There's alot of confusion about vitamins and minerals these days.......
If you try and research the subject, its hard to find data that does not contradict the last piece of data.If you were to contact and ask a branded company,many will not disclose source or production method and many don't even reply,red flag!!! stop!!!
So, if we take iron as an example, we all know we could not digest a piece of iron in solid metal form,but if we take that piece of metal and place in soil/compost the beneficial aerobic bacteria, fungi and microbes very basically eat it,poo it out as food for a plant to consume. Guess who's meant to eat the plant??
When it passes through a plant it becomes extremely small and electrically charged,so its completely 100% absorbable for us humans and is now called a colidal mineral,
This process can also happen with running water weathering mineral rich Rock,one molecule at a time,so drinking wild water has more going on than just low chemical,it can have high levels of colidal minerals.Also adding rock dust to your garden veggie plot is a great option,but takes time to work.
Equally, certain parts of the ocean have perfect levels of minerals, the reason why sea veggies are so healthy,seaweed is ultra high in nutrients. Pink salt(my favourite source)is actually ancient sea water with high levels of nutrients,good absorbable cheap options.
Back in 60' sand 70's in the US there were quite a few organic plant dirived mineral/vitamin company's,so it was understood by the newage movement, unfortunately they were slowly priced out the game and the market became a monopoly and the drug lord company's turned towards synthetic and/or incorrectly processed forms.
Some of these forms can be absorbed in small amounts,when taken with a meal, but its low level and there's no clinical data that provides evidence that the body can actually used it to build and repair.
There's a famous story about a guy in the States who owns a portable toilet company,he reported that he found thousands of vitamins completely undigested within his toilets after a large event, brand name still intact!! We know the body also excretes most synthetics via urine.
So buying vitamins or minerals without really knowing what they are will only ever give you expensive urine :)
One of my many mentors is Dr Joel Wallach,he owns the fastest growing mineral company in the world and was the only guy not to sell to big farmer.Based in the US,he happens to be expert in many scientific disciplines related to this topic and is the only man to successfully sue the FDA regarding selenium as a cure for cancer,this is still the only thing you can claim in public as a cure.
Youngevity is the company and they have some of the best liquid and powdered minerals in the world,not cheap but they are the real deal and so is Joel wallach. There will be other company's, but ask questions and wait for answers.
One last thing.......just because veggies may be grown in soil "organically " it doesn't mean that it will have picked all the minerals we need,no plant on earth can make a mineral,it must pick it up from the soil and some soils are completely depleted of certain minerals or more often,there's too few microbes present to convert.......Dr wallach is all over the Internet,he's old skool but he has proven there are 90 essential minerals and nutrients for humans to cure any non-physical illness or prevent it in the first place.check him out if you want data, wallachfiles.com, youngevity.com and many presentations/interviews on Yt.
If you are in the UK forget Holland and barret, youngevity is available via uk and EU distributer now.
Hope this helps