The new kid on the tongue

Umami -you’ve got to love the word! It almost sounds like the verbal equivalent of a wolf-whistle doesn’t it? And it’s of relatively recent coinage -Miss Heldon, my Grade 4 Health teacher with her tongue-taste maps and quadripartite flavour-world would never had heard it, let alone believed it. Everybody knew there were only 4 taste choices: sweet, sour, bitter and salty; we knew them like we knew the colours. There were no more choices -you couldn’t even imagine any. Period.

When you are young, things like that have a biblical authority about them; to doubt them was to risk derision. Taunting. Fights in the corner store after school. We took things seriously in Grade 4.

And truly self-evident things like tongue-maps and the times-table persist like family through the years. Even as an adult -long after the 1909 paper by its discoverer Kikunae Ikeda describing umami, was finally translated from Japanese into English in 2002- I still had difficulty understanding how I could have missed such a basic flavour all those years. I mean, it wasn’t like the deficit in red-green colour blindness or anything -it was there all along for each of us. And it wasn’t even hiding -well, not if you eat seaweed, anyway.

But the world is littered with details, and unless you find yourself in danger of losing face in an argument about one of them, it remains just another pebble in the gravel. And let’s face it, I suspect that few of us encounter our Grade 4 Health teachers anymore. So it sometimes takes a stroll through an unsuspecting app to stoke the fires of memory -to awaken the slumbering kraken. I find that the BBC Future section is as good as any path to wander along when I am caked in languor, and on one such amble, I found myself suddenly immersed in umami-world -although it was more of a stumble, than a target: http://www.bbc.com/future/story/20190503-the-mystery-taste-that-always-eluded-us

‘For centuries, humanity lived with the concept of sweet, salty, bitter and sour – but another flavour was hiding on the sidelines, writes Veronique Greenwood… umami taste behaves a bit differently from the others. It does not get stronger linearly with higher levels of glutamate and other substances that trigger it, the way that sweetness does.’ And, ‘It’s not just found in seaweed: we get a hit of umami from tomatoes, meat, broths, cheeses, and many other foods.’

Well, that hooked me. It turns out that the amino acid glutamate was an important component in producing the flavour. Given the controversy over MSG (monosodium glutamate of the Chinese Restaurant Syndrome fame) I was intrigued, and the dyspepsia of the too-many-chicken-chow-mein-dinners of my university days stole over me as I began to taste the article.

I learned that there were at least two other molecules that could also trigger the taste: inosinate and guanylate -both strangers to me. But, unlike umami’s resistance to strengthening in higher concentrations -unlike adding more sugar to increase the sweetness- ‘the effect of having two of these molecules in the same dish is synergistic.’ Curiouser and curiouser, eh?

And umami is not a mixture of two of the standard-issue tastes -say, saltiness and bitterness- because ‘there are specific receptors in taste buds that pick up on amino acids… In a way, it isn’t surprising that our bodies evolved a way to sense the presence of amino acids, since they are crucial for our survival. Breast milk has about the same levels of glutamate as the dashi broth [a broth made from seaweed and dried fish flakes] studied by Ikeda, so we are probably quite familiar with the taste before we can even walk.’

But, given the discovery of a new taste bud on an already well-studied tongue, are there other surprises in store for whoever wants to spend the time going over it with an even finer comb? Greenwood suggests that ‘Some researchers believe we may have a sixth basic taste for fat. There are some good candidates for fat receptors in the tongue, and it is clear that the body responds strongly to fat’s presence in food.’ An interesting thought, except that apparently, ‘by the time fat levels are high enough that we can actually taste them consciously, we tend not to like the flavour very much. So the question becomes, can something be a basic taste if we don’t really taste it, per se? How much of taste is about encouraging or discouraging us to eat something, and how much of it is the body, unbeknownst to us, keeping track?’ Wheels within wheels, it seems.

But I am reminded of a condition we occasionally encounter in my field of obstetrics: pica -a variety of eating disorder. The name comes from the Latin word for magpie -a bird with a seemingly undiscriminating appetite.

There are several types of pica, but the type one of my colleagues encountered in two or three of her Latina patients from the Los Angeles area, seemed to be amylophagia -the ingesting of raw starches such as laundry starch and even flour. I don’t know that she ever discovered enough about the practice to come to any conclusions, but the etiology seems to be quite complex. There is some evidence that it is linked to poor socioeconomic status in some communities, or that it might be consumed for medicinal purposes -for nutritional deficiencies of vitamins and minerals, especially. One of the more widely suggested associations with pica (involving clay, or even dirt), has been with iron deficiency anemia -a particularly common risk in pregnancy. And there is even some conjecture that there may be a change in taste and olfaction in pregnancy that favours the ingestion of cornstarch according to an article in the Western Journal of Medicine ( 2000 Jul; 173(1): 20–24).

But, whatever the reason, and whether or not it is of any value -or detriment- to the pregnancy, isn’t it interesting to think that the practice may be an attempt by the body to right a nutritional wrong? That maybe there could be an alteration of taste bud affinity to acquire the missing components? Or that maybe there are proto-buds lying fallow on some forgotten corner of the tongue just waiting for the call?

Perhaps we should be paying as much attention to the anatomy of the tongue as to the words it issues. Are you listening Miss Heldon… Somewhere?