to eat any more broccoli”. It is also understood that First Lady Barbara Bush would always happily eat his share. So, there was still balance in the universe. Later, as perhaps of a point of political difference President Barack Obama indicated it was his favourite food.
But President Bush was far from alone, and there are LOTS of people who don’t like eating broccoli. The feeling, however, is mutual and broccoli and the rest of the green vegetables don’t want to be eaten by us.
I recently wrote that plants have gone to a lot of trouble to make fruit irresistible to eat. They have gone to an equal amount of trouble to make their leaves well just the opposite. The reason is, of course, that they need those leaves to convert sunlight to energy. And long before omnivore humans turned up and before the herbivores there were insects. And it is war, eat and be eaten, or poisoned as it turns out. Because plants have natural defences against being eaten – in broccoli and cabbage, brussels sprouts and kale there are natural pesticides called glucosinolates. They are toxic to insects and rats. Even cattle can get kale poisoning.
Now, nobody likes being poisoned, and we (and pretty much all other creatures) have evolved a defence mechanism against that. We have no less than five different taste mechanisms to detect poisons in food, lots of redundancy there – and they trigger the bitter taste. We can detect bitter at very low levels of concentration. For example, bitter quinine can be detected at 1/400th of the concentration required for sucrose. Some people are “super-tasters” (maybe President Bush was one?) who are even more sensitive to the bitter taste. There’s probably an evolutionary advantage to that, perhaps in ancient times they were tasting the king’s food and could pick up the poisoning faster and spit it out sooner.
So here, then is the dilemma…
1) Plants make chemicals to discourage us from eating them. Those chemicals are poisonous, and therefore we evolved the capacity to detect those poisons and not eat them (it also goes for rancid food, and a few other “off” items).
2) Those same chemicals in LOW doses are very beneficial, and these are now very much the “flavour” of the month. We call them not poisons but antioxidants. You see, in addition to plants providing nutrition, they also provide phytochemicals that “prevent disease at the molecular level”. Hence our current obsession with kale.
The problem is that if the plant has lots of phytochemicals (which is what we want in small doses), they don’t taste very nice. One solution was for the horticulture industry to breed and grow less-bitter plants. For example, brussels sprouts have been bred to have lower concentrations of glucosinolates. They are actually less bitter than those that your parents ate or made you eat when you were young. Good for eating but also reduces the potency. Also important to note is that too much of these good things is a bad thing. People have literally died from eating bitter cucumbers and squash). It is probably the case that the lower level of this natural insecticide makes the brussels sprouts more susceptible to insects. As a result, farmers might need more synthetic insecticide.
The other way to deal with the bitter flavour is in the cooking. The classic techniques that add sweet (which masks bitterness) of braising and caramelizing work best (try brussels sprouts roasted if you haven’t already). Pickling also works. Think the famous dill pickle.
Both strategies work, although, in the less bitter raw product, you then need to eat more of it to get the benefit. The latter requires a bit of thought and skill. That’s where we come in. Each week, our in-house Chef Mark Woodcock is designing recipes to make sure that the not so palatable “green veggies” taste amazing (and are good for you). We use all of the tried and true trickery of the various culinary traditions. We can even help the supertasters of the world to embrace the bitter and like it. Maybe even George Bush, if he were still with us.
These musings have been inspired by the article:
“Bitter taste, phytonutrients, and the consumer: a review “by Adam Drewnowski and Carmen Gomez-Carneros in the Am J Clin Nutr 2000;72:1424–35