The bitter wind of Brussels sprouts

It’s that time again; that most controversial of vegetables is appearing in UK shops. I am referring of course to Brussels sprouts, feared and hated by some, lauded by others. Not only is it peak growth season for sprouts but, for reasons that are obscure to me, it has become traditional for many families to include Brussels sprouts as part of their December 25th lunch menu. The upshot of this is that a quarter of the annual UK consumption of Brussels sprouts (40,000 tons in total) occurs in December.

So, what is it about this humble vegetable that raises such passion? Speaking personally, and I would guess this is true for others, I have never fully recovered from the childhood experience of overcooked boiled sprouts, bitter, sludgy, sulphurous and barely green. Part of the problem is that brassicas and particularly Brussels sprouts contain bitter tasting compounds called glucosinolates. These sulphurous compounds are thought to act as natural pesticides protecting the plant from insects. Humans find the glucosinolates bitter and this contributes to the bad reputation of sprouts. Worse still, when sprouts are boiled, glucosinolates are released in to the cooking water where some break down to smelly sulphurous compounds and that’s the odour we all remember. Much of the odour problem can be avoided by following Nigel Slater’s maxim: “The trick is to keep them well away from boiling water”.

To be fair to sprouts, they do not taste bitter to everyone and this variation seems to be, at least in part, down to genetics. As long ago as 1930, it was realised that the ability of humans to taste bitter substances had a heritable component. People who could detect bitter substances were very likely to have other family members with the same ability. The family link was so strong that it was used as a paternity test before DNA testing was available. Now we know that detection of bitter taste depends on both the number of taste buds on our tongues and the presence of particular isoforms of receptors on the taste buds that detect the bitter substances. As a result some people taste the bitterness of Brussels sprouts more than others, accounting in part for the differences in opinion about the vegetable. Children also seem to have a greater ability to detect bitter taste compared to adults so perhaps they are not so annoyingly fussy after all. The bitterness of sprouts may, however, be a thing of the past as the agrochemical companies have been working hard to breed new sweeter varieties, one of which is on sale this Christmas.

There is a further and perhaps even darker side to sprouts: the “windiness” that some people experience after eating Brussels sprouts. You probably didn’t want to know this but Sainsbury’s has compiled a “Top of the Pops” of windy vegetables: sprouts made third place beaten only by Jerusalem artichokes and parsnips. According to the Naked Scientists, the “windiness” of sprouts arises because our stomach and small intestine lack the molecular machinery to digest them fully so they arrive in the colon only partially digested. Bacteria in the colon do contain the correct chemical scissors so they set to work on the sprout remains and produce gas. To add to the problem, when the sulphurous compounds in sprouts are broken down they lend the gas an unpleasant odour. I leave the rest to your imagination or experience.

A growing band of sprout supporters, however, ignore the windy bitterness in favour of the health-promoting properties of these mini cabbages. In particular, they hail sprouts for their high content of both vitamin C and vitamin K. We are all urged to eat fruit for its vitamin C but sprouts contain, on a weight for weight basis, twice as much vitamin C as oranges. Vitamin K is not so well known but it plays an important role in blood clotting, facilitating wound healing; it may also help build strong bones. Green leafy vegetables, especially sprouts, are good sources of this essential nutrient. For most people, the high vitamin K content of sprouts is a healthy bonus but it can cause problems if you are taking anticoagulant drugs. An extreme example of this effect occurred to an Ayrshire man with a mechanical heart who was taking anticoagulants to prevent blood clots. In December 2011, he was rushed to hospital because his anticoagulants had stopped working. Apparently he had eaten a large plate of Brussels sprouts and the pro-coagulant vitamin K had counteracted the effects of his drugs.

Lastly some Brussels sprout trivia:

The Guinness World Record for eating the vegetable is held by Linus Urbanec of Sweden. To win the record, he ate 31 sprouts in one minute!

Francis Crick met his second wife, Odile in 1945 when she spilled a bag of Brussels sprouts on the floor of the office where he was temporarily working. He helped her pick them up, asked her out and was refused.

Sprouts grow on their stalk in a helical pattern as shown in the picture below. Perhaps Crick’s unexpected encounter with Brussels sprouts gave him an early clue about the structure of DNA!