This story has been in the news lately and I thought I'd have a close look at where it originated. It was research conducted on how functional foods might improve a condition called Alopecia.
The paper (if you want to read it) is titled:
Do Kimchi and Cheonggukjang Probiotics as a Functional Food Improve Androgenetic Alopecia? A Clinical Pilot Study.
and if you really want to read it go here: https://www.ncbi.nlm.nih.gov/pubmed/31385480
So is it true? Well it's one study so far that tested a new probiotic product made with these ingredients from a kimchi and cheonggukjang probiotic product: culture medium with fermented bacilli of kimchi and cheonggukjang (Leuconostoc holzapfelii, Leuconostoc mesenteroides, and Lactobacillus sakei; 99.7%), persimmon vinegar (0.1%), Hasuo extract (Pleuropterus multiflorus; 0.1%), and extract of Korean black soybean (Rhynchosia volubilis Lour; 0.1%).
Hair was seen to grow at ~0.07 mm per month which isn't much but to those with Alopecia it may be a lot. 5 participants showed no change but the rest had hair growth of up to 6cm in 4 months. They believe that the underlying reason for hair growth such as the actions of the live bacteria in the individuals gut. This appears to have stimulated the blood flow to the scalp and promoted hair growth. This is a great study but they also recognise that it is early days. KimChi is a fermented food and is good for you regardless. We should all be having some fermented food in our lives :).