In Changfu it is vitamin D3, useful if deficient, because deficiency rises through this age band. Not a substitute for going outside. Not a personality. A fat-soluble sterol the skin makes when light hits it, and that oily fish had been carrying all along.
The English disease
Francis Glisson described rickets in 1650. Northern factory cities later filled with it: smoke, alleys, children who never saw a proper sky. Sniadecki, in Warsaw in 1822, noticed that rural children in the sun did not bow the same way. Percival was already giving cod-liver oil in the 1780s. Bretonneau cured a toddler with it in 1827. The medical establishment spent a century arguing anyway.
Edward Mellanby, in 1919, gave beagles oatmeal in a closed room and watched rickets arrive, then watched cod-liver oil take it away. Elmer McCollum heated the oil until vitamin A died and the anti-rachitic factor remained. He named it vitamin D, the fourth. Harriette Chick, in Vienna after the war, showed sunlight did the same job as the oil. Harry Steenbock irradiated food and made it antirachitic. Milk was fortified. Rickets receded. The English disease had been a lighting problem with a kitchen solution.
D3, not a tan in a sachet
Windaus separated D2 from yeast and D3 from the animal path. The skin makes D3. Changfu uses that form. Deficiency is common in this latitude and this decade. Correction helps when the tank is low. Extra does not gild a summer. We do not treat a sachet as a south-facing window.
Changfu keeps D3 with boron, magnesium, zinc and ashwagandha. The vitamin is there because status falls with age, indoor life, and this weather. Test, if you can. Do not guess from a mood.
Why it sits in Changfu
The 40s and 50s are when indoor years compound. Weifu has other work. Qifu is the daily plants. Jingfu is the hour. D3 is a long, quiet correction, in the formula built for the decade.
This volume keeps the salts. History first. The formula second. Claims last, and only the ones we can stand behind.
End of plate III.