Yacon syrup

The thickened juice of the Andean yacon root. Mildly caramel-like, it sweetens porridge, yoghurt and dressings. Contains FOS – but it's still a sweetener.

What is yacon syrup? Sweetness from South America

Sweetness is a constant topic in nutrition circles. In the cold Andes of Peru, people have grown an unusual plant for thousands of years: the yacon root (*Smallanthus sonchifolius*). The fat, juicy tubers look a lot like large sweet potatoes. Press the yacon and gently reduce the clear juice at a low temperature, and you get yacon syrup: a very dark, thick syrup with a deep sweetness and a soft, raisin-and-caramel flavour. What makes it interesting is its chemistry.

What's in it: fructooligosaccharides (FOS)

So why is this dark, caramel-like syrup different from other syrups? The answer lies in the carbohydrates of the yacon root:

• Fructooligosaccharides (FOS): raw yacon syrup consists of around **40 to 50 per cent** FOS. FOS are short chains of fructose that are linked in a way your body can't easily split. The human stomach and small intestine lack the enzymes needed to break them down, so this part of the syrup provides hardly any calories that your body can absorb.
• Glycaemic index: for the raw root, a glycaemic index of just 1 is often quoted, because of its high FOS content. Treat the syrup with the same care as honey or maple syrup, though – it's still a sweetener.

What researchers have looked at

FOS in the large intestine

Because almost half of a spoonful of yacon syrup isn't broken down by stomach acid or digestive enzymes, that part reaches the large intestine intact. There, gut bacteria such as lactobacilli and bifidobacteria ferment the FOS. As a by-product they produce *short-chain fatty acids (SCFAs)* such as butyrate. That's why FOS is counted as fermentable fibre.

A small study on body weight

In one study, women with obesity were given 1 to 2 tbsp of yacon syrup a day as a regular addition, well before their main meals. Researchers then tracked their body weight and waist measurements over several months. One idea is that the thick, fibre-like FOS make a meal more filling and change the mix of bacteria in the gut. It's a small amount of research, so don't read too much into it.

Important: start small

However much you like the syrup, don't start with two heaped tablespoons in your coffee or yoghurt. When the bacteria in your large intestine meet a large amount of FOS at once and start fermenting it, they produce a lot of gas – which can mean rumbling, bloating, wind or even sudden diarrhoea that lasts for hours. Always start small and slowly, with 1 modest teaspoon in the evening, for example in a cup of chamomile tea.