The food scene in Cardiff and The Vale of Glamorgan (Wales), with an emphasis on Local Food. I also tweet @sfnottingham
Saturday, 15 January 2011
Why do Jerusalem artichoke make you fart?
Today, I did my first bit of gardening of the year. I broke up some spring planting garlic and put it into pots, dug up some Jerusalem artichoke, and did some general tidying. The Jerusalem artichoke has been regenerating in the same place in the garden for a few years now. They reappear even if only small bits of tuber are left in the ground. It gives a splash of yellow when it flowers late in the season. Growing up against a back fence, it requires no looking after.
The plant has nothing to do with Jerusalem and is not an artichoke. It is native to America (consumed by Native Americans before Europeans arrived) and is in the sunflower family (Helianthus). Sunroot or sunchoke are better names but never caught on. The flowers are much smaller than the sunflower, because this plant is putting most of its resources into the tubers. These are a welcome vegetable in January when there is little else to harvest. I mainly use them in soups, although they are versatile and can be used in numerous ways. Last year I took to boiling them with potatoes for a Jerusalem artichoke-spud mash.
Here’s a brief extract (stripped of references) from The Biology and Chemistry of Jerusalem artichoke, the book I co-authored with Stanley Kays (CRC Press, 2008). I got to write the section on farting: the thing most people know about Jerusalem artichoke! Basically, its storage carbohydrate is inulin instead of starch, which breaks down into fructose sugars (instead of sucrose or glucose). This means it is valuable as a low-calorific food (inulin extracts are increasingly added to low calories foods), is useful in diabetic diets (neutral effect on blood sugar), and can be utilized by the “good bacteria” living in the lower intestine (inulin is included in probiotic drinks that contain cultures of these “good bacteria”).
From Chapter 6, page 106:
“Human digestive enzymes do not target inulin. Around 89% of the inulin and fructooligosaccharides that we consume, on average, remain intact in the small intestine. As it is not digested, there tends to be a lot of it in the large intestine after eating a meal rich in inulin. However, none reaches the stools, and only a small fraction occurs in the urine. This is because inulin is completely fermented by the microbial fauna in the large intestine, especially by bifidobacteria and lactobacilli. The digestion is accompanied by the production of hydrogen, carbon dioxide, and other gaseous products. This leads to an undesirable side-effect of eating Jerusalem artichoke and other inulin-rich food: flatulence.
The wind-inducing effects of Jerusalem artichoke have been known for many years. Although the tuber spread rapidly throughout France in the ten years after its introduction in 1607, it was not universally popular due to over-indulgence of the unfamiliar vegetable revealing its digestive downsides. Jean-Luc Hennig, in Le Topinambour et Autres Merveilles, writes of the less than complimentary nicknames the street sellers gave the tubers…. Meanwhile, in England….John Goodyer’s entry for Jerusalem artichoke in the 1633 edition of Gerard’s Herball concluded: In my judgement, which way soever they be dressed and eaten, they stir up and cause a filthie loathsome stinking wind within the body, thereby causing the belly to be much pained and tormented, and are a meat more fit for swine than man; yet some say they have usually eaten them, and have found no such windy quality in them”.
Right, I am off to cook some of those nutritious, nuttily-delicious, knobbly Jerusalem artichoke tubers. More later…