Prebiotics for strong bones | Inulin & lactulose
A diet with a relatively large amount of prebiotic dietary fibers such as inulin and lactulose can ensure that bones become stronger in the long term. That's what a sponsored human study, recently published in Sports, suggests.

Sports scientists from Waseda University in Japan gave 29 female athletes, who were active in various disciplines, a functional food every day for 12 weeks, which provided a few grams of milk protein, 1 gram of lactulose and 2.5 grams of inulin.

Lactulose is very similar to lactose. Lactose is a molecule with a glucose and a galactose unit, while lactulose consists of a fructose and a galactose unit.
Both inulin and lactulose are prebiotics. They are broken down by micro-organisms in the gut and converted into short-chain fatty acids, among other things.

There is virtually no lactulose in our diet. Warm milk is the only source we can think of so quickly. When heating milk, part of the lactose can be converted into lactulose through the heating process. Inulin is mainly found in leeks, onions and sweet potatoes. [J Nutr. 1999 Jul;129(7 Suppl):1407S-11S.]Sponsor
The product the researchers used came from the Morinaga Milk Industry factories. And of course you saw it coming: Morinaga paid for the research.

Consumption of the functional food containing lactulose and inulin reduced the concentration of TRACP-5b in the blood of the subjects by 18 percent. The concentration dropped from 430 milliU/dL to 363 milliU/dL.

The more TRACP-5b there is in the blood, the more active are the osteoclasts in the bone tissue. Osteoclasts break down bone tissue.

The researchers used scans to determine the subjects' bone density, but were unable to find any effect. That was to be expected. The subjects were in top shape, and 12 weeks is not long.
Inulin and lactulose supplementation stimulated the population of the benign Bifidobacteria in the gut of the subjects. The researchers suspect that the short-chain fatty acids produced by Bifidobacteria inhibit osteoclasts.

Sports (Basel). 2021 Jun 4;9(6):82.