We hear a lot about how we need probiotics (pro-life bacteria) for a healthy microbiome in our colon, but far less about what are called prebiotics - the soluble fibre that is a food for these gut bacteria. Probiotics need prebiotics. Hence WE need prebiotics - and we get them from foods we eat.
This prebiotic food comes from indigestible soluble fibre found in plant foods as inulin, oligofructose and oligosaccharide (chains of glucose molecules). Prebiotic rich foods include: most root vegetables, garlic, onion, shallots, leeks, artichokes, asparagus, chicory root, dandelion root, bananas, whole grain wheat, psyllium husk, acacia gum - and this tuber shown here.
No, these are not sweet potatoes. They are yacon tubers, a traditional crop of the original Peruvian people, who used it to lower blood sugar in those with diabetes and to improve digestion. The leaves also have medicinal uses. Research in the last 10-15 years has identified the active constituents in yacon that
Yacon tubers contains 40-50% prebiotic fructooligosaccharides (FOS), inulin, and a small amount of fructose, glucose and sucrose. Because FOS cannot be absorbed by the body , it is naturally low in calories, about 1/3 of that of sugar (about 133 cal per 100g). Non-FOS sugars remaining in the plant are absorbed slowly into the bloodstream, which keeps blood sugar low.
The anti-diabetic and weight-loss effects of ingesting yacon are evidenced by these results from a double-blind, placebo-controlled clinical trial with 55 obese premenopausal women with cholesterol problems, insulin resistance and a history of constipation (Genta etal, 2009):
Over 120 days (4 months), all women were advised to eat a low-fat diet and mildly restrict calories. 40 of them were given yacon syrup, while 15 women were given another type of syrup with no active ingredients (placebo).
Women in the yacon syrup group:
lost 15 kg on average
lost 10 centimeters off of their waist
Body Mass Index (BMI) went from 34 to 28 (From obese to overweight)
Stool frequency increased from every three days to daily, effectively curing them of constipation
Fasting insulin levels went down by 42%
Insulin resistance went down by 67%.
LDL (the “bad”) cholesterol went down by 29%.
Women in the placebo group:
For myself, I grow a small crop of yacon in a bath tub and large pot, and make batches of shelf-stable dehydrated yacon chips to snack on when I fancy something a bit sweet (they have a sweet gingery-pear flavour). I do already have a prebiotic rich diet, but when I do have some gut-trouble after eating something that affects me adversely, I'll reach for some health-ful kombucha (probiotic drink and detoxifier) and yacon (prebiotic), without needing to buy a probiotic supplement.
For others, with irritable bowels and following a low-FODMAP diet, these FOS rich foods should be introduced slowly, starting with small doses and gradually increasing the amount consumed.
Interested? Look for yacon supplements in capsule form; buy yacon syrup from some wholefood suppliers, or grow some yacon yourself. Doing so will give you edible tubers that, after washing, can be sliced or grated raw into salads, juiced or dried (use a lemon juice or ascorbic acid solution to prevent the cut yacon oxidising to an interesting green colour!) This is a gut-healthier alternative to high sugar dried fruit and fruit juices, still very palatable for children.
Here's some more information about buying rhizomes, growing and using yacon.
Here's some more of my information about this marvellous plant food.