Yes, fermented yoghurt has cultures (think Kefir, which is said to be more potent), but evidently sauerkraut has many more per spoonful - which is why I thought I'd give it a go.
Alas, autoimmune Hashimoto's Hypothyroidism is widespread. It creeps up slowly and... suddenly you find yourself in a mire.
Thanks for calling by, Shereen. Keep up with the yoghurt!