Yacon syrup is a functional food with one of the highest naturally occurring concentrations of fructooligosaccharide (FOS). FOS is a compound that tastes sweet, but cannot be broken down by the body’s sugar-digesting enzymes, meaning it is low in calories, and does not increase blood glucose.
Yacon syrup is extracted from the tuberous root of the Yacon plant (Smallanthus sonchifolius). The plant was originally domesticated by the Incas, and is native to the Andes.
Yacon syrup has become very popular for the role it can play in promoting weight loss. Regular supplementation with yacon syrup before meals may increase insulin sensitivity, which can slow or reverse the development of type 2 diabetes (1). It has also shown promise in reducing fasting glucose and cholesterol levels (2). Yacon syrup is known as a prebiotic and helps keep the digestive system healthy. Friendly bacteria species such as Bifidobacterium and Lactobacillus maintain a large population in the lower intestine when FOS is present, as it is a preferred food source (3). Yacon also prevents constipation. Undigestable FOS has a similar effect on the gut to soluble fibre (1). Fermentation of FOS in the colon by bacteria lowers pH. This encourages greater absorption of calcium from the gut into the bloodstream, which is important for bone health (4).
The main attraction of yacon syrup is as a weight loss aid or metabolism booster. In the best known scientific study of its effects, obese female subjects shed on average 15kg over four months with supplementation, versus a 2kg weight gain in an identical group taking a placebo (1). Yacon root is a source of antioxidants, which prevent cell damage, and tryptophan, an amino acid with antioxidant properties that can also play a role in sleep and mood regulation (5). Additionally, experimental studies in animals show that the phenolic acids present in the yacon root may boost testosterone levels by suppressing enzymes in the liver that break the molecule down (6).
Using yacon syrup in moderation is generally regarded as safe, although many countries ban its use in infant formula. Large doses have been known to cause digestive problems such as diarrhoea and flatulence. Although early studies are encouraging, there is little information regarding the benefits of yacon syrup supplementation in healthy athletes. Some proposed benefits of this supplement, like testosterone boosting ability, have not yet been tested in humans.
A dose of 0.14g syrup /kg body weight/day was found to be effective in boosting metabolism and promoting weight loss. This is the equivalent of 9.8g/day for a 70kg person. The same study recommended breaking this into two doses and taking each an hour before eating (1). Other sources recommend taking the supplement with food. It is thought that dosages of up to 20g of FOS per day are generally tolerated well (7).
Yacon syrup is sold as a single-ingredient product, however may be dehydrated or powderised in time to be put into fat loss supplements.
Yacon syrup will stack with anything. As it increases calcium absorption, many people recommend stirring it into yoghurt, smoothie, or high calcium protein shake for a delicious low GI snack with multiple benefits.
(1) Genta S, Cabrera W, Habib N, Pons J, Carillo IM, Grau A, Sánchez S: Yacon syrup: beneficial effects on obesity and insulin resistance in humans.