Each molecule that has been shown to grow hair(not talking about some topical that grows in reality a few sprigs of hair) either stops LPS from entering the bloodstream or counters the rise in IL-17 from failing to do that.
The key is to use many different substances that fly under the radar of side effects.
Tacrolimus is no different
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Tacrolimus can reduce the production of IL-17 and the expression of Th17 cells, which mainly produce IL-17. Tacrolimus can also inhibit the pro-inflammatory effects of IL-17 and TNF-α on human keratinocytes.
Also, while sunlight is great for vitamin d production not everybody can convert it either. Somebody posted that study in hairlosstalk. Some have had great results with vitamin d so I wouldn't just broadly dismiss it as casually as you do.
There are other factors of vitamin d status also to consider:
Studies on the determinants of vitamin D status have tended to concentrate on input - exposure to ultraviolet B radiation and the limited sources in food. Yet, vitamin D status, determined by circulating concentrations of 25-hydroxyvitamin D (25(OH)D), can vary quite markedly in groups of people...
pubmed.ncbi.nlm.nih.gov
Studies on the determinants of vitamin D status have tended to concentrate on input - exposure to ultraviolet B radiation and the limited sources in food.
{Yet, vitamin D status, determined by circulating concentrations of 25-hydroxyvitamin D (25(OH)D), can vary quite markedly in groups of people with apparently similar inputs of vitamin D. }
There are small effects of polymorphisms in the genes for key proteins involved in vitamin D production and metabolism, including 7-dehydrocholesterol reductase, which converts 7-dehydrocholesterol, the precursor of vitamin D, to cholesterol, CYP2R1, the main 25-hydroxylase of vitamin D, GC, coding for the vitamin D binding protein which transports 25(OH)D and other metabolites in blood and CYP24A1, which 24-hydroxylates both 25(OH)D and the hormone, 1,25-dihydroxyvitamin D. 25(OH)D has a highly variable half-life in blood.
{There is evidence that the half-life of 25(OH)D is affected by calcium intake and some therapeutic agents.}
Fat tissue seems to serve as a sink for the parent vitamin D, which is released mainly when there are reductions in adiposity. Some evidence is presented to support the proposal that skeletal muscle provides a substantial site of sequestration of 25(OH)D, protecting this metabolite from degradation by the liver, which may help to explain why exercise, not just outdoors, is usually associated with better vitamin D status.