Your estimate is off by almost an order of magnitude. 100g is not 10% of a person's weight. Maybe you meant 10% of calories.

Also, look at the comparison. It is seaweed! Wouldn't you expect that eating 10% of your weight in seaweed changes a microbiome? It is a massively different food than what we (or mice) typically eat - thus the microbiome has to adapt. I am not saying the discovery is not important - it is the right question, set up correctly.

Compare that to a human eating two slices of different breads for a week. The differences between bread are too subtle. The amount ingested is too little, the time is too short. Your microbiome is already set up for digesting bread. That's all I am saying -

I will stick to my story that there is very little chance that this would ever be sufficient to detect any change.