As for the chewing, what I’ve been doing is buying those big tubs of chewing gum and taking one just after drinking Huel. That way it still simulates chewing, keeps the jaw muscles sharp and teeth healthy, plus freshens my breath after the Huel.
In terms of vit d the NHS say “do not take more than 25 micrograms (0.025mg) a day” Huel contains 15 micrograms.
Also these are based on you are consuming 2000 cals of Huel per day, which most people won’t on a consistent basis. I use Huel for about 60% of my meals.
Compare this to someone who consumes a “normal diet”, most people won’t calculate their micro nutrients intake, so they don’t know if they are consuming too much or too little. Plus many people take a 100% complete multi vit on top of their regular diet.